Managing Selected Transportation Assets: Signals, Lighting, Signs, Pavement Markings, Culverts, and Sidewalks (2007)

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49 OVERVIEW Signs help inform, guide, and regulate traffic, including vehicular traffic, pedestrians, and cyclists. Good signage must communicate its information clearly and with sufficient lead time to transport system users in daytime and nighttime and in variable weather conditions. Signs must be visible to drivers in vehicles of different characteristics regarding head- lights and heights of drivers’ eyes above the road surface. Pedestrian and vehicular signs must be legible to different population groups, such as the elderly. The importance of good signage to public safety, particularly in nighttime, is well recognized in the literature. The percentage of total high- way fatalities that occurs at night is more than double the percentage of travel during this period, with inadequate or poorly maintained signage often cited as a contributing fac- tor (How Retroreflectivity . . . 2005). Additional facts and statistics regarding nighttime versus daytime crash trends, driver visibility, and the role of traffic signage are also pro- vided by the FHWA (“Nighttime Visibility Facts . . .” n.d.; “Driver Night Visibility Needs” n.d.). Agencies participating in the survey that was conducted for this study were asked to rank in order of importance the transportation objectives that are served by roadway signage. The composite results across all responding agencies are given in Table 11. Meeting these objectives calls upon agencies to observe standards, technical recommendations, and guidelines from a variety of sources. Figures 37 and 38 present agencies’ judg- ments of those sources of guidance that are the important drivers of engineering and management decisions regarding roadway signs. These results are shown for two key aspects of asset management: new construction and installation, and maintenance and rehabilitation, respectively. The importance of national standards, and especially indi- vidual agency policies, standards, guidelines, and proce- dures, is evident in these results. The international definition and measurement standard for retroreflection is published by the International Commission on Illumination (Commission Internationale de L’Eclairage) (Retroreflection . . . 2001). The U.S. national standard for signs is the MUTCD, supple- mented by further U.S.DOT/FHWA guidelines on sign retroreflectivity and sign management as discussed here. There are also AASHTO guidelines for pedestrian-related signs (A Policy on Geometric Design . . . 2004), specifications for sign structural supports (Standard Specifications for Structural Supports . . . 2001), and guidelines on roadside structures (Roadside Design Guide 2002). In addition, many agencies have their own manuals and guidelines for traffic control devices. These supporting or supplementary docu- ments by U.S. agencies must conform substantially to the MUTCD, as noted in chapter two. The literature review has identified several examples of individual agency guidelines for signs from all levels of government: • State DOTs [e.g., the Delaware DOT Traffic Control Manual (2000), Kansas DOT Special Provision . . . (1990), Maryland SHA Standard Sign Book; MnDOT Traffic Engineering Qualified Products . . . ; South Dakota DOT Materials for Highway Signs . . . ; and Texas DOT Signs and Markings Manual (2006). Agencies also incor- porate signage guidelines in their intersection design guides [e.g., University of Florida for the Florida DOT, Florida Intersection Design Guide . . . (2002)]. • Provincial transportation agencies (e.g., Filice 2003; Specifications for Standard Highway Sign Materials . . . 2004). • Local agency and tribal technical assistance (e.g., Mon- tebello and Schroeder 2000; Andrie et al. 2001). • City government, Lincoln, Nebraska (Standard Specifi- cations . . . 2006). Although these guidelines differ in scope and detail, in general they include information such as the following: • General discussion of the functions and types of signs. • Applicable standards, test procedures, and related documents. • Explanations and characteristics of different grades and colors of sign sheeting, including retroreflective properties. • Sheeting requirements by sign type, which may include tables of minimum retroreflectivity requirements and color specifications (chromaticity requirements). • Sign substrate types and requirements. • Requirements for sign supports (e.g., by size of sign panel), materials selection procedures, and sign mount- ing and hardware. • Guidelines for sign installation and maintenance. CHAPTER FOUR SIGNS

• Qualified products lists, sources, or vendors; procure- ment procedures. • Warranty requirements. Agencies may also specify their own sign material testing requirements (e.g., Florida Method of Test . . . 2000). MANAGEMENT PRACTICES Synthesis and AASHTO–FHWA Survey Findings In contrast with other selected assets discussed to this point, responsibility for sign maintenance resides much more closely with the owning agency. The distribution of work and 50 maintenance management responsibility reported by agencies participating in the study survey is shown in Figure 39. Al- though some DOTs reported contracting with private firms for sign maintenance, seldom did these firms have management responsibility. All of the local governments and Canadian provincial ministries that participated in the study survey maintained their own signs, with no involvement by other public or private organizations. In some cases, cities maintain signs on the state highway system within their municipal boundaries (e.g., in Kansas). Other aspects of asset management practice are revealed through agencies’ methods of budgeting for preservation, operation, and maintenance of road signs, and their No Response Other Agency Guidelines Public Policy Natíl. Standards Statutes Percentage of Responses 0 20 40 60 80 100 FIGURE 38 Technical management guidance for maintenance and rehabilitation of signs. Rank Factor 1 Public safety; accident and accident risk reduction 2 More efficient travel; maintain intended flow and operating speed; reduce travel time 3 Preservation of the existing road infrastructure; reduced agency life-cycle costs 4 Comfort and convenience of the traveling public (motorists, pedestrians, cyclists) 5 Road aesthetics and appeal TABLE 11 PRIORITY OF TRANSPORTATION OBJECTIVES SERVED BY ROAD SIGNS No Response Other Agency Guidelines Public Policy Nat’l. Standards Statutes Percentage of Responses 0 20 40 60 80 100 FIGURE 37 Technical management guidance for new installations of signs.

