Development of Levels of Service for the Interstate Highway System (2010)

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92.1 Overview A state-of-the-practice review was performed to identify approaches used by the federal government and state depart- ments of transportation to measure and report highway LOS. This included identifying approaches used to aggregate facility- level data to report level of service by functional class and/or dis- tinguishing between highways within metropolitan boundaries and outside those boundaries. For the most part, a scan of secondary sources was used to establish the state of the practice, particularly the following research reports: • NCHRP Report 551: Performance Measures and Targets for Transportation Asset Management, NCHRP Project 20-60, 2006 and • NCHRP Report 632: An Asset-Management Framework for the Interstate Highway System, NCHRP Project 20-74, 2009. In addition to the published research, the research team members were personally familiar with relevant practices in about a dozen state DOTs. Much of this knowledge is not pub- lished and was particularly helpful for the assets other than pavements and bridges, such as drainage features, traffic con- trol devices, and roadside features. Members of the research team also attended the Second National Maintenance Quality Assurance Peer Exchange, held in Raleigh, NC, September 22–23, 2008. The project workshop, held in October 2009 and attended by project panel members and representatives from the three demonstration states (Florida, Mississippi, and Washing- ton), provided additional insight on LOS practices. This group included representatives from eight state DOTs, a county road agency, AASHTO, and the academic and consulting communities. These sources provided a firm basis for establishing the state of the practice. 2.2 Framework for Research Results The earlier research (NCHRP Report 632) defined several broad categories of national objectives for LOS measurement that were helpful for categorizing the research results. These objectives or outcome areas are as follows: • Preservation—Research on this outcome area was related to preservation of assets, sometimes referred to as preservation of investment. LOS measurement practices were found to be in wide use for most assets, including pavements, bridges, drainage, traffic control devices (active and passive), and a few other roadside assets on the IHS. • Mobility—Research on this outcome area, sometimes referred to as “operations reliability,” found that most LOS measures were related to traffic congestion. • Safety—The safety outcome area covers the systematic mon- itoring and reporting of fatalities, injuries, and crashes on the highway system. LOS measures for this outcome area are usually expressed in terms of a rate based on vehicle miles of travel. • Environment—State DOTs may refer to this outcome area as environmental quality, environmental protection, envi- ronmental preservation, or environmental stewardship (for this project, the latter term was preferred). Although all states routinely perform environmental assessments of their pro- grams and projects, and undertake various mitigation meas- ures, there was very limited data on LOS measurement and reporting for this area. Since the purpose of asset management is to help transporta- tion agencies better achieve their policy goals, the policy goals of the three demonstration states used in this study (Florida, Mississippi, and Washington) were reviewed to ensure that any LOS measures developed for IHS application would support these goals. Table 2-1 was developed from information found on the DOT web sites for these states. C H A P T E R 2 Summary of the State of the Practice

