Providing Access for Large Trucks Special Report 223 (1989) / Chapter Skim
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Transportation Research Board National Research Council NAS1 NAfl lQ
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Special Report 223 Providing Access For.
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Transportation Research Board Special Report 223 mode 1 highway transportation subject areas 12 planning 51 transportation safety . 53 vehicle characteristics Transportation Research Board publications are available by ordering directly from TRB.
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Committee for Truck Access Study ROLAND A OUELLETFE, Eno Foundation for Transportation, Inc., Westport, Connecticut, Chairman ROBERT G
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BARBARA HARSHA, National Association of Governors' Highway Safety Representatives, Washington, D.C. JAMIE MCLAUGHLIN FISH, Committee on Public Works and Transportation, U.S.
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Preface THE SURFACE TRANSPORTATION ASSISTANCE ACT of 1982 expanded the federal role in regulating the size of heavy commercial vehicles and introduced the concept of a designated National Network of major trunk roads for heavy truck travel. Controversy ,over the extent of "reasonable access" that could safely be provided off this National Network to the longer and wider vehicles authorized by the act gave rise to the congressional mandate for this study.
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Contents Executive Summary . 1 Introduction ............................................
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6 Highway Design and Accident Risk ........................127 Important Geometric Features, 128 Relationship Between STAA Vehicle Operating Characteristics and Highway Geometric Features, 130 Findings, 149 Implications for Developing Access Policies, 151 7 Traffic Operations and Safety ............................. 155 Measuring the Impact of Heavy Trucks on Highway Capacity, 156 Factors Affecting STAA Vehicle Impact on Traffic Operations, 157 Summary, 167 8 Highway Condition .......................................
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Executive Summary S TATES HAVE REGULATED the size of commercial vehicles since the early 1900s. The trends have been toward ever larger trucks, mirroring improvements in the highway system and vehicle technology, and toward growth in the volume of freight moved by trucks.
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PROVIDING ACCESS FOR LARGE TRUCKS Assistance Act of 1987, requested that the Transportation Research Board of the National Research Council conduct a study on a nationwide policy for provision of reasonable access. The study committee considered several policy options, including uniform standards for access based on such factors as distance from the National Network, type of highway, and roadway characteristics.
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Executive Summary about the adequacy of specific highway design features in relation to the operating performance of STAA vehicles; the tools for making these assessments are available. Recommendation The FHWA should require states to adopt and use procedures based on safety and engineering considerations to assess the adequacy of highways to accommodate STAA vehicles.
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PROVIDING ACCESS FOR LARGE TRUCKS Vehicle Handling Characteristics Findings The safety of STAA vehicles cannot be determined directly from accident records but can be examined by assessing the handling and performance of the longer and wider STAA vehicles on highways with different geometric characteristics. Offtracking is the performance characteristic that is the most noticeably and measurably different for STAA and pre-STAA vehicles.
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Executive Summary Recommendation The committee urges the Congress to clarify whether states have the authority to restrict kingpin-to-rear-axle dimensions on the National Network as well as its access routes under the provisions of the STAA. A small majority of the committee further recommend that all states be encouraged to adopt a maximum kingpin setting of 41 ft (measured from the kingpin to the center of the rear trailer axle or group of axles)
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PROVIDING ACCESS FOR LARGE TRUCKS Access to Service Facilities Finding Providing access to service facilities has not been raised as a problem by government or industry. Many states now allow STAA vehicles to travel a short distance, generally ranging from 1 to 3 mi, from the National Network to reach service facilities.
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Executive Summary vide technical information that is pertinent to evaluating access requests; and, as required, coordinate industry requests for access that involve local government review, establish a time frame for completion of reviews, and create mechanisms for resolving conflicts. Implementation of Access Policies Finding Access restrictions are generally not perceived as arbitrary when clear evaluation criteria are applied in a timely and consistent manner.
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PROVIDING ACCESS FOR LARGE TRUCKS carriers maintain operating facilities. This definition is not intended to supersede existing bans or preclude new bans on combination truck travel, such as those on through travel on residential streets, weightposted roads or bridges, or roads not deemed appropriate for access on the basis of safety and engineering considerations.
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1 Introduction T HE U.S. ECONOMY DEPENDS heavily on trucks for moving goods and materials.
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10 PROVIDING ACCESS FOR LARGE TRUCKS proposed motor fuel tax increases. The federal regulations preempted more restrictive state vehicle size and weight limits and liberalized various vehicle size and weight provisions.
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Introduction11 costs or other measures of productivity for various segments of the trucking industry. As appropriate, related issues of permitting, enforcement, and data availability and reliability may be addressed.
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12 PROVIDING ACCESS FOR LARGE TRUCKS key benefits of their use; the extent to which state and local access policies restrict their use; and the costs of these restrictions. Safety Congress identified safety as the primary criterion to guide access decisions.
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Introduction 13 traffic operations under various traffic and highway conditions. Projections of the expected volume of STAA traffic by road type were not developed, but information about the expected use of STAA vehicles was drawn from interviews with motor carriers and shippers; segments of the industry most likely to increase their use of STAA vehicles were identified; and implications for travel on access roads were defined.
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14 PROVIDING ACCESS FOR LARGE TRUCKS policies. In the final chapter the pros and cons of alternative access policies are compared in light of these impact assessments and recommendations are provided on minimum requirements for access that, in the judgment of the committee, will assure a reasonable balance between safety and productivity.
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2 Historical and Regulatory Overview T RUCK ACCESS BECAME AN ISSUE after passage of the Surface Transportation Assistance Act (STAA)
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16 PROVIDING ACCESS FOR LARGE TRUCKS broader context, the liberalization of truck size regulations authorized by the 1982 STAA and the related question of truck access become simply another step in a continuing effort to balance industry productivity with the effects of truck travel on safety, traffic operations, and highway condition. State Regulations State governments have regulated motor vehicle dimensions since the early 1900s.
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Overview17 tions, particularly those related to vehicle weight, was to protect the federal investment in the Interstate system. The only size restriction established by the act was a maximum vehicle width of 96 in.; limits on vehicle length, height, and number of trailers were not enacted.
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18 PRovIDING ACCESS FOR LARGE TRUCKS Because a truck's trailer units account for most of its length, eliminating an overall length limit, it was argued, would not substantially increase the size of the vehicle. Grandfathered length limits: The act required states to continue to allow trailers of such dimensions as were actually and lawfully being operated before its passage [Section 411(b)
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Overview 19 within the area of its jurisdiction." In the regulations that implemented the STAA [U.S. Department of Transportation (DOT)
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20 PROVIDING ACCESS FOR LARGE TRUCKS caution in designating highways." Thus revisions of the width and access provisions were intended to improve the productivity of trucking operations but not at the expense of safety. The Tandem Truck Safety Act of 1984 also provided a mechanism for states to request the U.S.
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Overview 21 from which large commercial vehicles are generally excluded, to roads with lane widths less than 10 ft for 102-in.-wide vehicles, and to posted roads for which a safer alternative exists and (b) define "terminal" broadly as "any industrial, commercial, or job site location used for origination or termination" (Federal Register 1987, 299)
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22 PROVIDING ACCESS FOR LARGE TRUCKS Pennsylvania's access policies because it found that the state's policy of restricting access to service facilities to 0.2 mi from the National Network without considering the availability of these facilities was arbitrary and that the state's policy for approving terminal access required "an unreasonable amount of time pending review of route applications, and [was based on]
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Overview 23 newly authorized size in one state may have been legally operated in another state for several years. These differences among states explain much of the variation in state access policies.
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FIGURE 2-2 Legality of STAA vehicles before passage of 1982 STAA (TRB 1986, 26-28) : top, 48-ft tractorsemitrailers; middle, 65-ft twin trailer trucks; bottom, 102-in.-wide trucks.
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Overview 25 long tractor-semitrailers.] The legality of 102-in.-wide trucks was far less widespread; thus many states were required to pass legislation legalizing these vehicles subsequent to the 1982 act.
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ON DAKOTA is 57.4 63.5 00 0. HAWAII FIGURE 2-3 States with grandfathered semitrailer lengths greater than 48 ft on December 31, 1982 (Federal Register 1988a, 2,599)
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Overview 27 freight from rail or by generating new demand for truck transportation services. The diversion from rail that can be attributed to the size provisions of the 1982 STAA is likely to be small.
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28 PROVIDING ACCESS FOR LARGE TRUCKS are only one of several factors that drive industry locational decisions and distribution practices. The net effect of all of the factors just discussed is likely to be a smaller increase in truck traffic than would have been experienced with equipment of pre-STAA dimensions.
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Overview 29 of 48.5 ft, which, for all practical purposes, were considered equivalent to the 48-ft trailer dimension. Ten of these states have imposed overall length limits or wheelbase restrictions on, or require permits for, use of these vehicles (Motor Carrier Advisory Service, cited in Ponzani 1989,49)
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30 PROVIDING ACCESS FOR LARGE TRUCKS U.S. House of Representatives Report No.
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3 Current Access Policies and Practices T HE SURFACE TRANSPORTATION ASSISTANCE ACT (STAA) of 1982 provided that no state could deny reasonable access to STAA-authorized vehicles between the National Network and terminals and facilities for food, fuel, repair, and rest (i.e., service facilities)
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32 PROvIDING ACCESS FOR LARGE TRUCKS Determine procedures used by state and local governments to define and implement access policies, and Identify key elements of access policies and procedures that have enabled government and industry to reach agreement on the provision of reasonable access. The information in this chapter was obtained primarily through surveys of the highway and transportation departments of all 50 states and the District of Columbia, as well as state trucking associations (Appendix C)
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Policies and Practices 33 The Urban system, which includes 148,000 mi of high traffic volume arterials and collectors in urban areas. The Federal-Aid system is composed of about 20 percent of the country's highway mileage but carries 80 percent of all traffic (Table 3-1)
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34 PROVIDING ACCESS FOR LARGE TRUCKS approach that would have imposed few practical limits on their use (TRB 1986, 54)
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West Midwest East i L CflOflU0 Less than one-third - One-third to two-thirds Two-thirds to all AWfl,, FIGURE 3-1 Share of Federal-Aid primary mileage on the National Network.
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West Midwest East 1 /1 El I IScOcT L / co Cb f 0/ 4LA0 4 Tco-thdS to all FIGURE 3-2 Share of Federal-Aid primary mileage open to all STAA vehicles (including mileage on the National Network and state-designated networks)
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Policies and Practices 37 enactment of the 1982 STAA' and concerns about the ability of the highway systems to safely accommodate these vehicles. Typical restrictions include Bans on multitrailer trucks: In virtually all eastern states where twin trailer trucks were prohibited before passage of the 1982 STAA, few highways, apart from those already on the National Network, have been opened to twins.
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38 Piov1DING ACCESS FOR LARGE TRUCKS TABLE 3-3 STATES WITH WHEELBASE LIMITS Distance from Kingpin to State Rear Axle (ft) California 40 Idaho 39 Illinois 40 Iowa 40 Maine 38 Michigan 40.5 Minnesota 41 Tennessee 41 Wisconsin 41 Nom: The wheelbase distance is typically measured from the kingpin setting to the rear trailer axle or axles; although in Maine it is measured from the rear tractor axle instead of the kingpin.