51 approaches to preserving and maintaining road signs once in service. Survey results for the budgeting method are shown in Figure 40. Explanations of the abbreviated budgeting process descriptions in this figure are given in chapter two. Because agencies could select multiple choices, the percentages in Figure 40 do not sum to 100%. Addressing their methods of budgeting, a large number of responding agencies at all lev- els of government chose the “staff judgments, political prior- ities, and citizen demands” option and the “previous budget plus adjustments” option as best describing their processes, followed by the two options involving performance targets. These descriptions were sometimes selected in combination with each other. The survey results in Figure 40 show that the number and target performance of assets are used to a degree in budget- ing; however, they are not the primary drivers of budget processes among survey respondents. Approaches based on Target [Asset Performance] Drives Budget, Budget [Asset Performance] Drives Target, and Percent of Inventory Budgeted Annually were identified in 19%, 31%, and 17% of responses, respectively. By contrast, methods based on Adjustments to the Previous Budget and those that involve Staff Professional Judgment, Political Priorities, and Citizen Demands each garnered almost 40% of the responses (bear- ing in mind that agencies could select more than one approach). The general thrust of these results is comple- mented by a January 2000 AASHTO survey of roadway safety hardware that was reported by the FHWA (Hensing and Rowshan 2005). When asked whether asset inventory and asset condition were used as the basis of funding alloca- tion, 10 of 39 states (26%) responded affirmatively for sign inventory, and 12 of 39 (31%) for sign condition—again, less than a majority in each case. The corresponding results for supports for signs, signals, and lighting in this AASHTO survey were 6 of 39 states (15%) responded affirmatively that funding allocation is based on supports inventory, and 11 of 39 (28%) that allocation is based on supports condition. A related question in the January 2000 AASHTO survey reported by the FHWA (Hensing and Rowshan 2005) asked whether state DOTs have a separate budget line item for maintenance of road signs, with 23 of 39 agencies (59%) responding affirmatively. The corresponding result for 0 20 40 60 80 100 No Response No Specific Approach Other Percent of Total Budget Judgment, Politics Previous + Adjustments Pct. Inventory Annually Budget Drives Target Target Drives Budget Percentage of Responses FIGURE 40 Annual budgeting method for sign preservation and maintenance. 0 20 40 60 80 100 Own Agency Private (Outsourced) Other Gov’t. Unit Other Entities No Response Pe rc en ta ge o f R es po ns es Mgmt. Resp. No Mgmt. Resp. FIGURE 39 Responsibility for maintaining signs once in service.

maintenance of sign, signal, and lighting supports was 8 of 39 agencies (21%) responding affirmatively. Although there was no corresponding question for the budgeting of new sign installations, the survey did address tracking and updating of asset inventory. These additional responses are reported later in this chapter. Agencies often described their approaches to preservation and maintenance as well in terms of multiple selections of the items shown in Figure 41. The immediate correction of prob- lems was most prevalent response, followed by preventive, prioritized, and worst-first approaches. Many agencies explained these multiple approaches by differentiating how and when they are used. For example: • An “Immediate” approach was identified for high- priority or critical signs having safety implications (e.g., Stop, Yield, Keep Right, Curve Warning, and Pedestrian Warning) by several agencies, including Pennsylvania, Vermont, Edmonton, and Portland. An immediate re- sponse was also noted for certain types of signs (New Brunswick) and sign damage resulting from severe weather (Saskatchewan). Edmonton reported that dam- aged high-priority signs are addressed within 2 h on a 24/7 basis, and Tampa also reported a policy of repair- ing sign damage that is phoned into the city’s Action Center within 2 h. • A “Preventive” policy was associated by responding agencies with programs of periodic inspection and repair by several agencies. The nature of these policies how- ever, and the frequencies of inspections, differ consider- ably. For example: – Kansas inspects signs in its High Performance Signing Projects on a 10-year cycle. – Tampa has a 12-year sign replacement cycle. – New Mexico cleans and straightens its signs on an annual basis; Portland conducts annual sign mainte- nance during nonstriping months. 52 – Pennsylvania conducts its preventive work on a 3- to 5-year cycle. – Edmonton performs area checks weekly to identify maintenance issues. Considerations in Improved Sign Management There are several considerations in managing the physical and operational performance of highway signs. • One is the choice of sheeting material, which plays a strong role in initial appearance and long-term perfor- mance of the sign, and affects its life-cycle costs. • A second is to be able to track the rate of deterioration in the sign’s visibility and legibility throughout its life. This reduction in the visual quality of the sign directly affects the ability of motorists, cyclists, and pedestrians to read, comprehend, and respond to the sign’s information. • A third is that because many signs are mounted in the roadside or on sidewalks they are susceptible to being hit by vehicles, potentially damaging the sign supports and the panel itself. As a safety measure, sign supports must be designed to break away or to absorb the energy of the crash to help protect the vehicle’s occupants. • Fourth, effective maintenance is needed to clean signs, repair damaged posts and panels, and replace signs when they have exhausted their service life. The FHWA has outlined several aspects of an improved sign management approach on its safety website. Consider- ations in implementing better management processes are given in the “Implementation” section. A component of this guidance concerns options to improve sign management (“Improving Traffic Sign Management . . .” n.d.), which include: • Developing a comprehensive sign inventory. • Developing or purchasing system software. 0 20 40 60 80 100 No Response Other No Maintenance Responsibility Deferred Maintenance Worst First Prioritized—Avail. Res. Corrected Immediately Preventive—Schedule Percentage of Responses FIGURE 41 Approach to maintaining and preserving road signs.