Florida Mississippi Washington Economic Prosperity Economic Development (No equivalent goal) Environmental Preservation Environmental Stewardship Environmental Protection Mobility Accessibility & Mobility Mobility Preservation Maintenance & Preservation Preservation Safety Safety Safety & Security (No equivalent goal) (No equivalent goal) Stewardship (Quality, Effectiveness, Efficiency) The goals of preservation, mobility, safety, and environmen- tal stewardship were common to all demonstration states and are aligned well with the core service-level categories proposed in Table 2.2 of NCHRP Report 632 for grouping asset perfor- mance measures. These four policy goals will be aligned with the recommended performance measures in Chapter 3 of this report. Economic development, or economic prosperity, mentioned by two of the states, was not included since that goal is much broader in scope and influenced by many factors other than IHS LOS. The same could also be said for environmental stewardship, except that some states have incorporated specific environ- mental mitigation measures into their highway planning, design, construction, maintenance, and operational practices. For example, Washington DOT installs culverts such that the water flow will not restrict fish passage. Some states also mon- itor compliance with environmental agreements and mitiga- tion measures. Although there are no specific LOS measures as such, a few states use a simple checklist approach to ensure that environmental issues are not overlooked. Accordingly, environmental stewardship was included mainly to serve as a reminder that it should not be overlooked during asset man- agement considerations. However, at present, the state of the practice offers no specific guidance on performance measures that would be applicable to the IHS. 2.3 Asset Classes The state-of-the-practice research led the research team to disaggregate IHS assets into the following logical asset classes. For each asset class or outcome area listed below, a recommended LOS framework was developed based on the state-of-the-practice research. 2.3.1 Pavement The pavement asset area includes roadways, shoulders, ramps, and other paved areas. The state-of-the-practice review finds strong evidence that a national framework for measur- ing and reporting system-level LOS for the nation’s Interstate pavements can be implemented that builds on the data collec- tion and reporting performed through HPMS. Such measure- ment can address ride quality and distress. Several conclusions can be reached from the literature review of state highway agency pavement management practices, including • All agencies collect pavement roughness information, typ- ically expressed in the form of the International Roughness Index (IRI). • All agencies collect pavement distress information as a means of identifying structural deficiencies. • Most agencies develop a distress index scale that is used to provide an overall measure of pavement condition. Table 2-2 shows the state-of-the-practice research results for pavement assets. 2.3.2 Structures The structures asset class focuses on bridges, but also includes large culverts (span greater than 20 ft), overhead sign and sig- nal structures, and retaining walls. The state-of-the-practice review finds strong evidence that a national framework for measuring and reporting system-level LOS for the nation’s Interstate bridges can be implemented that builds on the fol- lowing two ongoing and related efforts to improve the measure- ment and reporting of the performance of the nation’s bridges: 1. The use of the AASHTO Guide for Commonly Recog- nized (CoRe) Structural Elements to provide data to establish a common Health Index (first developed by Caltrans) and 2. Computing the Health Index using data collected by all 46 states that are currently using Pontis to manage their bridge inspection data. 10 Table 2-1. Policy goals of the demonstration states.

Asset Class Level of Service Condition Indicator Measure Structures Structural and functional condition of decks, superstructure, substructure, and culverts Deck rating: superstructure rating; substructure rating; culvert rating; clearances (horizontal and vertical) Average National Bridge Inspection (NBI) condition rating Load-carrying capacity Superstructure rating; substructure rating; traffic volume and composition; load rating Structural evaluation; NBI Load Rating Overall structural and functional condition Structural adequacy and safety; serviceability and functional obsolescence; essentiality for public use Sufficiency rating Element level structural condition CoRe element condition states Health Index; element average condition state Note: Asset elements would be defined to be consistent with the agency’s current bridge management practices. Asset Class Asset Elements Level of Service Condition Indicator Measure Pavement Travel Lanes: Functional/ Structural Ride quality/ structural capacity International Roughness Index, rutting, faulting, fatigue cracking, and transverse cracking Mean Roughness Index, average rut depth, average fault, % fatigue type cracking, and length of transverse cracking (ft/mi) Ramps: Functional/ Structural Ride quality/ structural capacity International Roughness Index, rutting, faulting, fatigue cracking, and transverse cracking Mean Roughness Index, average rut depth, average fault, % fatigue type cracking, and length of transverse cracking (ft/mi) Shoulders Functioning as designed Adequate/inadequate, potholes, edge raveling Extent of shoulders inadequate (percent) Tunnels were not included as an asset class for LOS pur- poses because they are not included in the CoRe elements by AASHTO and they occur in relatively small numbers on the IHS. Table 2-3 shows the results of the structures state-of-the- practice research. 2.3.3 Other Interstate Assets Many states collect condition data on roadway assets as a part of their MQA programs. The aim of these programs is to establish LOS ratings for each of those assets for performance evaluations and, in some cases, to develop a performance- based maintenance budget. These assets typically include drainage, traffic control devices, and other roadside features, as follows: • Drainage—The different surface and subsurface drainage assets within the IHS drainage systems are culverts and pipes, ditches, drop inlets and catch basins, and other drains. Culverts are drainage structures 20 ft or less in span length, measured in the direction of travel. Pipes may 11 Table 2-2. Pavement state of the practice. Table 2-3. Structures state of the practice.