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East Midwest West S wSCONS 'O4M0 OJtOAKOA Ic- .a'"° cOt 0 V W IIi aaf en with dilough-travot States with tirrled ttrrough-tcavoI snienqo for both twins and tractorsomwaitcrs FIGURE 3-3 States with limited (less than one-third of Federal-Aid primary)
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40 PROVIDING ACCESS FOR LARGE TRUCKS TABLE 3-4 PERCENTAGE OF FAP MILEAGE OPEN TO STAA VEHICLES BY VEHICLE CONFIGURATION Percentage Open Percentage Open to STAA Region to Twins Tractor-Semitrailers West 93 93 Midwest 91 91 East 35 48 U.S. Total 70 75 NcYrE: See Appendix C, Table C-i, for more details public roads.
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Policies and Practices 41 STAA-authorized truck size limits are too high given the physical characteristics of many roadways. Twins were the major concern in the East where they had not been common, but several states also noted that longer tractor-semitrailers are a problem.
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42 PROVIDING ACCESS FOR LARGE TRUCKS TABLE 3-5 PERCENTAGE OF NON-INTERSTATE FEDERAL-AID MILEAGE BY LANE WIDTH (Highway Statistics 1987 1988, 120-121) Region and Lane Width (ft)
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35 LU 30 25 LL 0 20 ul 15 OC 10 w C- 5 0 West Midwest East FIGURE 3-4 Federal-Aid (non-Interstate) mileage located in urban areas (Highway Statistics 1987 1988, 116)
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44 PROVIDING ACCESS FOR LARGE TRUCKS Summary Assessment Nationwide, approximately 70 percent of FAP system mileage is effectively open to all STAA vehicles. However, there are sharp regional differences.
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Policies and Practices 45 the states and the District of Columbia have defined the term in legislation or regulations. Wording that has been adopted by a number of states specifies that STAA vehicles can access all "points of loading and unloading." However, concerned that such a broad definition would result in STAA vehicles servicing businesses located in congested downtowns, 10 states have defined "terminal" in such a way as to specifically exclude retail stores and other businesses that are often located in congested business districts (Table 3-6)
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46 PROVIDING ACCESS FOR LARGE TRUCKS of a truck terminal, that is, a location with a minimum number of loading stations that is used primarily to transfer freight to smaller vehicles for local pickup and delivery. Judging from the responses to surveys of state trucking associations, the definitions of "terminal" have caused surprisingly few problems for users of STAA vehicles.
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Policies and Practices 47 the Midwest and the West, where many states have placed large portions of their highway systems on the National Network or on extensive state networks. For example, Illinois, Iowa, and Michigan have adopted a 5-mi limit from the National Network and other state-designated highways.
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TABLE 3-7 SUMMARY OF STATE ACCESS PROCEDURES Region Procedure West Midwest East Unlimited access (19) Colorado Arkansas Connecticut" Hawaii Indiana Maine" IdahoL Kansas Mississippi Montana Nebraska Rhode Island" Nevada Ohio Washington Oklahoma Wyoming South Dakota Texas Mileage limit (14)
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Route designation (20) State-designated network Arizona California Oregon Utah On request Other (6)
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50 PROVIDING ACCESS FOR LARGE TRUCKS TABLE 3-8 SUMMARY OF STATES WITH DISTANCE-BASED TERMINAL ACCESS POLICIES Percentage of Distance PAP Mileage Region and State Limit (mi) Open to STAA Vehicles West Alaska 25 23 New Mexico 20 >80 Midwest Illinois 5 92 Iowa 5 >80 Louisiana 3 100 Michigan 5 77 Missouri 10 45 Wisconsin 5 62 East Alabama 1 30 Kentucky 5 51 New Jerseyb 2 >90 North Carolina 3 60 South Carolina 3 29 West Virginia 2 25 Nom: Distance also applies for access to service facilities.
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Pblicies and Practices 51 TABLE 3-9 SUMMARY OF STATES WITH DISTANCE LIMITS FOR ACCESS TO SERWCE FACILITIES Percentage of Distance FAP Mileage Region and State Limit (mi) Open to STAA Vehicles West California' 0.5 >70 Oregon 0.5 >80 East Connecticut" 0.5 29 Florida" ito 3 18 Maine" 0.5 to 2 16 Maryland 1 30 New Jersey 27 >90 New York 1,500 ft 26 Pennsylvania 0.2 19 Rhode Island" 1 to 3 19 Vermont 0.5 24 Virginia 0.5 40 West Virginia 2 25 NOTE: In some states these distance limits may also be used for access to terminals located near the National Network.
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52 PROVIDING ACCESS FOR LARGE TRUCKS Implementation To determine how state access provisions are implemented, state highway officials and trucking associations were asked to describe how carriers are informed of access regulations, how conflicts are resolved, and how these regulations are enforced. Information and Conflict Resolution The following methods are used to provide information on access: Truckers' handbooks are published and distributed by many states to truckers as a reference to state laws and regulations pertaining to trucking, including access regulations.
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Policies and Practices 53 Motor carrier advisory groups, in response to the growing concern of the trucking industry about the complexities of access policies, provide a formal mechanism for the trucking industry to work with state officials to resolve access problems. Trucking associations in at least two states with a history of controversy over the extent of access provided -- Alabama and Pennsylvania -- reported noticeable improvements in the resolution of access problems after meetings of these groups.
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54 PROvIDING ACCESS FOR LARGE TRUCKS these states emphasize the adequacy of the roadway to accommodate STAA vehicles rather than the characteristics of the terminal itself. The procedures used by most states to provide access fall into two broad categories: (a)
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TABLE 3-10 ROAD MILEAGE CLASSIFIED BY FEDERAL-AID SYSTEM AND JURISDICTION, 1987 (Highway Statisitics 1987 1988, 113-115, 134-136) Federal-Aid System Other Non-Federal-Aid Jurisdiction Interstate Primary Secondary Urban Roads Total State 44,328 254,961 196,226 34,061 269,588 799,164 Local 0 2,690 201,449 113,849 2,544,203 2,862,191 Federal 0 469 654 69 211,479 212,671 Total 44,328 258,120 398,329 147,979 3,025,270 3,874,026
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56 PROVIDING ACCESS FOR LARGE TRUCKS TABLE 3-11 STATES CLASSIFIED BY LOCAL GOVERNMENT AUTHORITY TO DEFINE ACCESS Local Government Region Authority No. West Midwest East Hawaii Indiana Idaho Louisiana Montana Missouri Nevada Nebraska New Mexico North Dakota Utah Oklahoma Wisconsin State grants access 10 Alaska Arkansas with local input South Dakota Arizona Illinois California Iowa Colorado Kansas Oregon Michigan Washington Minnesota Wyoming Ohio Texas Connecticut Delaware Georgia Maryland Massachusetts Mississippi New Jersey North Caroliiia Vermont Florida Kentucky Maine New York Rhode Island South Carolina Virginia Alabama New Hampshire Pennsylvania Tennessee West Virginia State grants access 22 with no local involvement Local 18 governments have authority to define access on routes under their jurisdiction Extent of Local Involvement Responses to the interviews and surveys indicate that few local governments have developed access policies for STAA vehicles.
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Policies and Practices 57 Truck bans: Local governments reporting broad prohibitions on STAA vehicles or large trucks in general included Boston, which limits twins' activity during peak travel periods (rush hours) ; New York City, where twins are prohibited from all city streets and roads unless specially permitted; and Los Angeles, which is considering a peak-hour limitation on all truck travel, including that of twins and STAA tractor-semitrailers, on city streets.
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58 PROVIDING ACCESS FOR LARGE TRUCKS of identifying access routes and application procedures for access, which make compliance with local regulations both time consuming and administratively burdensome. In addition, many complained that local governments take more time to review access requests than do states and seldom specify the criteria used to conduct reviews, which causes carriers to question the ability of some local governments to make fair and technically sound judgments about access.
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Policies and Practices 59 reviews, and offering technical guidance and assistance in evaluating local access roads. SUMMARY OF FINDINGS State and local governments have responded to federal requirements that reasonable access be provided to STAA vehicles off the National Network by implementing a wide range of access policies.
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60 PRovIDING ACCESS FOR LARGE TRUCKS State Access Provisions Fifteen states allow STAA vehicles to travel virtually unrestricted on all public roads. The remaining 35 states and the District of Columbia have adopted a wide range of access policies.
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Policies and Practices 61 the permit holder, are usually identified in published lists. Although a few states use signs to mark terminal access roads, most do not because of the cost and impracticality of signing a large number of short road segments.
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62 PROVIDING ACCESS FOR LARGE TRUCKS practical restrictions are less severe in states in which access is provided in a timely manner and where state officials play a strong role in coordinating local access arrangements. Access policies that can be simply communicated and enforced.
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Policies and Practices 63 Hampshire, New Jersey, North Carolina, Pennsylvania, Rhode Island, South Carolina, Vermont, Virginia, and West Virginia -- and the District of Columbia. Although New Jersey did not specifically ban twins, its 55-ft truck length limit effectively barred the industry-standard 65-ft twin.
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STAA Vehicle Use and Productivity T HE TWIN TRAILER TRUCKS and larger tractor-semitrailers authorized by the 1982 STAA provide an opportunity for major productivity improvements in certain segments of the trucking industry and for subsequent reductions in freight transportation costs to some shippers. Carriers and shippers claim, however, that the restrictiveness of some truck access policies has created arbitrary limits on the use of STAA equipment that are insensitive to industry needs and have resulted in higher trucking costs.
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66 PROVIDING ACCESS FOR LARGE TRUCKS CHARACTERISTICS AND STRUCTURE OF THE TRUCKING INDUSTRY Trucking is a major and versatile component of the freight transportation system. During the past few decades the share of freight carried by truck has grown steadily as the highway system has been developed, automotive technologies have been improved, and shippers' needs have changed.
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STAA Vehicle Use and Productivity 67 *
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68 PROVIDING ACCESS FOR LARGE TRUCKS TABLE 4-1 COMBINATION TRUCKS AND MILES BY MAJOR USE, 1987 (Census Bureau 1984; Highway Statistics 1987 1988, 171)
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STAA Vehicle Use and Productivity 69 TABLE 4-2 COMBINATION TRUCKS AND MILES BY TYPE OF CARRIER AND RANGE OF OPERATION, 1987 (Census Bureau 1984; Highway Statistics 1987 1988, 171) Type of Carrier and Range of Opera- tion No.