53 • Adjusting sign fabrication processes (e.g., to use higher quality materials). • Adding identifying codes (such as bar codes) to each sign. • Changing methods of sign procurement. • Using contract forces for some or all of sign inspection and replacement work. • Linking sign management to an agency’s other asset management practices. Guidelines prepared through the Minnesota Local Road Research Board (LRRB), with the participation of the MnDOT, are designed to assist cities and counties with traffic sign management. Best management practices in this docu- ment include (Montebello and Schroeder 2000): • Acquiring a sign management system or, at a minimum, a sign inventory system. These tools can help an agency identify, plan, budget, and track needs for sign work. • Use higher-grade reflective sheeting on more critical types of regulatory and warning signs (e.g., Stop, Yield, Stop Ahead, Yield Ahead, curve warnings) and wide- angle, microprismatic retroreflective sheeting at locations that benefit from these advantages: for example, where signs are at angles to traffic or must be located farther from the roadway. • Consider increasing the size of signs at locations with a history of safety problems or where the visibility of typical-sized signs would be limited. • Consider using signs that are larger and brighter than typical configurations in urban areas, where other activ- ities compete for drivers’ attention. • Explore bulk purchases of sign sheeting (e.g., tying into state DOT or other agencies’ purchasing contracts) to seek lower prices. The LRRB guidelines also provide an example of a life- cycle cost analysis of different sign sheeting materials. The results illustrate that higher-grade retroreflective materials result in lower long-term costs because of longer life and therefore longer intervals between sign replacements. Moreover, these re- sults do not include the increased benefits to road users owing to the higher initial and long-term retroreflectivity of superior grades of sign sheeting. The document also refers to a MnDOT life-cycle analysis comparing Type III and Type IX sign sheet- ing (these grades will be explained in the following section). The results showed that the materials cost accounted for a small percentage of total installation cost and that the higher-grade, higher-initial-cost Type IX sheeting was more cost-effective in the long term (Montebello and Schroeder 2000). MEASURING ASSET PERFORMANCE Managing Sign Retroreflectivity Many things can happen to signs over time to degrade their visibility to transportation users. Causes of deterioration can include color fading, loss of materials durability (e.g., crack- ing, curling, pitting, edge lifting, or blistering of sheeting), weathering, physical damage (e.g., from vehicle impact), obliteration resulting from dirt or sap accumulation, and van- dalism. One important measure of a sign’s ability to appear visible and understandable to road users, particularly at night, is its retroreflectivity. Retroreflectivity is the ability of a ma- terial to reflect light back toward its source. It is a property of the sheeting material used in the sign’s fabrication. In the case of highway signs that are not lit by road or street light- ing, the source of light is the vehicle headlamps; the retrore- flective sign sheeting redirects light back toward the vehicle, where it is perceived by the driver’s eyes. The coefficient of retroreflectivity compares the light returned to the driver’s eyes (luminance) with the light from headlamps incoming to the sign’s surface (illuminance). The units of measure are candelas per square meter per lux in the metric system, abbreviated cd/m2/lx (or, equivalently, cd/lx/m2), and in U.S. customary units, candelas per square foot per footcandle, abbreviated cd/ft2/fc (or, equivalently, cd/fc/ft2). The concept of retroreflectivity as it applies to highway signs is explained in the FHWA’s Roadway Delineation Practices Handbook (Migletz et al. 1994). At a series of 2002 FHWA-sponsored workshops on mini- mum levels of sign retroreflectivity, participants discussed their current practices in managing road signs. These ap- proaches included periodic nighttime visual inspections (and in at least one agency, training of personnel in nighttime sign inspections), formal statewide sign replacement programs (two agencies), sponsored research to measure sign retroreflectivity as a basis for predicting sign service life (two agencies), mobile automated measurement of sign fabrication or installation dates as a basis for age-based management of signs (at least two agencies), and sign inventory systems (at least five agen- cies) (Hawkins et al. 2003). Synthesis Survey Findings The information provided by agencies on performance mea- surement of road signs is summarized in Figure 42 based on categories of performance factors similar to those described in chapter two. Many agencies reported measures of physical condition and the corresponding qualitative descriptors, asset age, conformance to current standards, and customer com- plaints. Three municipalities (Edmonton, Portland, and Tam- pa) reported using asset value as one of the measures of per- formance. The frequencies with which physical performance measures are addressed are shown in Figure 43. The methods used by responding agencies to assess sign condition and performance are reported in Figure 44. Visual inspections and customer complaints are by far the most common methods used. Under “Other” methods, the city of Cape Coral, Florida, reported a commercial software pack- age for work history; Oregon reported a roadside inventory on construction projects; and Edmonton mentioned a system condition report based on estimated quantity and age of

54 0 10 20 30 40 50 60 70 80 90 100 No Response Other Customer Surveys Customer Complaints Asset Value QUAL: Other QUAL: Vandalism QUAL: Dirt Accumulation QUAL: Corrosion QUAL: Structural Condition QUAL: Nighttime Legibility QUAL: Daytime Legibility QUAL: Color Fading QUAL: Retroreflectivity Performance or Health Index Conform to Current Standards Asset Age PHYS: Other PHYS: Vandalism PHYS: Dirt Accumulation PHYS: Corrosion PHYS: Structural Condition PHYS: Nighttime Legibility PHYS: Daytime Legibility PHYS: Color Fading PHYS: Retroreflectivity Percentage of Responses FIGURE 42 Measuring performance of road signs. PHYS = physical; QUAL = qualitative. More Than Once A Year Annually Biennially Less Freq Than Biennially FIGURE 43 Frequency of physical condition assessments of road signs.

55 signs. Vermont noted that its use of video is only to comple- ment on-site inspections. Measuring Sign Retroreflectivity The FHWA website on sign retroreflectivity includes in- formation on sign retroreflectometers and reflectivity mea- surement (“Sign Retroreflectivity” n.d.). Because handheld retroreflectometers require multiple individual readings per sign, are time-consuming, expensive, and may require lane closures, MDOT has worked with the FHWA to develop a mobile evaluation of traffic signs system. This van-mounted system takes digitized pictures of a sign illuminated by a flash tube at a specified distance, and automatically computes its retroreflectivity. The van travels at highway speeds, enabling measurement of 300–400 signs daily. The flash tube is bright enough for measurements to be done in daytime. Benefits cited by MDOT include more reliable sign management and its positive implication for improved public safety, more complete data on sign performance over time, and cost- effectiveness as compared with manual retroreflectometer readings (Long 1997). Other studies describe additional methods and tools used to evaluate and analyze highway sign visibility and retrore- flectivity. For example, the luminance of the new types of microprismatic sign sheeting materials (Types VII, VIII, and IX) have been evaluated by computer simulation, using dif- ferent assumed roadway geometric layouts, vehicle dimen- sions and headlamp illumination levels, sheeting retroreflec- tivity values, sign placement, and viewing distances (Bible and Johnson 2002). Researchers at the University of Iowa have used their Traffic Sign Simulator Facility to test the luminance requirements (luminance contrast and background luminance) for symbol signs. These experiments have con- sidered several types of symbols, background luminance and complexity levels, and luminance contrast values. Given these variables, the researchers have assessed driver recogni- tion of sign meaning at two “comfort” or “confidence” levels (Schnell et al. 2004). Photometric modeling results do not always match the illuminance and luminance values mea- sured in the field. A study of one such group of inconsisten- cies has revealed the source of the problem to be pavement glare (Carlson and Urbanik 2004). Ketola (1999) has investigated the potential use of acceler- ated laboratory testing of retroreflective sign materials in lieu of outdoor testing. Although accelerated lab testing theoretically can yield several benefits, Ketola found that these procedures actually “are unreliable predictors of retroreflective sheeting durability, are more variable than expected, and are relatively expensive.” Outdoor evaluation is much more reliable and ide- ally should be conducted in a hot, wet climate (e.g., Miami, Florida); a hot, dry climate (e.g., Phoenix, Arizona); and a third climate as agreed on by the seller and purchaser. The data analyzed in this study suggest that a 36-month test period is a minimum requirement; shorter test periods may not give true indications of relative material durability. The author cautions, however, that even data from 36-month outdoor programs only address the question of minimum acceptable performance; they do not reliably predict the ultimate lifetime of sign materials (Ketola 1999). It has also been recognized that the headlamp illumination data used in modeling sign performance is based on lamps and mountings used in laboratory tests, rather than lamps in natural conditions mounted on a vehicle. Researchers have therefore outlined a method to measure illuminance at different points representing typical sign locations, from headlamps mounted on automobiles, motorcycles, light trucks, vans, and heavy trucks. These measurements will be conducted without aiming or cleaning the headlamps (Chrysler et al. 2002). No Response No Info. Collected Other Customer Complaints Customer Surveys Non-Destructive Testing Physical Measurement Photo, Video Visual Inspection 0 20 40 60 80 100 Percentage of Responses FIGURE 44 Data collection methods for sign condition and performance.