provide lateral or transverse drainage and may be described as cross, side, or outfall drains. Ditches can be unpaved or paved to prevent erosion and improve flow. Drop inlets and catch basins are drainage structures that collect storm water surface runoff and transport it to a culvert or storm water sewer system. Edge drains and under-drains are located under the roadway and along the edge of a shoul- der or curb. • Roadside—The roadside asset class is the area between the outside edges of the shoulder and the right-of-way line. For the IHS, this is best defined as all non-paved areas within the Interstate right of way, and includes slopes, mowable areas, brush and tree areas, and fences. Rest areas are also included in this class and include all roadside facilities where parking is permitted, such as visitor centers, information kiosks, pic- nic areas, scenic vistas, and historic monuments. • Traffic Control and Management Devices (Active)—This category includes all of the equipment installed on and along the roadway and in control centers that is used for active traffic management, including signals and what is gener- ally referred to as Intelligent Transportation Systems (ITS). However, the state of the practice has not reached the point where LOS measures have been developed and applied in sufficient numbers to serve as a guide for national applica- tion. Furthermore, these devices are generally not found in rural areas that make up most of the Interstate mileage. At present, active traffic control devices are not recommended for Interstate LOS assessment. • Traffic Control and Management Devices (Passive)—Traffic control devices in this category are signs, pavement mark- ings, delineators, guardrails, and other devices used to regu- late, warn, or guide traffic. They may be placed on, over, or adjacent to the highway. The purpose of such devices is to move vehicles safely and efficiently by guiding traffic move- ment, controlling vehicle speeds, and warning drivers of potentially hazardous conditions. Highway lighting was considered for inclusion in the “other IHS assets” category for LOS assessment. However, this item was not included for practical reasons. For lighting to be adequately addressed for LOS purposes, a separate night- time inspection would be needed, at considerable additional effort and cost. The research team concluded that the addi- tional cost of nighttime data collection outweighed any benefit to be gained. Table 2-4 through Table 2-6 show the state-of-the-practice research results for drainage, roadsides, and passive traffic control devices. 2.3.4 Other Outcome Areas The outcome areas of mobility, safety, and environment are not directly related to specific asset classes or asset LOS, but are related to how well the assets are being managed to meet the objectives of mobility, safety, and environmental stewardship. Mobility and safety are particularly well suited as IHS LOS indicators, since the IHS was originally conceived and constructed to provide safe, high-speed travel over long distances. State-of-the-practice results for these outcome areas are summarized below. 2.3.4.1 Mobility This category describes how well the transportation network is performing its basic function of supporting transport, often expressed in terms of throughput and congestion. Previous research efforts, including NCHRP Projects 20-74 and 20-60, concluded that state practices vary widely. Definitions, goal areas, and data collection and analysis techniques create diffi- culties for meaningful comparison of LOS measures between states. NCHRP Report 632 (Project 20-74) recommended only two mobility indicators (i.e., travel time and delay) derived from measures that are currently available in the HPMS. Although the state-of-the-practice research did not find much commonality among the states to allow a concise state- ment of practices, there were sufficient measures and data available to warrant development of a few key LOS indicators and measures for mobility, as shown in Table 2-7. 12 Asset Class Asset Elements Level of Service Condition Level of Service Indicator Deficiency Criteria Level of Service Measure Drainage Systems Point features: Drop Inlets/Catch Basins Functioning as designed Blocked/damaged Percent blocked/damaged Percentage of elements blocked/damaged (number of elements deficient divided by total number of surveyed elements) Linear features: All cross and side drainage structures, and ditches Table 2-4. Drainage state of the practice.

13 Asset Class Asset Elements LOS Condition LOS Indicator Deficiency Criteria LOS Measure Roadside Front and Back Slopes Functioning as intended Erosion, slides Depth of washouts, depth of accumulated material Percent of slopes deficient (measured longitudinally along roadway) Right-of-Way Fences Functioning as intended Missing/damaged Height reduction, openings Percent of length deficient Vegetation Management Condition of mowable areas Motorist visibility, aesthetics Height of vegetation in mowable areas Average height of vegetation (inches) Rest Areas Open and functioning as intended Closed; damaged facilities; non- functioning facilities; not sanitary; unsightly Rest area rating Average rest area rating (five- point scale) Table 2-5. Roadside state of the practice. Asset Class Asset Elements LOS Condition LOS Indicator Deficiency Criteria LOS Measure Traffic Control & Management Devices – Passive Point features: All signs, delineators, hazard markers, impact attenuators, pavement symbols & legends Functioning as designed Non-reflecting/ missing/ damaged/ obstructed Quantity deficient Percentage of elements deficient Linear features: All pavement stripes and markings, guardrails, barriers Table 2-6. Traffic control and management devices (passive) state of the practice. Outcome Area Units of Analysis Service Level Condition Service Level Indicators Deficiency Criteria LOS Measures Mobility Statewide, metropolitan planning organization (MPO) area, non-MPO area Mobility, operations reliability Delays, congestion Frequency of on-time arrivals; frequency of congested travel; traffic volume versus capacity Percent on-time arrival, percent heavily congested travel, volume/capacity ratio Table 2-7. Mobility state of the practice.