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70 PROVIDING ACCESS FOR LARGE TRUCKS many as 100,000 Owner-Operators, who account for 10 to 15 percent of forhire truck travel (TRB 1987, 16; Census Bureau 1984,40, 96)
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30 25 STAA Vehicle Use and Productivity 71 0I I I I I I I 1980 1981 1982 1983 1984 1985 1986 1987 YEAR FIGURE 4-3 Freight movement by type of operation (Roberts and Fauth 1988, 342)
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72 PROVIDING ACCESS FOR LARGE TRUCKS TABLE 4-4 SHARE OF TL COMBINATION TRUCK MILEAGE BY TRAILER BODY TYPE (Census Bureau 1984) Share of Truck Miles Trailer Body Type (%)
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STAA Vehicle Use and Productivity 73 gional carriers that provide high service levels or serve special market niches (Hoffman 1988, 12-14)
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74 PROVIDING ACCESS FOR LARGE TRUCKS flexible services to shippers (Lane 1988, 11-14)
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STAA Vehicle Use and Productivity 75 trucking industry's conversion to STAA trucks since 1982. In the following subsections, a variety of sources, including trailer sales data and a series of motor carrier and shipper interviews conducted for this study (see Appendix D)
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76 PROVIDING ACCESS FOR LARGE TRUCKS Carrier Interviews Because trailer sales statistics do not provide information about the uses of the new STAA equipment, 20 for-hire carriers were selected for indepth interviews for this study. Included in this sample were 12 TL carriers and 8 LTL carriers that operate throughout the country.
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STAA Vehicle Use and Productivity 77 volumes of freight traffic; however, even these carriers foresaw continued conversion to from 60 to 100 percent twins. On the other hand, the LTL carriers reported only minor purchases of the longer and wider STAA semitrailers.
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78 PROVIDING ACCESS FOR LARGE TRUCKS plastic and aluminum articles, empty containers, textiles, general freight (mixed cargoes) , and household furniture and appliances.
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STAA Vehicle Use and Productivity 79 to carriers of low-density cargoes, because these trailers offer more cargo space than the previous standard 45-ft trailer, yet even carriers of predominantly heavy cargoes reported substantial conversion. For example, two midwestern carriers explained that by converting entirely to 48-ft trailers they maintain the flexibility to compete for both low- and high-density goods and avoid the logistic problems associated with tracking and balancing mixed (45-ft and 48-ft)
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80 PROVIDING ACCESS FOR LARGE TRUCKS tions in line-haul costs directly proportional to the additional volume capacity provided by the STAA semitrailers. However, because not all shippers have sufficiently light cargoes or large enough shipment sizes to take full advantage of the more spacious STAA semitrailers, more modest reductions were reported by some companies.
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STAA Vehicle Use and Productivity 81 had been largely prohibited, although these percentage increases still represent small traffic volumes. Nationwide vehicle counts indicate that twins accounted for between 5 and 6 percent of combination truck travel in 1986 (Table 4-9)
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82 PROVIDING ACCESS FOR LARGE TRUCKS Because of the small size of single 28-ft trailers, they are used most efficiently in the twin trailer configuration and are too inflexible for most TL operations. In comparison, the LTL carriers interviewed reported that twin trailer trucks are particularly well suited for their operations.
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STAA Vehicle Use and Productivity 83 nearly all reported using single pups for a significant share of pickups and deliveries. Carriers estimated that the reduction in freight handlings resulting from use of twins ranged from 10 to 35 percent, reflecting different carriers' circumstances and uses of twins.
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84 PROVIDING ACCESS FOR LARGE TRUCKS Growth in the use of twins has been concentrated within the LTL segment of the trucking industry. Because of the nature of their operations, LTL carriers can take advantage of the additional volume capacity of twins and the flexibility that dividing loads into smaller trailers allows to reduce line-haul mileage and terminal handling costs.
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STAA Vehicle Use and Productivity 85 In many states initial disputes between state and local governments and truck operators are being resolved as STAA vehicles become more familiar and accepted. Nevertheless, access regulations, where they are restrictive, can affect the optimal use of STAA equipment.
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86 PROvIDING ACCESS FOR LARGE TRUCKS ment in some states may become more stringent in the future. Although their companies have purchased STAA vehicles despite this uncertainty, they noted that this possibility has adversely affected decisions about purchasing equipment.
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STAA Vehicle Use and Productivity 87 Terminal definitions: Because some states define "terminal" so as to exclude many truckload destinations, TL carriers expressed concern that these definitions could become troublesome. TL carriers emphasized that, unlike LTL carriers, they do not maintain their own terminals for freight consolidation and breakbulk as defined in some state regulations; they normally depend on shipper and receiver facilities for direct loading and unloading.
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88 PROVIDING ACCESS FOR LARGE TRUCKS carriers estimated that as much as 30 percent of their shipments is adversely affected by access regulations that prevent them from dispatching twins to several key terminals. These carriers noted that because they structure their line-haul operations by terminal groupings, whereby vehicles are shuttled between several terminals to minimize travel time and vehicle miles, access limits at just one terminal can affect scheduling and equipment usage at several terminals.
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STAA Vehicle Use and Productivity 89 optimal conditions, all 13 percent of the additional cargo space provided by 48-ft semitrailers (compared with the previous industry-standard 45-ft semitrailer) would be used, and this mileage would be reduced by about 100 million miles per year (0.13 x 800 million miles)
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90 PROVIDING ACCESS FOR LARGE TRUCKS dard. On the other hand, the use of twin trailer trucks has been concentrated within the LTL segment of the industry.
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STAA Vehicle Use and Productivity 91 Because many carriers travel to a wide variety of locations that are often far from the National Network, short access distance limits may be inadequate for access to terminals and other destinations, unless such access is coupled with extensive through-travel networks. Also, because many carriers must be responsive to the changing daily needs of shippers, it may be impractical for them to apply for permission for access in advance.
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92 PROVIDING ACCESS FOR LARGE TRUCKS the intermediate terminal and loaded onto a tractor-semitrailer with other shipments to Atlanta. The space in the tractor-semitrailer bound for Columbia would then be filled with other shipments to Columbia.
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STAA Vehicle Use and Productivity 93 Office of Technology Assessment.
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5 Safety Accident Studies T HE SURFACE TRANSPORTATION ASSISTANCE ACT (STAA) of 1982 established safety as the primary criterion to guide the development of access policies for STAA vehicles on public roads within states.
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96 PROVIDING ACCESS FOR LARGE TRUCKS reviewed to identify information relevant to each of the preceding questions. Finally, the chapter concludes with a summary of the major findings about what is known, as well as what is not known, about the safety record of STAA vehicles.
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Safety 97 vehicles may have the same number of accident involvements, but if one travels twice the distance of the other, its accident rate (i.e., number of accident involvements divided by miles traveled) is half that of the other.
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98 PROVIDING ACCESS FOR LARGE TRUCKS h C-) 0 4 1979 1980 1981 1982 1983 1984 1985 1986 YEAR Passenger Car8 M Combination Vehicles FIGURE 5-1 Fatal accident involvement rates by vehicle type, 1979-1986 (NHTSA 1979-1986, Highway Statistics 1979-1986)
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Safety 99 trucks can travel at high speeds and the opportunity for accidents is far greater than on divided highways. Accident rates are also high on local roads, but these account for only a small fraction of total combination vehicle travel.
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100 PROVIDING ACCESS FOR LARGE TRUCKS reports, which usually do not distinguish between the various dimensions of interest (i.e., 48- versus 45-ft semitrailers or 102- versus 96-in, vehicle width) .5 Only 13 state highway and transportation departments,6 in the survey conducted for this study, reported that their accident records , distinguished between STAA and non-STAA vehicles, and the data are incomplete in six of these states.7 An additional six states indicated that these data would soon be available or could possibly be obtained by reprogramming existing data.
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Safety 101 (1980-1984) and the truck travel survey previously described, UMTRI analyzed fatal accident involvement rates for a variety of truck configura- tions and travel categories.
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TABLE 5-3 SUMMARY OF STUDIES EXAMINING ACCIDENT RATES BY TRUCK CONFIGURATION Study Principal Finding Involvement Rate Ratio: Twins to Tractor-Semitrailers (by VMT) Base Data and Method Campbell et at.
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TRB 1986 Twins are slightly overinvolved 0.98 to 1.12 Synthesis of prior studies for in truck crashes, but a pro- accident rates and indepen- jected 9 percent reduction in dent travel forecast truck travel from twins' greater capacity will offset any accident increase; no net Graf and Archuleta safety decrement Twins have higher accident in- 1.12 (rural roads) California data; 1979-1983 ac- 1985 volvement rates than tractor- 0.79 (urban roads)
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From page 110... ...
104 PROVIDING ACCESS FOR LARGE TRUCKS Jones 1988, 491) and that these differences were statistically significant.
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From page 111... ...
Safety 105 data derive, that is, large national LTL trucking firms conducting line- haul, general freight operations. The approach taken by the Jovanis study is modeled on an earlier effort by John Glennon to compare accident rates for twin trailer trucks and tractor-semitrailers by a matched pair analysis that controlled for differences in travel characteristics.
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From page 112... ...
106 PROVIDING ACCESS FOR LARGE TRUCKS characteristics, operation, and uses of twin trailer trucks and tractorsemitrailers are so different that a simple comparison of overall accident involvement rates would not provide an adequate explanation of their relative safety (Chira-Chavala and O'Day 1981, 12)
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From page 113... ...
Safety 107 characteristics, the study designs are such that the results cannot readily be extrapolated to a broad range of situations. For policy makers determining the extent to which STAA vehicles can operate safely off the National Network, the most important finding, on which the studies generally concur, is that vehicle configuration per se is less important in ascertaining the relative accident risk of these vehicles than are the types of roads on which and conditions under which they travel.
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From page 114... ...
Vehicle involvement in fatal and injury accidents 1976-1981 BMCS accident files for five-axle trucks carrying general freight in van trailers (ICC-authorized carriers) TABLE 5-4 SUMMARY OF STUDIES EXAMINING ACCIDENT SEVERITY RATES BY TRUCK CONFIGURATION Study Principal Finding Carsten 1987 No statistically significant difference in fatal or injury involvements for twins and tractor-semitrailers; lack of differences attributed to greater use of twins on divided highways and higher involvement of twins in singlevehicle crashes TRB 1986 No statistically significant difference between twins and tractor-semitrailers in fatal accident involvements; twins are involved in fewer injury accidents and differences are statistically significant Accident Severity Measure Vehicle involvement in fatal and injury accidents Base Data and Method 1980-1982 UMTRI fatal accident file; 1981-1984 NASS injury file; and 1982 Truck Inventory and Use Survey
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From page 115... ...
Fraction of accidents that result in fatalities and fraction of accidents that result in injury Incidence of a fatality to a car occupant in a car-truck accident BMCS 1977 accident data and 1977 travel data from the Truck Inventory and Use Survey; ICC-authorized carriers only 1973-1974 BMCS accident files for trucks > 13,000 lb and articulated trucks Vehicle involvement in fatal and California data; 1979-1983 casualty (i.e., fatal and injury) accident information and 1982 accidents - traffic counts Graf and Twins and tractor-semitrailers Archuleta have similar fatal accident 1985 .
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From page 116... ...
110 PROVIDING ACCESS FOR LARGE TRUCKS have a greater proportion of their accidents (i.e., 65 percent versus 51 percent) on rural roads.
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From page 117... ...
Safety 111 21)
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From page 118... ...
112 PROVIDING ACCESS FOR LARGE TRUCKS Accident Rates by 'ilype of Road The studies that have examined large combination vehicle accidents by road type generally agree on the types of roads that are associated with the highest accident involvements. As previously discussed, the UMTRI study examined fatal accident involvement rates for combination vehicles on three classes of highways and found that the highest rates were on major undivided highways and the lowest rates on divided highways (Campbell et al.