Minimum Sign Retroreflectivity Standards The FHWA has devoted considerable attention to methods, materials, and guidelines to promote more effective perfor- mance of traffic signs. A major focus of attention has been the retroreflectivity of highway signs, an issue that has been a high priority for the FHWA since the 1980s. Although this work has been driven, and continues to be strongly moti- vated, by the FHWA’s interest in highway safety, it was given additional impetus by an Act of Congress in 1993. Con- gress addressed the issue that whereas the MUTCD required signs either to be lit at night or to be retroreflective, it did not specify the minimum retroreflectivity required. Congress directed the Secretary of Transportation to revise the MUTCD to include a standard for the minimum levels of sign retrore- flectivity that must be maintained (Public Law 102-388 1993). (A similar requirement was also included for the min- imum retroreflectivity of pavement markings; see chapter five.) Over the past several years, the FHWA, working with highway industry constituents and stakeholders, has devoted considerable effort in meeting this directive. There have been a number of steps and iterations in this process, which have been described in several FHWA web documents and pub- lished research sources. Among these are: • An overview of FHWA efforts in retroreflectivity through the 1990s: “Overview of FHWA Efforts/Response,” 2006: http://safety.fhwa.dot.gov/roadway_dept/retro/gen/ overview_efforts.htm. • Minimum Sign Retroreflective Guidelines: Summary Report, FHWA RD-97-074, 1997: http://www.tfhrc.gov/ humanfac/97074/97074.htm. • FHWA Workshops on Nighttime Visibility of Traffic Signs, Summary of Findings, Report FHWA-SA-03- 002 (Hawkins et al. 2003): http://safety.fhwa.dot.gov/ roadway_dept/retro/sa03002/index.htm. • General information on sign retroreflectivity, current through 2003, with a description of sign sheeting mate- rials as of 2005: http://safety.fhwa.dot.gov/roadway_ dept/retro/sign/sign_retro.htm. • Maintaining Traffic Sign Retroreflectivity, Report FHWA-SA-03-027, 2003); Web version updated in 2005: http://safety.fhwa.dot.gov/roadway_dept/retro/ sign/sa03027.htm. • Examples of supporting research: – “Minimum Retroreflectivity for Overhead Guide Signs and Street Name Signs” (Carlson and Hawkins 2002). – “Comparison of Observed Retroreflectivity Values with Proposed FHWA Minimums” (Nuber and Bullock 2002). – Updated Minimum Retroreflectivity Levels for Traf- fic Signs, Report FHWA-RD-03-081 (Carlson and Hawkins 2003a): http://www.tfhrc.gov/safety/pubs/ 03081/index.htm. – Minimum Retroreflectivity Levels for Overhead Guide Signs and Street-Name Signs, Report FHWA- RD-03-082 (Carlson and Hawkins 2003b): http:// www.tfhrc.gov/safety/pubs/03082/index.htm. 56 – “Developing Updated Minimum In-Service Retrore- flectivity Levels for Traffic Signs” (Carlson et al. 2003). • “Maintaining Traffic Sign Retroreflectivity,” Notice of Proposed Amendments (NPA), MUTCD, Federal Reg- ister, July 30, 2004. • “Maintaining Traffic Sign Retroreflectivity,” Supple- mental Notice of Proposed Amendments (SNPA), MUTCD, Federal Register, May 8, 2006. The Federal Register SNPA is the most recent official step in the FHWA’s response to the Congressional directive requiring specification of minimum levels of sign retrore- flectivity. It responds to the comments received following the 2004 NPA, and has modified the NPA proposals in signifi- cant ways. Because the docket was still open as this report was being written, final rulemaking was not yet completed. In the SNPA, the FHWA is proposing an MUTCD Standard requiring agencies to use an assessment or management method to manage and maintain sign retroreflectivity at or above the minimums that will be defined in a new Guidance table to be included in the MUTCD. The proposed Guidance table bases recommended minimum retroreflectivity levels on the type of sign sheeting, sign color, size, and type of sym- bol or message. Sign sheeting types or grades are established using ASTM Standard D4956 and are explained in Table 12, based on information presented by the FHWA (Carlson and Hawkins 2003b). The SNPA proposes five options to maintain sign retrore- flectivity at or above the established minimum levels, but allows agencies flexibility to consider and use other effective methods. It also proposes eliminating the use of certain lower grades of sign sheeting for particular types of signs. There are many other details in the SNPA that (1) explain the background and ratio- nale of the proposed MUTCD amendments; (2) describe prac- tical steps that agencies can consider to comply with these provisions; and (3) address other matters, including questions and issues raised by stakeholders responding to the docket. Readers interested in these details should consult both the NPA and the SNPA (“Maintaining Traffic Sign Retroreflectivity” 2004; “Traffic Control Devices . . .” 2006). When minimum levels of sign retroreflectivity are finally established, they will provide a basis for strengthened sign management in several ways: • They will establish defined reference values for gauging service lives of different sign materials in terms of retroreflectivity, and projected replacement intervals. • They will strengthen the basis for life-cycle compar- isons of sign alternatives on the basis of performance (retroreflectivity) and long-term cost-effectiveness. • The assessment or management method called for in the SNPA should strengthen an agency’s sign-management capabilities, enabling it to track the condition of the sign inventory and anticipate replacement needs. • Having the legal requirement as well as an assessment or management method in place to maintain minimum

57 retroreflectivity levels provides a solid incentive and capability for agencies to prioritize sign replacement needs and allocate limited resources effectively. • The resulting better planning and programming of sign investment needs and the improved basis of resource allocation should contribute to greater safety and mobil- ity of the road system to the benefit of the public. • The improved visibility of signs expected to result from maintaining signs at or above minimums, coupled with the elimination or restricted use of lower-grade sheeting materials, will help older drivers, the numbers of whom are expected to increase. • It is understood that continuing research may result in subsequent updates of these minimum-value retrore- flectivity guidelines. ASSET SERVICE LIFE Synthesis Survey Findings Information on service life was obtained in the study survey for three major components of sign installations: (1) the sign panels including sheeting, (2) roadside sign posts, and (3) overhead sign bridges. Responding agencies were asked also to identify how they would determine service-life values. Responses to this question are shown in Figure 45. Among the 50% of reporting agencies that identified at least one method, their emphasis was on collective agency knowl- edge, whether represented by their experience with road sign infrastructure (e.g., a database of observed historical service lives) or by the professional judgment of their staffs. Manu- facturer’s data were also noted as a source of information, but to a lesser degree. Some agencies also reported the data used in life-cycle comparisons of different sign materials as a source of service-life information. Comprehensive service-life data reported by agencies in the study survey are given in Table 13. Examples of the distribu- tions of estimated service lives of sign components are shown in Figure 46 for sign sheeting, in Figures 47 and 48 for sign posts, and in Figures 49 and 50 for overhead sign bridges. The labels on the horizontal axis in these figures give the upper val- ues of each range of service-life data. For example, if these labels are 0, 2, 4, 6 . . . , then the column labeled 2 shows the number of responses for estimated service life of zero to 2 years; the column labeled 4, the number of responses for esti- mated service life of more than 2 to 4 years; the column labeled ASTM Type Designation Description I M edium -high-intensity retroreflective sheeting, so metim es referred to as “engineering grade,” and typically enclosed-lens, glass-bead sheeting. Typical applications for this material are perm anent highway signing, construction-zone devices, and delineators. II Medium -high-intensity retroreflective sheeting, sometimes referred to as “super engineer grade,” and typically enclosed-lens, glass-bead sheeting. Typical applications for this material are perm anent highway signing, construction-zone devices, and delineators. III High-intensity retroreflective sheeting that is typically encapsulated glass-bead retroreflective ma terial. Typical applications for this material are permanent highway signing, construction- zone devices, and delineators. IV High-intensity retroreflective sheeting. This sheeting is typically an unmetallized, mic roprism atic, retroreflective-elem ent ma terial. Typical applications for this material are perm anent highway signing, construction-zone devices, and delineators. VI I S uper-high-intensity retroreflective sheeting having the highest retroreflectivity characteristics at long and me dium road distances as determined by the RA (coefficient of retroreflection) values at 0.1° and 0.2° observation angles. This sheeting is typically an unmetallized, micro- prismatic, retroreflective-element material. Typical applications for this material are permanent highway signing, construction-zone devices, and delineators. VIII Super-high-intensity retroreflective sheeting having the highest retroreflectivity characteristics at long and me dium road distances as determined by the RA values at 0.1° and 0.2° observation angles. This sheeting is typically an unmetallized, microprismatic, retroreflective-element ma terial. Typical applications for this material are permanent highway signing, construction- zone devices, and delineators. IX Very-high-intensity retroreflective sheeting havi ng the highest retroreflectivity characteristics at short road distances as determined by the RA values at 0.1° observation angle. This sheeting is typically an unm etallized, mi croprism atic, retroreflective-elem ent material. Typical applications for this ma terial are perm anent highway signing, construction-zone devices, and delineators. Source: Carlson and Hawkins (2003b). TABLE 12 TYPES OF RETROREFLECTIVE SIGN SHEETING

58 No Response Do Not Use Service Life Other Manufacturer’s Data Professional Judgment Literature Agency Experience LCC Analyses Model Develop, MIS 0 20 40 60 80 100 Percentage of Responses FIGURE 45 Sources for determining service lives of sign components. MIS = management information systems; LCC = life-cycle cost. Component and Material No. of Responses Minimum (Years) Maximum (Years) Mean (Years) Median (Years) Mode (Years) Sign Sheeting All sheeting 17 7 20 11 10 Aluminum 3 7 40 19.8 11 — Vinyl sheeting 2 5 7 6 6 15 6 Sign Posts Steel U-channel 10 10 40 18.0 15 10 Steel square tube 10 10 40 16.3 15 10 Steel round tube 3 15 40 23.3 15 15 Aluminum tube 1 — — 10 — — Wood 3 15 20 16.7 15 15 Structural steel beam supports 2 25 30 27.5 27.5 — Overhead Sign Bridges and Supports Steel sign bridge 12 10 50 30.8 30 30 Aluminum sign bridge 8 10 45 26.9 30 30 Overpass/bridge mounting 1 — — 50 — — Notes: —, value is undefined for the particular distribution. When distribution is based on only one data point, its value is shown in the Mean column. TABLE 13 ESTIMATED SERVICE LIVES OF ROAD SIGN COMPONENTS

59 8 7 6 N o. o f R es po ns es 5 4 3 2 1 0 0 2 4 6 8 10 12 14 16 18 20 Estimated Service Life, Years FIGURE 46 Estimated service life of sign sheeting undifferentiated by reflective performance or color. 8 7 6 N o. o f R es po ns es 5 4 3 2 1 0 0 4 8 12 16 20 24 28 32 36 40 Estimated Service Life, Years 8 7 6 N o. o f R es po ns es 5 4 3 2 1 0 0 4 8 12 16 20 24 28 32 36 40 Estimated Service Life, Years FIGURE 47 Estimated service life of steel U-channel posts. FIGURE 48 Estimated service life of steel square-tube posts.