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From page 119... ...
Safety 113 Graf and Archuleta (1985) found that large-truck (i.e., tractor-semitrailer and twin trailer truck)
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From page 120... ...
114 PROWDING ACCESS FOR LARGE TRUCKS trailer) rather than in any particular vehicle dimension (e.g., longer trailer lengths, wider vehicles)
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From page 121... ...
Safety 115 lower total accident involvement rate than do tractor-semitrailers on local roads and an approximately equal accident involvement rate in intercity travel (Chira-Chavala and O'Day 1981, 73)
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From page 122... ...
116 PROVIDING ACCESS FOR LARGE TRUCKS Several of the studies reviewed for this report shed light on the comparative accident experience of large combination vehicles in urban and rural settings. The UMTRI study of fatal accident involvement rates found that fatal accident involvements for all combination vehicles were higher on urban than on rural divided highways, but that the reverse was true on undivided highways, which areclosest in character to truck access routes (Campbell et al.
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From page 123... ...
Safety 117 which results in higher injury rates. The studies do not consider what effect substituting STAA vehicles for combination vehicles of pre-STAA dimensions would have on these accident rates.
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From page 124... ...
118 PRovIDING ACCESS FOR LARGE TRUCKS The increase in combination vehicle width from 96 to 102 in. is clearly linked to the first and second features -- the adequacy of lane and shoulder width and shoulder type and bridge width.
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From page 125... ...
Safety 119 example, the largest benefit is achieved by the first foot of lane widening (Zegeer et al.
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From page 126... ...
120 PROVIDING ACCESS FOR LARGE TRUCKS The longer-wheelbase tractor-semitrailers are particularly susceptible to edge drops on the inside of horizontal curves because of the inward offtracking of the rear wheels of the truck (TRB 1987, 97)
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From page 127... ...
Safety 121 intersection improvements will reduce accidents is difficult because so many factors, such as sight distance, number of lanes, lane width, traffic volume, and traffic signalization, affect the safety of turns at intersections (TRB 1987, 95)
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From page 128... ...
122 PROVIDING ACCESS FOR LARGE TRUCKS and most have enough methodological flaws of one type or another to make it difficult to reach a definitive assessment. This finding also holds for studies that examined accident severity by vehicle configuration.
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From page 129... ...
Safety 123 NOTES Combination trucks include truck tractor-semitrailers, truck-full trailer combinations, multiple-trailer combinations (i.e., doubles and triples) , and bobtail truck tractors (i.e., tractors not pulling a trailer)
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From page 130... ...
124 PROVIDING ACCESS FOR LARGE TRUCKS Seven trips was the minimum number that could be used and still yield a sample of at least 100 million miles for each vehicle type, which had been determined a priori as an adequate travel volume. The studies were by Graf and Archuleta 1985, Chira-Chavala and O'Day 1981, and Glennon 1981.
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From page 131... ...
Safety 125 Chira-Chavala, T., D
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From page 132... ...
Highway Design and Accident Risk MAJOR FACTOR IN SELECTING APPROPRIATE ROADS for access is the adequacy of geometric design features of highways to accommodate the longer and wider STAA vehicles. Many roads on which access is sought were not built to the design standards of the Interstate system or other designated highways on the National Network.
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From page 133... ...
128 PROVIDING ACCESS FOR LARGE TRUCKS features that are likely to increase accident risk for STAA vehicles, given their particular handling and performance characteristics, relative to the vehicles they replace. IMPORTANT GEOMETRIC FEATURES The key geometric features that may pose problems for STAA vehicle travel can be grouped into three categories: Alignment features -- Sight distance for passing and stopping -- Slope and length of vertical grades -- Horizontal curvature Cross-sectional features -- Lane widths -- Shoulder widths -- Roadside design features Intersection, interchange, and ramp design elements -- Turns and sight distance at intersections -- Sight distance at railroad-highway grade crossings -- Interchange and ramp design Guidelines for each of these design elements have been established by the American Association of State Highway and Transportation Officials (AASHTO)
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From page 134... ...
Highway Design 129 lengths that range from 50 to 59.5 ft) and twin trailer lengths of up to 28 ft per trailer on the National Network and highways providing access to service facilities and terminals; overall length limits were abolished for vehicles traveling on these roads.
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From page 135... ...
130 PROVIDING ACCESS FOR LARGE TRUCKS RELATIONSHIP BETWEEN STAA VEHICLE OPERATING CHARACTERISTICS AND HIGHWAY GEOMETRIC FEATURES Although AASHTO's Policy on Geometric Design of Highways and Streets does not fully address the problems of designing highways to accommodate STAA vehicles, several studies have examined their impact on highway geometry. The adequacy of geometric design guides is affected by the characteristics and performance of STAA vehicles, including minimum turning radius, offtracking, length, width, braking, and weight-to-power ratio [Transportation Research Board (TRB)
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From page 136... ...
Highway Design 131 oncoming vehicle (Fancher 1986, 31)
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From page 137... ...
132 PRovIDING ACCESS FOR LARGE TRUCKS rent practices for marking no-passing zones on two-lane roads with high volumes of truck traffic are inadequate for any large combination vehicle should be kept in mind when these roads are evaluated for access. Vehicle width was found to have a less significant effect than vehicle length on passing behavior of passenger cars and thus on passing sight distance requirements.
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From page 138... ...
Highway Design 133 a relatively rare and random event, it is not generally appropriate to design for this situation. Stopping Minimum stopping sight distance is the distance required to stop a vehicle traveling at or near the design speed of a highway before it strikes a stationary object in its path.
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From page 139... ...
134 PROVIDING ACCESS FOR LARGE TRUCKS as the WB-50, STAA vehicles should not pose additional problems on grades on roads designed to current AASHTO design policies (Hall 1986, 160)
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From page 140... ...
Path of Fra Outside Tr Swept Pall Offtracklng Highway Design 135 FIGURE 6-1 Swept path width and offtracking of a truck negotiating a 90degree turn (Caltrans)
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From page 141... ...
136 PROVIDING ACCESS FOR LARGE TRUCKS TABLE 6-1 COMPARISON OF MAXIMUM SWEPT PATH WIDTHS OF DESIGN VEHICLES ON 90-DEGREE TURN, 60-FT RADIUS Kingpin-to-Center- of-Rear-Axle Dimension Maximum Swept Path Vehicle Configuration (ft)
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From page 142... ...
TABLE 6-2 MAXIMUM SWEPT PATH WIDTHS THROUGH ROADWAY SECTION CURVES Vehicle Configuration Turn Angle =30 Degrees and TR = 200 ft 250 ft 300 ft 400 ft Turn Angle = 60 Degrees and TR = 200 ft 250 ft 300 ft 400 ft 37-ft semitrailer, conventional cab (WB-50) 10.4 9.9 - 9.6 - 10.8 10 9.6 - 45-ft semitrailer, conventional cab 11.3 11 10.3 - 12 11.2 10.5 - STAA twin trailer, cab over engine 10.5 10 9.6 - 10.6 10 9.6 - STAA twin trailer, conventional cab 10.5 10 9.6 - 10.6 10 9.6 - 48-ft semitrailer, conventional cab 11.8 11.2 10.6 - 12.6 11.5 10.9 - 48-ft semitrailer, California cab 11.9 11.3 10.8 10.1 12.8 11.8 11.0 10.1 53-ft semitrailer, conventional cab 12.6 11.8 11.3 NA 13.6 12.5 11.7 NA 59-ft semitrailer, conventional cab 13.6 12.7 12.2 11.2 14.8 13.6 12.6 11.3 NOTE: Units are feet.
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From page 143... ...
138 PROVIDING ACCESS FOR LARGE TRUCKS old of large trucks, oversteering sharp horizontal curves at high speeds can increase the likelihood of rollover for both twin trailer trucks and tractor-semitrailers, a subject that is discussed at greater length in the subsection on interchange and ramp design. Under certain circumstances, the rear trailer of a twin trailer truck is more susceptible to rollover than the single trailer of a tractor-semitrailer unit.
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From page 144... ...
Highway Design 139 existing development are stringent controls. Ten-foot lanes are acceptable only on low-volume, low-speed roads; lane widths less than 10 ft do not provide adequate lateral separation between commercial vehicles.
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From page 145... ...
140 PROVIDING ACCESS FOR LARGE TRUCKS AASHTO recommends shoulder widths of between 10 and 12 ft for heavily traveled, high-speed highways and of between 6 and 8 ft on lowervolume roads (AASHTO 1984, 365)
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From page 146... ...
Highway Design 141 Intersection Design Intersections constructed to current AASHTO design guidelines pose at least two problems for STAA vehicles: (a) inadequate lane width for negotiating intersection turns without lane encroachment and (b)
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From page 147... ...
142 PROVIDING AccEss FOR LARGE TRUCKS 28 26 22 U WB-50 1982 STAA Semi 20 18 16 14 12 10 8 30 50 70 90 110 130 150 170 190 RADIUS (feet) FIGURE 6-2 Comparison of maximum offtracking characteristics of the WB-50 and the 48-ft STAA tractor-semitrailer (Hall 1986, 162)
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From page 148... ...
TABLE 6-3 MAXIMUM SWEPT PATH WIDTHS THROUGH INTERSECTION CURVES Vehicle Configuration Turn Angle = 60 Degrees and TR = 50 ft 60 ft Turn Angle = 90 Degrees and TR = 50 ft 60 ft Turn Angle = 120 Degrees and TR = 50 ft 60 ft 37-ft semitrailer, conventional cab (WB-50) 17 16 19 18 21 19 45-ft semitrailer, conventional cab 19.8 18.6 23 21.3 - 23 STAA twin trailer, cab over engine 16.8 156.8 18.8 17.0 20 18.0 STAA twin trailer, conventional cab 17 16 19.6 17.8 21 18.6 48-ft semitrailer, conventional cab 20.4 19.2 24.3 22 - 24.4 48-ft semitrailer, California cab 21.0 19.6 - 23 - - 53-ft semitrailer, conventional cab 21.7 20.9 26.8 24.8 30.8 27.8 59-ft semitrailer, conventional cab 24.6 23.2 30.2 27.9 35.6 32.0 NoTE: Units are feet.
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From page 149... ...
144 PROVIDING ACCESS FOR LARGE TRUCKS (including parking lanes) to accommodate a 48-ft tractor-semitrailer with a trailer wheelbase length of 41 ft (DeCabooter and Solberg 1989, 24)
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From page 150... ...
N1'L 1 IE -- 41 -- al I e.S PRRURC I?
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From page 151... ...
146 PROVIDING ACCESS FOR LARGE TRUCKS wheelbase STAA tractor-semitrailers are likely to present problems at many urban intersections, particularly those built to or below minimum AASHTO design requirements. However, the amount of upgrading required to accommodate STAA vehicles will vary as a function of the traffic volume, the composition of the traffic (i.e., the amount of STAA tractorsemitrailer traffic)
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From page 152... ...
Highway Design 147 tion characteristics)
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From page 153... ...
148 PROVIDING ACCESS FOR LARGE TRUCKS ramps (Ervin et al.
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From page 154... ...
Highway Design 149 FINDINGS A review of the literature on the relationship between STAA vehicle operating characteristics and roadway geometric design identified the key features of concern (Table 6-4)
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From page 155... ...
150 PROVIDING ACCESS FOR LARGE TRUCKS tion vehicle will spend significantly longer in the passing lane, particularly when passing an STAA twin trailer truck, than is provided by current practices for signing and marking no-passing zones. The additional time required to pass an STAA vehicle, however, is slight, and the requirements for passing sight distance include a generous amount of time for the passing driver to abort the passing maneuver; this allowance will remain unchanged whether the vehicle passed is a passenger car or an STAA vehicle.
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From page 156... ...
Highway Design 151 IMPLICATIONS FOR DEVELOPING ACCESS POLICIES Roads with restrictive geometry can be an impediment to providing access for STAA vehicles. Studies of STAA vehicle handling and performance relative to specific roadway geometric features provide the following guidance: STAA vehicles differ in their ability to handle different geometric features.
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From page 157... ...
152 PROVIDING ACCESS FOR LARGE TRUCKS Nine states have both identified needed improvements and modified their geometric design practices: California, Idaho, Illinois, Michigan, Minnesota, Oregon, Utah, Washington, and Wisconsin. Alabama, Arizona, Georgia, Kentucky, New Mexico, and Vermont have only identified needed geometric improvements; Florida, Iowa, Maine, Mississippi, Nebraska, Ohio, South Carolina, and South Dakota have only modified their geometric design standards.
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From page 158... ...
Highway Design 153 Heavy Trucks.
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From page 159... ...
7 Traffic Operations and Safety T RAFFIC CONGESTION HAS BECOME a major transporta-tion concern, particularly in the nation's metropolitan areas. Highway engineers must address not only the adequacy of highway geometry to accommodate STAA vehicle travel off the National Network but also the effects of these longer and wider vehicles on traffic operations.
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From page 160... ...
156 PROVIDING ACCESS FOR LARGE TRUCKS of the net impact of the introduction of STAA vehicles on traffic operations. MEASURING THE IMPACT OF HEAVY TRUCKS ON HIGHWAY CAPACITY To simplify the design of highways and intersections, traffic engineers express the traffic volume created by a traffic stream of different types of vehicles in terms of passenger-car equivalents (PCEs)
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From page 161... ...
Traffic Operations 157 2) , highway capacity is reduced by 9 percent to 2,545 vehicles per hour.2 If the same volume of truck traffic is introduced, but under the worst conditions (i.e., PCE = 12)
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From page 162... ...
158 PROVIDING ACCESS FOR LARGE TRUCKS traffic flow, they also increase accident risk. Several studies have documented that wide variations in vehicle speeds increase the probability of accidents (Solomon 1964, Cirillo 1968, and Hauer 1971)
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From page 163... ...
I- I 0 E .0 Traffic Operations 159 -- 1949 Study 1955 Study -- -- 1963 Study 1973 Study 1977 Study University of Michigan Transportation a Research Institute 1985 EMEMNE MMEMNAPPEN MENSHEME [NOMMMMME 10 20 30 40 50 60 70 80 GROSS WEIGHT, thousands of pounds (1000 lb = 0.454 Mg)
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From page 164... ...
160 PROVIDING ACCESS FOR LARGE TRUCKS trucks traveling straight through a level, signalized intersection based on vehicle acceleration rates and position in the queue (Molina et al.
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From page 165... ...
Traffic Operations 161 PCE; the further back the truck is in the queue, the longer the time it has to accelerate and the lower its PCE (Molina et al.
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From page 166... ...
162 PROVIDING ACCESS FOR LARGE TRUCKS impact, affecting passing behavior on two-lane roads and reducing traffic capacity and causing delays at intersections. Two-Lane Roads Large trucks have a more adverse impact on traffic flow on two-lane roads than on multilane highways because of their effect on passing behavior.
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From page 167... ...
Traffic Operations 163 6 mph slower or around a 65-ft truck traveling 8 mph slower (Troutbeck 1982, 326)
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From page 168... ...
164 PROVIDING ACCESS FOR LARGE TRUCKS problems of the longer-wheelbase tractor-semitrailers discussed in Chapter 6, is examined. Zegeer et al.
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From page 169... ...
Traffic Operations 165 signal on the cross street. This treatment allows truck drivers to take advantage of gaps as they occur.
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From page 170... ...
166 PROvIDING ACCESS FOR LARGE TRUCKS Other Vehicle-Related Factors Affecting 'J}affic Operations The TRB study committee for Twin Trailer Trucks conducted a literature review (TRB 1986, Appendix E) that examined the effects of STAA vehicles on several other important factors that affect traffic flow.
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From page 171... ...
Traffic Operations 167 ment of pre-STAA dimensions and thereby mitigated some of the adverse impact of truck travel on traffic operations. Although there will be degradations in traffic flow on roads with high traffic volumes and restrictive geometry, the net adverse affect on traffic operations of the slightly heavier, longer, and wider STAA vehicles is likely to be small.
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From page 172... ...
168 PROVIDING ACCESS FOR LARGE TRUCKS The magnitude of these adverse impacts depends on the volume of STAA traffic. Because the introduction of the larger STAA vehicles has resulted in a smaller increase in truck traffic than would have been experienced with equipment of pre-STAA dimensions, the net adverse impact on traffic operations of the slightly heavier and larger STAA vehicles is likely to be small.
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From page 173... ...
Traffic Operations 169 FHWA Federal Highway Administration NCHRP National Cooperative Highway Research Program TRB Transportation Research Board AASHTO.
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From page 174... ...
170 PROVIDING ACCESS FOR LARGE TRUCKS Troutbeck, R
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From page 175... ...
8 Highway Condition S TATE AND LOCAL HIGHWAY OFFICIALS are concerned that more widespread travel by STAA vehicles could accelerate the deterioration of transportation facilities, increase the cost of rehabilitation, and require more expensive new construction. Facilities of specific concern are pavements, bridges and culverts, and shoulders and highway appurtenances such as curbs, signs, and guardrails.
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From page 176... ...
172 PROVIDING ACCESS FOR LARGE TRUCKS (AASHTO's) method of analyzing pavement deterioration, and relevant research studies to determine what is known about the effect of these vehicles on the condition of highways, bridges, and highway appurtenances.
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From page 177... ...
Highway Condition 173 ment condition. A recent effort to extend the AASHTO pavement model to capture the features of today's heavy trucks that were not considered in the AASHO Road Test, such as increased tire pressures, tire type, multiple axles, and new suspension systems, concluded that the factors that have the most significant effect on pavement deterioration continue to be those considered in the initial road test, that is, the loads or weights on individual axles (J.
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From page 178... ...
1.5 Tandem axle 0 .
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From page 179... ...
Highway Condition 175 trucks are far more damaging to pavement surfaces than are passenger cars. For example, although a fully loaded five-axle tractor-semitrailer weighs the equivalent of about 20 automobiles, the truck causes the same damage as approximately 5,900 cars on an Interstate highway with flexible pavement (AASHTO 1986, Appendix D)
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From page 180... ...
176 PROVIDING AccEss FOR LARGE TRUCKS incorporate thicker pavement surfaces if the heavier loads are to be accommodated without reducing desired pavement life. Impacts of STAA Vehicles on Pavement Life: An Example The 1982 STAA authorized commerical vehicles of greater width and length than had been legal in some states before passage of the act (see Chapter 2)
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From page 181... ...
Highway Condition 177 TABLE 8-1 SIZE AND WEIGHT OF DESIGN VEHICLES Trailer Length Vehicle Tare Vehicle Payload Gross Vehicle (ft) Weight" (lb)
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From page 182... ...
178 PROVIDING ACCESS FOR LARGE TRUCKS loading, this effect should be offset to some extent by the simplifying assumption of full use of the added capacity of STAA vehicles. Damage Analysis Table 8-2 gives a summary of the incremental damage, expressed as load equivalencies, caused by the three STAA vehicles to flexible and rigid pavements.
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From page 183... ...
TABLE 8-2 AXLE LOAD ANALYSIS Axle 1 Axles 2 & 3 Axles 4 & 5 Adjustment Percentage Trailer Length Load Load Load Total Factor for Adjusted Change from (ft) (kips)
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From page 184... ...
180 PROVIDING ACCESS FOR LARGE TRUCKS Methodology To address this question, the effect of substituting different numbers of STAA vehicles in the traffic stream was investigated for a typical access highway. A rural principal arterial highway, with a volume and mix of traffic representative of this class of highway, was selected.5 A flexible pavement was assumed because a majority of major arterials fall into this category.
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From page 185... ...
Highway Condition 181 pavement rehabilitation costs were first established for the base case scenario using the methodology described in Appendix F Then the effects of substituting different volumes of STAA twin trailer and longer tractor-semitrailer truck traffic were analyzed for three likely alternatives.
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From page 186... ...
TABLE 8-4 IMPACTS OF INCREASED VOLUME OF STAA TRAFFIC ON PAVEMENT SERVICE LIFE FOR A RURAL ARTERIAL HIGHWAY Annual Percentage Pavement Percentage ESALs in Increase Service Reduction Design Desin over Lifec from Scenario ESALs Lane Base Case (years) Base Case Base case: 45-ft tractor-semitrailers 1,957 81,540 9.03 Case 1: Substitute twin trailer trucks for 10% of CTTd 2,166 90,260 10.7 8.16 9.6 Case 2: Substitute 48-ft tractor-semitrailers for 60% of CT!
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From page 187... ...
TABLE 8-5 IMPACTS OF INCREASED VOLUME OF STAA TRAFFIC ON PAVEMENT REHABILITATION COSTS FOR A RURAL ARTERIAL HIGHWAY Present Worth of Annual Percentage Rehabili- Percentage Design ESALs in Increase tation Increase ESALs" Desin over Base Costa over Base Scenario (000)
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From page 188... ...
184 PROVIDING ACCESS FOR LARGE TRUCKS dation. This assumption was tested in developing the model by examining a range of environmental conditions and the pavement serviceability loss associated with them.9 The results indicated that the incremental rehabilitation costs resulting from increased traffic loading increased only modestly as environmental wear intensified (Appendix F)
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From page 189... ...
Highway Condition 185 increase in pavement damage, represent a relatively small share of total combination vehicle travel. Moreover, as discussed in Chapters 4 and 5, the majntityiif travel by twins is on Interstate highways, particularly in those eastern states where access policies are most restrictive.
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From page 190... ...
186 PROVIDING ACCESS FOR LARGE TRUCKS trailer generates 0.749 ESAL at a cost of_6.2centsperESAL-milefor a Sübtituting the higher ESAL factor associated with STAA vehicles, 0.993, and applying the same ESAL-mile cost results in a total cost of $83.1 million -- a $20.8 million increase in total pavement rehabilitation costs if STAA vehicles are granted access on these roads. It could be argued that only a portion of these 1.35 billion vehicle-miles would be traveled off the National Network on access roads constructed to lower design standards.
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From page 191... ...