6, the number of responses for estimated service life more than 4 to 6 years; and so forth. It should be noted again that the data in Table 13 and Figures 46 through 50 may be derived in part from the professional judgment of agency personnel. In addition to the data in Table 13, agencies also provided more specific estimates of service life for different types of sheeting, differentiated by grade of retroreflectivity performance, color, or a combination of these attributes. Performance grade is given in terms of either the type of sheet- ing as defined by ASTM D4956 (see Table 12), or by product descriptions (e.g., high intensity, diamond grade). The addi- tional service-life data from survey respondents are as follows: • Maryland Type I 7 years Type III 10 years Type IV 10 years Type IX 10 years 60 • Pennsylvania Type I 7 years Type III 12 years • Utah Red 10 years Brown 10 years 40 Yellow 15 years Green 30 years White 15 years Blue 30 years • Vermont Type I or II (red) 5 years Type I or II (not red) 10 years Type III and above 15 years • High-performance or high-intensity sheeting Kansas 10 years New Brunswick 18 years Saskatchewan 10 years Tampa 12 years 8 7 6 N o. o f R es po ns es 5 4 3 2 1 0 0 5 10 15 20 25 30 35 40 45 50 Estimated Service Life, Years FIGURE 49 Estimated service life of steel overhead sign bridges. 8 7 6 N o. o f R es po ns es 5 4 3 2 1 0 0 5 10 15 20 25 30 35 40 45 50 Estimated Service Life, Years FIGURE 50 Estimated service life of aluminum overhead sign bridges.

61 • Diamond grade sheeting Florida 7 years Saskatchewan 12 years The structural performance of sign supports has also been a topic of recent interest. Research has resulted in updated guidelines and specifications for structural supports (Stan- dard Specifications for Structural Supports . . . 2001, updated in 2003; Fouad et al. 2003). Other Data on Sign Materials and Service Life • The FHWA has produced a two-page “Retroreflective Sheeting Identification Guide” (2005) that organizes sheeting by its two basic retroreflective surfaces: glass bead and prisms. Within each of these groups, the guide identifies the ASTM grade, associated manufacturer and brand name and series number, and relevant notes. • The Minnesota LRRB guidelines include a sign sheet- ing matrix that identifies, for each type of sheeting, the retroreflective mechanism (e.g., different types of lenses or beads, or microprismatic), estimated cost, anticipated service life, life-cycle costs, initial retro- reflectivity, and advantages and disadvantages. The estimated service lives are as follows (Montebello and Schroeder 2000): – Type I: 5–7 years – Type II: 5–7 years – Type III: 14 years – Type IV: Not available – Type VII: Not available – Type VIII: 15–20 years – Type IX: 15–20 years • The Federal Register SNPA cites data on typical ser- vice life for selected sheeting types based on a 1996 FHWA study (“Traffic Control Devices . . .” 2006): – Type I: 7 years – Type III: 10–12 years The SNPA proposes eliminating the use of Type I sheeting for warning signs and for legends on ground-mounted guide signs. Types I, II, and III would be unacceptable for legends on overhead signs. These provisions are intended to help older drivers (Carlson et al. 2003; “Traffic Control Devices . . .” 2006). • The Kansas DOT lists minimum coefficient of retrore- flection values by sheeting color, ranging from 200 cd/m2/lx for white to 9 cd/m2/lx for brown (Special Pro- vision . . . 1990). The Delaware DOT also specifies min- imum coefficients of retroreflection according to color, as well as observation and entrance angles (functions of the distance between sign and observer and the offset distance to the sign from the travel lane with the sources of headlamp light) (Traffic Control Manual n.d.). Other DOT guidelines that were reviewed specify the grade of sheeting required by sign classification, but do not include a minimum retroreflectivity. The Minnesota LRRB guidelines for local government agencies include minimum retroreflectivity recommendations in a series of tables based on type and color of sign background and legend, type of symbol, size of sign, and traffic speed (Montebello and Schroeder 2000). • The Minnesota LRRB guidelines include an example of life-cycle cost analysis of sign sheeting materials. The results demonstrate the cost-effectiveness of better grades of sheeting (Montebello and Schroeder 2000). The potentially lower life-cycle cost of using more durable grades of sheeting is also cited as a rationale in support of the FHWA’s SNPA minimum retroreflectivity proposals (“Traffic Control Devices. . .” 2006). • Materials and dimensions for sign posts are also included in the agency guidelines listed previously. Current practices and state of knowledge for sign sup- ports, particularly posts and structures for larger signs, have been updated in NCHRP Report 494 (Fouad et al. 2003). Innovation in smaller sign supports is illustrated by Caltrans’ field experiments with a new, reusable sign post foundation that reduces exposure of mainte- nance crews to traffic when replacing damaged posts (White et al. 2000). A life-cycle cost analysis of alter- native materials has been illustrated based on data from the Kansas DOT (Raman et al. 2005). • The North Carolina DOT has a study underway to model the durability of road sign performance as a basis for predicting sign replacement needs. The agency has collected data on the degradation in sign retroreflectivity, together with sign location (GPS), sign message, type and color of sheeting, sign age, and a photograph of the sign. Threshold levels of retro- reflectivity have been developed by type of sheeting and sign color as a basis for determining end-of-service life and need for replacement. From these data, the North Carolina DOT has estimated the rate of deterio- ration by sheeting type and color. The modeling ap- proach is a simulation of the in-service inventory of signs to predict the number of deficient signs each year. This result can then be translated to a projected cost of sign replacement. The analysis is performed in a spreadsheet (Harris et al. 2005). • A facility for nationwide calibration of retroreflectome- ters has recently been established at the National Insti- tute for Standards and Technology. The Center for High Accuracy Retroreflective Measurements will standard- ize and certify the measurement of retroreflection on reference artifacts that can be distributed to agencies for calibrating their own retroreflectometers (NCHRP Research Results Digest 297 . . . 2005). These certified national calibration standards are a necessary step in improving the accuracy in readings among different retroreflectometers; ensuring an accurate and reliable implementation of proposed minimum retroreflectivity