Highway Condition 187 At least one study (Ervin and Gillespie 1986) has been focused on the effects on pavement of increased travel by the longer STAA tractorsemitrailers.
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From page 192... ...
188 PROVIDING ACCESS FOR LARGE TRUCKS in Chapter 4) would increase pavement rehabilitation costs on these arterial highways from $8.1 million to $20.8 million.
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From page 193... ...
TABLE 8-6 NUMBERS OF BRIDGES ON FEDERAL-AID HIGHWAYS BY DESIGN LOAD (tabulations from bridge inventory data, U.S. Department of Transportation 1981, 111-75)
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From page 194... ...
190 PROvIDIIsJG ACCESS FOR LARGE TRUCKS with the same gross vehicle weights. For access routes the key questions are how do the forces induced in bridges by STAA vehicles compare with those induced by the vehicles they replace, and will the frequency of loading on these bridges change enough to increase fatigue damage?
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From page 195... ...
Highway Condition 191 of the tractor-semitrailers, the effect of the incremental stress is evident only for culverts with fill depths of approximately 2 ft or less, which is atypical of culverts on major highways (TRB 1986, 172-173)
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From page 196... ...
192 PROVIDING ACCESS FOR LARGE TRUCKS less than 35 to 45 mph, particularly on two-lane roads with sharp curves (see discussion in Chapter 6)
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From page 197... ...
Highway Condition 193 intersections is likely to involve, as a minimum, curb repair or relocation of curbs and street hardware and, as a maximum, intersection reconstruction. To the extent that offtracking of STAA tractor-semitrailers at intersections can be mitigated by regulating the trailer wheelbase as suggested in Chapter 6, the damage and related costs will be reduced.
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From page 198... ...
194 PROVIDING ACCESS FOR LARGE TRUCKS STAA vehicles on those access roads from which the major Users of STAA vehicles are now barred would range from $8.1 million to $20.8 million. The introduction of STAA vehicles is unlikely to have a serious adverse effect on the serviceability of properly designed bridges and culverts on access roads.
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From page 199... ...
Highway Condition 195 the terminal PSI value (i.e., expected remaining service life at the time the pavement needs rehabilitation) (Deacon 1988, 1 and AASH1'O 1986, I-il)
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From page 200... ...
196 PROVIDING ACCESS FOR LARGE TRUCKS FHWA Federal Highway Administration HRB Highway Research Board NCHRP National Cooperative Highway Research Program TRB Transportation Research Board U.S. DOT United States Department of Transportation AASHTO.
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From page 201... ...
Summary. Assessment T HIS CHAPTER CONTAINS THE major findings and recom-mendations for a national policy on reasonable access and the rationale for the recommended approach.
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From page 202... ...
198 PROVIDING ACCESS FOR LARGE TRUCKS (FHWA) in its notice of proposed rulemaking (Federal Register 1988, 53,009)
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From page 203... ...
Summary Assessment 199 urban systems have better geometries than primary highways. In addition, even if all FAP roads were open to STAA vehicles, access on other classes of highways would be required to reach terminals and service facilities that are not located on FAP highways.
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From page 204... ...
200 PROVIDING ACCESS FOR LARGE TRUCKS thus the potential exists for an even wider disparity in access policies at the local than at the state level. Given these findings, the committee concluded that the FHWA should require all states to adopt procedures based on safety and engineering considerations for assessing the adequacy of their highways to accommodate STAA vehicles.
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From page 205... ...
Summary Assessment 201 However, several critical operating characteristics of STAA vehicles are identified that, in conjunction with certain roadway conditions, could increase accident risk (Chapter 6)
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From page 206... ...
202 PROVIDING ACCESS FOR LARGE TRUCKS Review of Through- Travel Highways Because of the importance to safety of ensuring that large trucks travel on the best roads (i.e., those designed to the highest standards) , states that have limited miles of their FAP highways, or other roads built to equivalent standards, on the National Network or on state-designated networks should review other highways to determine if additional mileage can be opened to STAA vehicles.
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From page 207... ...
Summary Assessment 203 Access to Service Facilities States must ensure that carriers have adequate access to service facilities off the National Network and state-designated through-travel networks. Many states now allow STAA vehicles to travel a short distance, generally ranging from 1 to 3 mi, from the National Network to reach service facilities (see Chapter 3)
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From page 208... ...
204 PROVIDING ACCESS FOR LARGE TRUCKS Critical Vehicles and Dimensions for Regulation Inward offtracking is a problem for the longer-wheelbase STAA tractorsemitrailer. As discussed in Chapter 6 and Appendix E, the maneuverability of twin trailer trucks at speeds below 35 to 40mph is better than that of the pre-STAA tractor-semitrailers they replace.
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From page 209... ...
Summary Assessment 205 that of the 48-ft semitrailer with its rear trailer axle or axles in the farthest back position, and nearly equivalent to the pre-STAA 45-ft semitrailer, for a range of highway geometric conditions. The 48-ft semitrailer instead of the 45-ft semitrailer was selected as the standard vehicle for defining offtracking because the former is fast becoming the industry-standard semitrailer.
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From page 210... ...
206 PROVIDING ACCESS FOR LARGE TRUCKS Transportation (Caltrans) found that carriers of lightweight commodities (no denser than 11.9 lb/ft)
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From page 211... ...
Summary Assessment 207 state role in coordinating these evaluations can be critical to ensure a consistent and timely appraisal. States should take a leadership role in providing assistance to local governments on the technical and administrative aspects of devising access policies.
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From page 212... ...
208 PROVIDING ACCESS FOR LARGE TRUCKS Communication and Enforcement of Access Policies Many states have prepared maps, widely available to carriers and shippers, that show through-travel networks. These maps also frequently indicate general terminal access policies and any other restrictions on travel, such as offtracking regulations.
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From page 213... ...
Summary Assessment 209 STAA did not define "reasonable access," it also did not define "terminal." The survey of current state access policies and practices revealed that many states define "terminal" broadly as "point of loading or unloading"; only 10 states have a more specific definition (Chapter 3)
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From page 214... ...
210 PROVIDING ACCESS FOR LARGE TRUCKS those on through travel on residential streets or weight-posted roads or bridges. MONITORING THE PERFORMANCE OF STAA VEHICLES One of the difficulties of defining where access for STAA vehicles is appropriate, and where it is not, is the lack of information on the accident experience of these vehicles on different categories of roads.
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From page 215... ...
Summary Assessment 211 carriers, with the possible exception of the relatively small LTL carrier segment, need to travel broadly to many destinations off the National Network and thus cannot readily be confined to a network of the nation's "best" highways. The clear productivity benefits that result from the use of more efficient equipment create pressure to use this equipment on as many roads as possible, and the difficulty of enforcing restrictions on travel off the National Network when a majority of large trucks simply "go where they have to" encourages wider use of STAA vehicles.
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From page 216... ...
212 PROVIDING ACCESS FOR LARGE TRUCKS At high speeds, the critical vehicle is the twin trailer truck. Here, the problem is less that of offtracking than of vehicle rollover (see discussion in Chapter 6 and Appendix E)
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From page 217... ...
APPENDIX A Federal Legislation Mandating the Truck Access Study Surface Transportation and Uniform Relocation Assistance Act of 1987, Public Law 100-17, 100th Congress, April 2, 1987 (23 USC 101 et seq.)
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From page 218... ...
214 1974 (Public Law 93-643) , including permits for divisible loads and statutory provisions providing higher weights by formula, tolerance or statutory specification.
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From page 219... ...
215 refrain from issuing a final rule on this issue until after the Board has issued its report. The Department may proceed with its current efforts in this area including soliciting comments from interested parties through a notice of proposed rulemaking.
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From page 220... ...
APPENDIX B Sections of Highway Laws Relating to Truck Size Title IV Surface Transportation Assistance Act of 1982, as amended, Public Law 97-424, 97th Congress, January 6, 1983 (49 USC 2311-2313, 2316)
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From page 221... ...
218 twenty-eight and one-half feet in length, in a truck tractor-semitrailer-trailer combination if those trailers or semitrailers were actually and lawfully operating on December 1, 1982, within a sixty-five-foot overall length limit in any State. No State shall prohibit commercial motor vehicle combinations consisting of a truck tractor and two trailing units on any segment of the National System of Interstate and Defense Highways, and those classes of qualifying Federal-aid Primary System highways as designated by the Secretary pursuant to subsection (e)
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From page 222... ...
219 System highways, as designated by the Secretary, and (2) terminals, facilities for food, fuel, repairs, and rest, and points of loading and unloading for household goods carriers.
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From page 223... ...
220 Title I Tandem Truck Safety Act of 1984, Public Law 98-554, 98th Congress, October 30, 1984 (49 USC et seq.)
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From page 224... ...
221 The Secretary shall make such determination within a period of 120 days after the date of receipt of notification from a Governor under paragraph (1) of this subsection or the date on which the Secretary initiates action under this paragraph, as the case may be, with respect to such segment.
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From page 225... ...
222 subsection (a) of this section, the Secretary shall exempt such segment from such subsection for the purpose of allowing the State to impose a width limitation of less than 102 inches for vehicles (other than buses)
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From page 226... ...
223 (2) by inserting "(other than a segment exempted under subsection (e)
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From page 227... ...
APPENDIX C Quiestionnalres and Detailed Tables for Chapter 3 STATE SURVEY ON TRUCK ACCESS STATE DATE SURVEY RESPONDENT WHO MAY BE CONTACTED FOR CLARIFICATION OF RESPONSES TO THIS QUESTIONNAIRE: NAME - TITLE - ADDRESS TELEPHONE DEFINITIONS: STAA Vehicles -- vehicles of the dimensions specified in the Surface Transportation Assistance Act (STAA) of 1982 as amended, which include: Twin trailer truck combinations using trailers of up to 28 feet long; Truck tractor-semitrailer combinations using semitrailers up to 48 feet long; Trucks with widths of up to 102 inches.
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From page 228... ...
226 length limit on truck-tractors used in STAA vehicle combinations and from limiting the overall length of STAA vehicles using the National Network (see definition below) , and grandfathered longer semitrailers in those states which had accepted semitrailers in excess of 48 feet in length prior to December 1, 1982.
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From page 229... ...
227 If "Yes," please answer the following questions: Please indicate the mileage of these state-designated, non-equivalent routes. __________ miles Please describe the nature of the restrictions.
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From page 230... ...
228 Other. Please describe II.
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From page 231... ...
229 Briefly describe the rationale for your access policies as defined in II.B. NOTE: If you provide unrestricted access to all STAA vehicles, please skip to Question G
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From page 232... ...
230 E Do the state's access rules provide for access by requiring a special permit for operation on or by signing specific routes?
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From page 233... ...
231 Is there any charge for a permit or for route review? ____ Yes ____ No If "Yes," please specify the amount for: First application or review Renewal Since the 1982 STAA went into effect, how many applications for access have been received approved rejected are currently under review What are the, principal reasons for rejecting an application?
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From page 234... ...
232 Are these access provisions established by statute or by administrative procedure? Please check the box that applies.
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From page 235... ...
233 Maps showing access routes Lists of specific approved or restricted routes Special signs indicating approved or restricted routes Other. Please explain.
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From page 236... ...
234 If your answer is "No," please go on to Question C If "Yes," please describe what changes have been made.
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From page 237... ...
235 SURVEY OF STATE TRUCKING ASSOCIATIONS ON TRUCK ACCESS STATE ASSOCIATION NAME SURVEY RESPONDENT WHO MAY BE CONTACTED FOR CLARIFICATION OF RESPONSES TO THIS QUESTIONNAIRE: NAME - ADDRESS TELEPHONE DEFINITIONS: 1. STAA Vehicles -- vehicles of the dimensions specified in the Surface Transportation Assistance Act (STAA)
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From page 238... ...
236 STAA from the National Network to terminals and to facilities by checking below those categories that apply. (More than one category may apply.)
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From page 239... ...
237 application form, please enclose a copy.)
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From page 240... ...
238 The state sets access policies and makes the final decision on access, but local governments have input by reviewing access requests on local routes over which they have jurisdiction. Local governments have authority to veto access on local routes over which they have jurisdiction Local governments have independent authority both to define and implement access policies on routes over which they have jurisdiction Other.
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From page 241... ...
239 Strict (i.e., enforcement authorities issue more than 10 citations per month for access violations) Moderate (i.e., enforcement authorities issue between ito 10 citations per month for access violations)
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From page 242... ...
240 What are the main access problems? Please number in order of priority (e.g., 1 = most.
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From page 243... ...
241 In what ways do you think state access provisions should be revised to ease the current restrictions? Has there been any movement or trend towards resolution of access problems in the state?
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From page 244... ...
TABLE C-i THROUGH-TRAVEL MILEAGE ON THE FEDERAL-AID PRIMARY SYSTEM (Highway Statistics 1987 1988, 132, and TRB survey of state highway and transportation departments) National Additional Mileage Network State-Designated Percentage of All Open to STAA Percentage of All Region and State Mileage Mileage Primary Mileage Tractor-Semitrailers Primary Mileage East Alabama Connecticut Delaware District of Columbia Florida Georgia Kentucky Maine Maryland Massachusetts Mississippi New Hampshire New Jersey New York North Carolina Pennsylvania Rhode Island South Carolina Tennessee Vermont Virginia West Virginia Regional subtotal Midwest Arkansas 1,730 500 30 >2,500b >70 470 - 29 1,140 100 210 - 40 - 40 20 - 9 - 9 1,670 - 18 >5,000d >70 1,770 350 16 700k 25 2,690 - 51 - 51 380 - 16 1,9509 100 780 - 30 - 30 650 - 23 - 23 6,410 - 100 - 100 280 - 20 >900k >80 510 - 27 >1,000' >90 1,980 250' 26 - 26 3,210 - 60 - 60 2,120 >500' 19 - 19 90 - 19 380 100 1,930 - 29 - 29 2,590 - 36 - 36 350 - 24 - 24 2,590 10' 40 - 40 720 - 25 - 25 33,150 1,610 35 13,570 48 5,750 - S 100 - 100
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From page 245... ...
Illinois 6,700 3,830k 92 - 92 Indiana 6,060 - 100 - 100 Iowa 7,680 >500k >80 - >80 Kansas 8,930 - 100 - 100 Louisiana 3,860 - 100 - 100 Michigan 5,470 960k 77 - 77 Minnesota 4,830 2,500k >80 - >80 Missouri 3,580 - 45 - 45 Nebraska 7,670 - 100 - 100 North Dakota 2,250 4,010' 100 - 100 Ohio 8,140 - 100 - 100 Oklahoma 6,240 - 100 - 100 South Dakota 6,470 - 100 - - 100 Texas 19,920 - 100 - 100 Wisconsin 3,720 2,500k 62 - 62 Regional subtotal 107,270 14,300 91 0 91 West Alaska 490 - 23 - 23 Arizona 2,510 >1,500'" >80 - >80 California 4,190 >5,000" >70 - >70 Colorado 5,240 - 100 - 100 Hawaii 540 - 100 - 100 Idaho 1,920 1,270° 100 - 100 Montana 6,540 - 100 - 100 Nevada 2,390 - 100 - 100 New Mexico 3,200 800" >80 - >80 Oregon 3,680 >500 >70 - >70 Utah 1,890 1,620'" 100 - 100 Washington 5,790 - 100 - 100 Wyoming 3,910 - 100 - 100 Regional subtotal 42,290 10,690 93 - 0 93 U.S. total 182,710 26,600 70 13,570 75 (continued)
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From page 246... ...
TABLE C-i THROUGH-TRAVEL MILEAGE ON THE FEDERAL-AID PRIMARY SYSTEM (Highway Statistics 1987 1988, 132, and TRB survey of state highway and transportation departments) (continued)
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From page 247... ...
TABLE C-2 ACCESS PROVISIONS FOR TWIN TRAILER TRUCKS (TRB survey of state highway and transportation departments) Percentage of FederalAid Primary Mileage Region and State Access Distance Limit Other Access Provisions Open to Twinst East Alabama 1 mi Additional 500-mi state-designated 30 network open to twins; 1-mi limit applies on National Network and state-designated network; special requests from local governments for access beyond 1-mi limit Connecticut 0.5 mi Special requests for access beyond 29 0.5-mi limit Delaware - Special requests for access 40 District of - Special requests for access 9 Columbia Florida' 1 mi on two-lane rural roads and on Special requests for access beyond 18 urban roads with 12-ft lanes; 3 mi distance limits on four-lane rural roads Georgian - Additional 350-mi state-designated 16 network open to twins; access provided on posted routes or by special request; access to services provided at posted interchanges Kentucky 5 mi - 51 Mainec 0.5 mi on four-lane urban roads; 2 Special requests for access beyond 16 mi on rural roads distance limits Maryland 1 mi to service facilities Shortest practical route to terminals 30
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From page 248... ...
TABLE C-2 ACCESS PROVISIONS FOR TWIN TRAILER TRUCKS (TRB survey of state highway and transportation departments) (continued)
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From page 249... ...
100 92 Unlimited Additional 3,800-mi state-designated network open to twins; 5-mi limit applies on both National Network and state-designated network Unlimited Additional state-designated network (>500 mi) open to twins; 5-mi limit applies on Interstate highways only; however, access extends to all roads within the following distances of cities: City Population Distance (mi)
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From page 250... ...
TABLE C-2 ACCESS PROVISIONS FOR TWIN TRAILER TRUCKS (TRB survey of state highway and transportation departments) (continued)
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From page 251... ...
Idaho - Unlimited, although restrictions 100 apply on some highways for vehicles exceeding 75 ft in overall length Montana - Unlimited 100 Nevada - Unlimited 100 New Mexico 20 mi Additional 800-mi state-designated >70 network open to twins; 20-mi limit applies on National Network and state-designated network Oregond 0.5 mi Access distance limit applies on >70 National Network; additional access provided by 500-mi state- designated network; special requests from local governments for access from this network Utah - Unlimited. 100 Washington' - Unlimited 100 Wyoming" - Unlimited 100 NorE: Provisions in some states may have changed since the survey (June 1988)
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From page 252... ...
TABLE C-3 ACCESS PROVISIONS FOR STAA TRACTOR-SEMITRAILERS (TRB survey of state highway and transportation departments) Percentage of FederalAid Mileage Open to STAA Tractor- Region and State Access Distance Limit Other Access Provisions Semitrailersb East Alabamac - 96-in.-wide semitrailers up to 50 ft >70 long are unrestricted; 50-ft by 102- in.
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From page 253... ...
Georgiad - 48-ft by 102-in. semitrailers are al- 25 lowed on virtually all highways with 12-ft lanes, unless the overall length of the vehicle exceeds 60 ft; a 1,000-mi state-designated net- work is open to vehicles up to 67.5 ft long; access to terminals is pro- vided on posted routes or by spe- cial request; access to services is provided at posted interchanges Kentucky 5 mi - 51 Maine - 48-ft by 102-in.
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From page 254... ...
TABLE C-3 ACCESS PROVISIONS FOR STAA TRACTOR-SEMITRAILERS (TRB survey of state highway and transportation departments) (continued)
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From page 255... ...
Virginia West Virginiac Midwest Arkansas IlljnOiSc Ui w Indiana lowac 0.5 mi Special requests for access beyond 0.5-mi limit 2 mi 48-ft by 96-in.-wide semitrailers are allowed on most highways, unless vehicle length exceeds 60 ft; 102in. trucks and vehicles longer than 60 ft are restricted to the National Network plus 2 mi for access Unlimited 5 mi 5-mi limit applies on National Network and 3,800-mi statedesignated network; a 40-ft wheelbase limit (measured from the kingpin to the center of the rearmost trailer axle)
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From page 256... ...
TABLE C-3 ACCESS PROVISIONS FOR STAA TRACTOR-SEMITRAILERS (TRB survey of state highway and transportation departments) (continued)
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From page 257... ...
Texasc Wisconsin West Alaska Arizonac California'' - Unlimited 5 mi 5-mi limit applies on National Network and 2,500-mi statedesignated network; 102-in. vehicles are unrestricted; a 41-ft wheelbase limit (measured from the kingpin to the center of the rearmost trailer axle or group of axles)
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From page 258... ...
TABLE C-3 ACCESS PROVISIONS FOR STAA TRACTOR-SEMITRAILERS (TRB survey of state highway and transportation departments) (continued)
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From page 259... ...
Washington - Unlimited 100 Wyoming - Unlimited 100 Nore: Provisions in some states may have changed since survey (June 1988)
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From page 260... ...
APPENDIX D Carrier and Shipper Surveys INTERVIEW GUIDE FOR TRUCKLOAD FOR-HIRE CARRIERS TRUCK ACCESS STUDY NAME OF PERSON INTERVIEWED TITLE COMPANY DATE DEFINITIONS: 1. STAA Vehicles -- vehicles of the dimensions specified in the Surface Transportation Assistance Act (STAA)
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From page 262... ...
261 E General characteristics of truck trips Total number of truckload trips in 1987 (or most recent year avail- able)
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From page 263... ...
G. What are or would be the relative advantages and disadvantages of using twins for your operations?
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From page 264... ...
263 unloading would be located within this mileage restriction? If this access restriction were relaxed to 5 road miles from the National Network, then what percentage of your points of loading and unloading would be located within this mileage restriction?
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From page 265... ...
264 III. IMPACTS OF STAA TRUCK ACCESS RESTRICTIONS What percent of your truckload trips, if any, would you estimate are adversely affected by policies of state and local governments restricting access to points of loading and unloading?
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From page 266... ...
265 Ask for specific examples of where carrier has had to apply for an access permit, obtain a route designation, or negotiate with a state or local government to obtain access to points of loading or unloading where the process has worked? where it has not worked?
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From page 267... ...
266 In your opinion, what information should states provide to the trucking industry, and in what form, concerning their access policies? ________________________________________ In what ways do you think truck access provisions should be revised to ease the àurrent restrictions?
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From page 268... ...
267 Network (see definition below) , and grandfathered longer semitrailers in those states which had accepted semitrailers in excess of 48 feet in length prior to December 1, 1982.