levels for signs; and contributing to the public safety on the nation’s road system. Determining Current Asset Status To apply the service-life concept in asset management a method is needed to determine where an asset is in its service life—that is, how much life is consumed, and how much remains. Agen- cies were presented with a number of ways to determine the cur- rent status of an asset regarding its service life, and asked to rank each method by relevance to their agency. The results are shown in Table 14. Note that two instances of tie values occurred in this particular ranking process. The “Other” factors in Table 14 included the following: • Check sticker dates on the signs (Colorado Region 4); • Use commercial software to track work history (Cape Coral, Florida); and • Some districts look at the nighttime legibility of their signs to determine service life (Oregon). On the related issue of identifying the extension in service life owing to maintenance, none of the reporting agencies responded affirmatively. INFORMATION TECHNOLOGY SUPPORT Synthesis Survey Agencies participating in the study survey identified their key IT capabilities as shown in Figure 51. More than half of the agencies have an inventory of road sign assets accompanied by information on location. Asset age, maintenance and inspection data, and anticipated service-life information were also mentioned by a number of respondents. No strong 62 distinctions in the findings represented by Figure 51 were observed among different levels of government. By compar- ison, responses to the January 2000 AASHTO survey reported by the FHWA (Hensing and Rowshan 2005) indi- cated that 24 of 39 agencies (62%) had an inventory of signs, and most of these updated their inventory by either manual surveys or semi-automated methods. Agencies characterized their IT systems for road signs as shown in Figure 52. The greatest number of responses per- tained to broad-based management systems (such as main- tenance management systems) followed by workbooks or spreadsheets, sign management systems, and simple programs. “Other” options mentioned by agencies included a videolog and use of crew-leader log books to record data initially, with subsequent transfer to electronic format. The agencies that reported using a road sign management system or a maintenance management or transportation infrastruc- ture asset management system that includes road signs are listed here. • Road Sign Management System – Arkansas DOT – Michigan DOT – South Carolina DOT – Vermont AOT – Colorado DOT Region 2 – Saskatchewan Highways and Transportation – Dakota County, Nebraska – City of Tampa, Florida. • Maintenance or Asset Management System That In- cludes Road Signs – Florida DOT – New Mexico DOT – North Carolina DOT – North Dakota DOT Rank Factor 1 Monitor condition of asset on a periodic schedule 2 Assets are repaired or replaced as soon as they fail without regard to service life 3 Compare current age of asset with maximum age that defines service life 4 Monitor condition of the asset occasionally 5 Service life is often determined more by functional obsolescence than by wear and tear 6 Assets are replaced on a preventive maintenance schedule without regard to where they are in their service life 7 The agency does not use/does not monitor service life for this type of asset 8 Apply deterioration models to estimate where the asset is on “the curve” 8 Other TABLE 14 RANKING OF METHODS TO DETERMINE WHERE ROAD SIGN ASSETS ARE IN THEIR SERVICE LIVES

Simple Program(s) for this Asset Broad-Based MMS, TIAMS, etc. Signal Management System Percentage of Responses Workbook, Spreadsheet Other Products or Procedures 0 20 40 60 80 100 FIGURE 52 Types of analytic tools to support road sign management. MMS = maintenance management system; TIAMS = transportation infrastructure asset management system. 63 0 10 20 30 40 50 60 70 80 90 100 No Response None of the Above Other Historical Database PMs, Dashboards, Accountability GIS Maps, Reports GIS Interface Est. Asset Impacts on Public Track Public Comments Cost Models for Treatments Other Optimization Procedures Benefit-Cost, LCC Decision Rules or Trees Inspector Recommendations Established Mntce. Schedule Deterioration Models Anticipated Service Life Dates of Inspections, Assess. Asset Age Usage, Traffic Volume Photograph Current Condition, Performance GPS Coordinates Location (e.g., Rte-Milepost) Number/Quantity of Asset Percentage of Responses FIGURE 51 IT capabilities to help manage road signs. GPS = global positioning system; LCC = life-cycle cost; GIS = geographic information system; PMs = performance measures.

– Utah DOT – Colorado DOT Region 5 – New Brunswick DOT – City of Cape Coral, Florida – City of Portland, Oregon. Two agencies mentioned partial implementations of sign management programs and databases. In one instance, an agency-developed program was adopted by some, but not all, regions. In the other case, sign management districts with independent responsibility for their respective sign inventories have developed and use their own IT programs and databases. Other Data on Sign-Related Systems In 2002, at a series of FHWA-sponsored workshops on min- imum levels of sign retroreflectivity, participants discussed their current sign management practices and tools. At least five agencies mentioned sign inventory systems (and three were contemplating such systems), which are typically linked to geographic information systems (GIS) data. One agency automated its data uploading using handheld per- sonal digital assistants (PDAs). Although these systems generally lacked information on sign retroreflectivity, they could be modified to include such information in the future (Hawkins et al. 2003). NCHRP Project 4-29, Selection of Materials to Optimize Sign Performance, has been completed and an interim report is available at this time. The objectives of this project are to develop a simple, user- friendly decision-making tool that will aid transportation agen- cies in the selection of retroreflective materials for traffic signs, based on roadway conditions and other factors that most criti- cally affect sign performance. Appropriate selection must also take into account sign design and placement decisions. The decision-making tool should be appropriate for use by traffic authorities at the local, county, regional, state, and federal levels and by consulting engineers. It should be suitable for an agency’s sign installation and management functions and provide procedures for policy development, new sign requests, system upgrade decisions, and safety analyses. — Source: “Selection of Materials . . .” 2006 The Minnesota LRRB guidelines describe data elements that can be included in a sign inventory system for local governments. • Basic information—sign location within the highway system, position with respect to the road (e.g., left, right, and overhead), MUTCD or other identifying code, current sign condition, and maintenance history with dates. • Additional technical information—sign size, installa- tion date, type of sheeting, type of substrate or backing, type of post or support, condition of post or support, sign orientation (cardinal direction in which the sign 64 faces), and speed limit of the roadway on which the sign is located. • Detailed technical information—sign offset (from the edge of the pavement), height, retroreflectivity data, identification of inspector, sign identification number, photolog or videolog of sign, comments or annotations regarding the sign, its condition, etc., and any other reference numbers needed (e.g., district location, applic- able contract numbers, and plan numbers). If the provisions of the current FHWA SNPA become a Standard within the MUTCD, they will require agencies to apply management methods to maintain sign retroreflectivity at or above the specified minimums (“Traffic Control Devices . . .” 2006). These methods may well include some type of IT data or management system support. KNOWLEDGE GAPS AND RESEARCH NEEDS Synthesis Survey The many comments received in the study survey regarding knowledge gaps and research needs in sign management fell into several groups. • The topic mentioned most often in these comments was the need for a sign management inventory system, and the importance and difficulty of keeping this inventory up to date once the initial database is developed. At least eight agencies referred to this issue; some are now actively developing such systems and databases. • Two agencies referred to the difficulty of gaining atten- tion for sign management issues. Oregon observed that signing is a relatively low-budget, roadway item; there- fore, there is little incentive to develop a management system when districts do a reasonably adequate job of maintaining their signs based on field judgments. Utah noted a lack of a perceived need for sign management, as opposed to “fix what’s knocked down.” • A few agencies mentioned shortcomings of retroreflec- tometer readings (too variable) to use in determining sheeting life and the desire for a low-cost, efficient method to evaluate sign retroreflectivity. • Several agencies identified the need for a more compre- hensive understanding of the degradation in sign legi- bility and retroreflectivity over time as a function of several variables, including location, orientation, sun- light exposure, sheeting type, climate (the northern U.S. climate was mentioned specifically by Saskatchewan), aging, and vandalism. A related comment mentioned the need for survival curves that capture these relation- ships. • At least two agencies mentioned the desirability of bet- ter understanding the actual needs of drivers with respect to sign condition and performance. • Several gaps in technical knowledge and a desire for related research were noted by agencies:

65 – To understand the benefit–cost and comparative ser- vice lives of different types of sign sheeting, such as high-intensity sheeting versus the new prismatic sheeting. – A related comment observed that new products emerge continually and it may be difficult to test service life of sheetings that will not have failed before new models become available. – To understand the effect of a new wood preservative treatment (alkaline copper quaternary, or ACQ) on retroreflective sheeting. – To understand the effect of deicing materials on retroreflective sheeting. Research Needs Identified in the Literature The 2002 FHWA workshops on sign retroreflectivity identi- fied several unanswered questions. Although some have been implicitly addressed in the recent FHWA SNPA, at least in the interim, they will likely remain of interest to the highway com- munity even as research continues. Other questions reflect unmet research needs. The complete list of questions compiled at the workshops is as follows (Hawkins et al. 2003, chapter 3): What is the impact of ambient lighting on the visibility of signs? Can intersection and street lighting provide sufficient luminance without retroreflectivity? Should minimum levels represent best case, typical case, or worst case scenarios? How will agencies develop accurate information on sign sheeting service life as a function of sheeting type, exposure direction, color, and other factors? What is the impact of product lines changes on previous data about sign service life? What driver characteristics are of greatest concern? How does driver age relate to the types of vehicles driven? How many older drivers actually drive at night? How can agencies stop the trend of headlamps directing less illumination toward signs? It is worth noting that the participants felt that it is not appropriate for agencies to assume the increased costs of improving the infrastructure that result from changes in automobile manufacturing standards. Headlamp performance changes every few years while signs that agencies install are intended to last at least 7–10 years, often longer. Participants felt that headlamp changes that impact traffic control device perfor- mance should be limited or better coordinated with the trans- portation agencies. A few participants even suggested that automobile manufacturers should provide funding for traffic control device improvements while changes are made. Workshop participants also expressed a desire for the FHWA to develop performance-based information that would more strongly link nighttime sign visibility to reduced nighttime crashes. Discussions with the FHWA indicate that they are proceeding with such a research project. The TRB Millennium Paper on signing and marking materials cites materials performance, in both durability and utility (i.e., to motorists), as a hallmark of future state of the art. Examples of materials that are anticipated to become more widely used in road signs are fluorescent materials, wet-reflective materials, and new materials such as corner- cube sheeting and all-plastic sign panels (Kalchbrenner 2000). Ongoing testing of signage products is carried out by the National Transportation Project Evaluation Program (NTPEP), sponsored by AASHTO and its member agencies. NTPEP conducts laboratory and field tests on various mate- rials at sites in four climatic zones around the country, and publishes results on performance for participating agencies (Thomas and Schloz 2001). As of 1999, outdoor testing of sign sheeting through NTPEP had been conducted in Arizona, Louisiana, Minnesota, North Carolina, and Virginia (Ketola 1999). NTPEP results are expected to be used increasingly by AASHTO member agencies when selecting signage materials and products. A second Millennium Paper on vehicle user characteris- tics addresses human factors issues at both ends of the driver age spectrum, as well as general driver comprehension of, and response to, traffic control devices. With respect to asset management, the key human factors issues are those associ- ated with older drivers. These knowledge gaps and research needs are in the following areas (Ranney et al. 2000): • Data on the impairments that older drivers may have with driving-related vision, attention, cognition, and physical impairments, and the distribution of these char- acteristics among the elderly population. • Epidemiological studies of age-related medical condi- tions that potentially increase the risk of collision, and research using simulation and instrumented vehicles to establish older-driver performance as affected by these medical conditions. • Further applications of simulation and instrumented vehicles to determine how older-driver performance is affected by ITS components, and to what degree these innovations are accepted and accommodated by older drivers. • Related topics that need to go into older-driver educa- tion programs. This Millennium Paper observes that sign specifications and elements such as letter heights in the MUTCD have traditionally been based more on road design speed than on driver needs. Moreover, such standards have been calibrated to the performance of young drivers during daylight; when the needs of older drivers in nighttime are considered, recent studies suggest that revisions in current standards may be needed. Moreover, computer models that are now used to predict driver reaction to signs, particularly those signs that require drivers to act before a sign is reached, need to be updated to predict the retroreflectivity required for nighttime visibility and sufficient time to respond across the driver

population, including older drivers (Ranney et al. 2000). (Some of this research has been accomplished in support of the FHWA’s SNPA for minimum retroreflectivity levels; but again, ongoing interest in this topic and continuing research are likely in the future.) Research is also needed on driver comprehension and improved design and the use of signs that are not now well understood, such as certain symbol signs that have replaced word signs and intersection schemes combining geometric layout, signage, and delineation that 66 vary from one another and may cause driver confusion (Ranney et al. 2000). Among the top 16 research priorities identified by the TRB Pedestrians Committee, one research problem state- ment addressed signs: “Evaluation of MUTCD Signing, Markings, and Traffic Signals for People with Visual Impairments, Children, and Elderly Adults” (Transportation Research Circular E-C084 . . . 2005).