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From page 270... ...
269 Reduce rehandling of shipments at terminals (i.e., breakbulk on pups) Provide greater operating flexibility (e.g., use of pups for local delivery etc.)
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From page 271... ...
270 Follow-up if answer is "Yes" [i.e., see if they can send annual accident data by truck type and travel (exposure) data for these same vehicle types]
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From page 272... ...
271 2. Would a "one-stop" process at the State level for coordinating local government review of access route requests be desirable?
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From page 273... ...
272 Provide your worst case example of an access problem and its costs In your opinion, what information should states provide to the trucking industry, and in what form, concerning their access policies? In what ways do you think truck access provisions should be revised to ease the current restrictions?
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From page 274... ...
273 Twin trailer truck combinations using trailers of up to 28 feet long; Truck tractor-semitrailer combinations using semitrailers up to 48 feet long; Trucks with widths of up to 102 inches. Other specialized equipment as defined.
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From page 275... ...
274 Annual miles travelled in 1987 (or most recent year available) total truckload miles full miles empty miles For shippers contracting with for-hire carriers, ask the following questions about .the shipper's relationship.
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From page 276... ...
275 Average distance per truck shipment (i.e., average length oftruck shipment) (miles)
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From page 277... ...
What are or would be the relative advantages and disadvantages of using twins for your operations? (ask only if they use semis)
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From page 278... ...
277 c. If this access restriction were relaxed to 10 miles from the National Network, then what percentage of your points of loading and unloading would be located within this mileage restriction?
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From page 279... ...
% Cannot get from or to required destination using STAA equipment and so must use non-STAA equipment % Can get from or to destination, but must make lengthy detours % No problem with access NOTE: Ask for examples of each type of access problem Are there any particular regions of the country where you do business that have greater problems with access than others? If so, please specify those regions (or states)
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From page 280... ...
279 Example of process working Example of process not working Can you identify the costs of restrictive access provisions? (Try to obtain specific examples with cost estimates and then ask how representative these costs are of the entire operation)
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From page 281... ...
In what ways do you think truck access provisions should be revised to ease the current restrictions? If these changes were made, what percentage of your shipments would be made using STAA vehicles?
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From page 282... ...
APPENDIX E Off tracking One of the key issues in determining appropriate highways for access is the extent to which existing highways, particularly those with restrictive geometry, can safely accommodate STAA vehicles. Of particular concern is the maneuverability of the STAA vehicles relative to each other, to the vehicles they replace, and to the design vehicles for which existing highways were constructed.
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From page 283... ...
282 with long wheelbases. From the perspective of highway design, the relevant measure of offtracking is the swept path width, which is the amount of roadway width the vehicle takes up in negotiating the turn (i.e., the amount of offtracking plus the width of the vehicle)
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From page 284... ...
283 most severe (intersections built to lower design standards) trucks are traveling at slow speeds, so the accident consequences are less critical.
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From page 285... ...
BE of of le FIGURE E-1 Offtracking computer model inputs, roadway characteristics: turn angle and turn radius. Kingpin 5th Wheel Offset Tractor Wheelbase I I I Kingpin to Center of Rear Axle or Axles FIGURE E-2 Offtracking computer model inputs, vehicle characteristics: tractor wheelbase, 5th wheel offset, kingpin to center of rear axle (most important)
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From page 286... ...
TABLE E-1 DESIGN VEHICLE DIMENSIONS FOR OFFTRACKING COMPUTER MODEL ANALYSIS Vehicle Dimension (ft) Configuration A B C D E F G H T 37-ft semitrailer, conventional cab 3 18 0 30.0 4.0 - - - 55 (WB-50)
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From page 287... ...
286 many existing intersections, and the second with a 45-ft trailer -- two STAA twin trailer trucks, and four STAA tractor-semitrailers of trailer lengths ranging from 48 to 59 ft (Table E-1)
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From page 288... ...
BC - -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- KEY BC = Beginning of Curve MOT =MaxirnurnOffiracking EC End of Curve \MOT TRUCK OFFTRACKING \ Tractor-Semitrailer with Tractor A GEOM Y Wheelbase Length 0120 ft. Trailer Wheelbase Length 0138 ft.
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From page 289... ...
180 150 - - I 0o 0 0 - u 0 ) 0 0 ( 0 cJ c'J ,- CO - II II II II II II II I, cc cc cc cc cc cc I- - TR = Turn Radius (ft)
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From page 290... ...
180 150 120 H H CO R=TurnRadius(ft) 30 0 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 MAXIMUM OFFTRACKING (feet)
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From page 291... ...
1 150 120 0 it)
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From page 292... ...
180 150 120 V Ui -J c 90 z z - I- 60 30 C o ol 01 Cl) C•.J C'i .- (I OD II II II II It II TR Turn Radius ft)
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From page 295... ...
180 150 120 0 90 60 li II ) i Ni Ci 7 II I cc I I I I I 30 TR = Turn Radius (ft)
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From page 296... ...
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 15 17 15 1 U ZI ZZ ZJ 44 40 40 ef o .'.' MAXIMUM OFFTRACKING (feet) FIGURE E-11 Maximum offtracking for 59-ft tractor-semitrailer (conventional cab)
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From page 297... ...
60 75 15 0 0 - - 0 0 CD Cr ft If II I- F- I- R:Turn Radius () 4.0 J :3.5 4 4.5 MAXIMUM OFFTRACKING (feet)
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From page 298... ...
297 semitrailer needs 12.6 ft. Finally, compare these pavement requirements with the actual lane and shoulder width available.7 Idaho has also developed graphic representations of the maximum offtracking of several design vehicles for a range of truck turning radii and provided accompanying design guidelines for minimum pavement widths.
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From page 299... ...
B 2 909 0 .n STAA TRUCK SEMITRAILER WHEEL TRACKS SCALE IN FEET 0 50 100 150 15.1-I_I- FIGURE •E-12 Intersection turning template for STAA 48-ft tractor- semitrailer, 50-ft turn radius (Caltrans)
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From page 300... ...
2 4b0 . 900 0 All i STAA TRUCK SEMITRAILER WHEEL TRACKS SCALE IN FEET 0 50 100 150 now FIGURE E-13 Intersection turning template for STAA 48-ft tractorsemitrailer, 60-ft turn radius (Caltrans)
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From page 301... ...
300 NOTES Technically, offtracking is defined as the lateral deviation of the path of the center of the steering axle from the path of the center of the last axle. Swept path width is the offtracking amount plus half of the width of the steering axle (i.e., from the center of the axle to the outside edge)
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From page 302... ...
301 DeCabooter, P
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From page 303... ...
APPENDIX F Pavement Rehabilitation Cost Model This appendix provides a brief description of the pavement rehabilitation cost model used in Chapter 8 to estimate the impact on pavement service life and rehabilitation costs of an increase in axle loads on a typical arterial access highway.' The model provides cost estimates for flexible and rigid pavement, but only the former is described here because the-example in Chapter 8 is based on a flexible pavement. ELEMENTS OF THE MODEL The model incorporates the overlay design procedures recommended by AASHTO (AASHTO 1986)
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From page 304... ...
304 TABLE F-i PAVEMENT REHABILITATION COST MODEL ASSUMPTIONS AND INPUTS Assumption Value Design Assumptions Minimum overlay thickness 2 in. Terminal serviceability 2.5 PSI Rehabilitation interval 12 year Restore pavement condition to 4.2 PSI Present serviceability index 3.4 Structural number 4 Subgrade modulus of resilience 6,250 psi Annual design-lane ESALs 81,550 to 100,100 Cost Assumptions Fixed costs $90,000/mi Variable costs $15,000/in./mi' Number of lanes 2 Lane width 12 ft Shoulder width 4 ft NOTE: PSI = Present Serviceability Index psi = pounds per square inch This cost assumes in-place costs of asphalt concrete of $25 to $30 per ton Pavement rehabilitation is a recurring activity the costs of which can be considered periodic future lump-sum expenditures.
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From page 305... ...
0 .8 .6 Uj .4 .2 0 0 1 2 3 4 ANNUAL DESIGN-LANE ESALS (Millions) FIGURE F-i Sensitivity of marginal unit cost of pavement rehabilitation to level of pavement loading -- typical flexible pavement.
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From page 306... ...
306 Marginal rehabilitation costs are relatively insensitive to the effects of other pavement design variables, such as structural number and subgrade modulus of resilience. ENVIRONMENTAL EFFECTS The effect of environmental factors was also considered in developing the cost model.
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From page 307... ...
307 ment rehabilitation costs, the environmental component was varied so that environmental serviceability loss at the end of the 12-year cycle varied from zero, or no environmental degradation, to one, or a 67 percent loss of total pavement serviceability attributable to environmental factors. As Figure F-3 shows, the incremental rehabilitation costs attributable to heavier axle loads are not sensitive to environmental factors except under the most severe conditions.
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From page 308... ...
APPENDIX G Dissenting Statement I am unable to concur in the report of the Committee without these qualifications. My reasons are these: The report does not give due regard to overall safety.
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From page 309... ...
310 That is not reasonable. The lumping together leads states to deny access routes to safe vehicles.
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From page 310... ...
Study Committee Biographical Information ROLAND A OUELLETTE, Chairman, is President of the Eno Foundation for Transportation.
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From page 311... ...
312 Department of Transportation, she has held several positions, including Chief of Safety Project Evaluation, Senior Policy Specialist, and Assistant to the Director of the Division of Highways. Currently, she is Chairperson of the Illinois Motor Carrier Advisory Committee and member of the Congressional Office of Technology Assessment's Advisory Panel on Motor Carrier and Airline Safety.
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From page 312... ...
313 Committee of the American Trucking Associations. He serves on TRB's Committee on Urban Goods Movement and is a newly appointed member of TRB's Executive Committee.
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From page 313... ...
314 Vtr 'CLEVE HOLMES is a Lieutenant and Assistant Commander of the Truck Enforcement Division of the Maryland State Police, responsible for enforcing'federal and state truck safety regulations and laws. He received a bachelor's degree in administration of justice from American University.
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From page 314... ...
315 currently Chairman of the Design Management Committee and a member of the Technical Steering Committee on Vehicle Weights of the Roads and Transportation Association of Canada.
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From page 315... ...
316 bachelor's degree from Virginia Polytechnic Institute and State University and a master's degree in engineering from the University of Kentucky. Between 1979 and 1986, he served as Director of Traffic and Safety for Goodell-Grivas, Inc., and later as Vice President.
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From page 316... ...
1989 TRANSPORTATION RESEARCH BOARD EXECUTIVE COMMITTEE Chairman: Louis J Gambaccini, General Manager, Southeastern Pennsylvania Transportation Authority (SEPTA)
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From page 317... ...
The Transportation Research Board is a unit of the National ResearciCouncil, which serves the National Academy of Sciences and the National Academy of Engineering. The Board's purpose is to stimulate research concerning the nature and performance of transportation systems, to disseminate the information produced by the research, and to encourage the application of appropriate research findings.
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From page 318... ...
f tk .'.
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Key Terms
This material may be derived from roughly machine-read images, and so is provided only to facilitate research.
More
information on Chapter Skim is available.