2.3.4.2 Safety A well-developed state of the practice exists for measuring and reporting safety outcomes at the national and state levels. Transportation safety has long been a policy priority, with the systematic monitoring and reporting of crashes, fatalities, and injuries on the highway system. The U.S.DOT and state DOTs all monitor and report safety performance. The federal govern- ment and state agencies have broadly consistent approaches to reporting safety outcomes, especially for fatalities, with LOS measures that are applicable to the IHS. The state-of-the- practice research results are shown in Table 2-8. 2.3.4.3 Environment Environmental outcomes typically are not addressed by state DOTs in terms of LOS measures. Most of the policy statements and performance measures currently in use, such as air and water quality measures, are specific to other agen- cies. The measures are not applicable to the IHS as a unit of analysis distinct from other highways or other sources. Some practices currently used by a few DOTs—such as checklists to ensure compliance with environmental agreements and mit- igation measures—while effective at the managerial level, are generally state-specific and would not be transferable to other states. The research team concluded that the current state of the practice does not provide sufficient guidance from which to develop environmental LOS measures for the IHS or for attempting to isolate the IHS from other highway systems or from other sources. Furthermore, the state of the practice does not provide guidance on differentiating the contribu- tions to environmental quality from the IHS, other highway systems and other sources. In some respects, the LOS measures included in the mobil- ity outcome area are related to environment quality associ- ated with IHS operations. For example, measures such as traffic volumes, delays, and congestion have a relationship to air and water quality and noise levels. But, how these meas- ures should be treated in an environmental LOS context is beyond the current state of the practice. 2.4 Findings Our state-of-the-practice research provided the following findings: • All state highway agencies are currently collecting pavement and bridge condition data and safety-related data, with vary- ing degrees of sophistication. Common to all are the data items collected as part of national inspection and reporting requirements (i.e., HPMS, the NBI program, and FARS). • Based on the literature search and the research team’s experience in various states, over 30 state highway agencies are currently collecting condition data on selected other assets, including drainage and roadside features, traffic con- trol devices, and rest areas. There is considerable variation between the states in their practices, although there is much commonality in the use of the data. • Although there are some technical issues to be resolved, such as standardization of measurements and rating crite- ria, none of these issues appear to be insurmountable. • There are no known technology limitations that would pre- vent any state from embarking on a comprehensive LOS assessment program—in fact, there are several technologies currently available that make the task easier (e.g., instru- mented vans for pavement data collection and video logging, GPS-capable handheld data collection devices, handheld laser rangefinders for measuring lengths and distances, GIS applications to assist in analyzing and presenting the data, and commercial off-the-shelf software applications for man- aging the data). • FHWA has already established a precedent for nationwide collection of standardized highway asset data (i.e., the HPMS that has been in operation for over 20 years). Although changes in HPMS reporting requirements are planned for 2010, the data will continue to serve the same purpose. • It is technically possible to establish an IHS LOS system. Key elements of the system already exist nationwide for pave- ments, bridges, and safety, and for some of the other asset classes in about 60 percent of the states. Nationwide standard practices have been established in a number of areas (e.g., 14 * Million vehicle-miles of travel (MVMT). Outcome Area Area of Analysis LOS Condition LOS Indicator Deficiency Criteria LOS Measures* Safety Statewide, MPO area, non-MPO area Safe travel Traffic fatalities Frequency of traffic fatalities Fatality rate (fatalities/100 MVMT) Traffic crashes Frequency of traffic crashes Crash rate (crashes/MVMT) Table 2-8. Safety state of the practice.

HPMS, NBI, traffic control devices per the Manual on Uni- form Traffic Control Devices [MUTCD]), and the FARS. 2.5 Conclusion The research team finds that it is feasible to establish an IHS LOS system without placing burdensome data collection requirements on state DOTs, at least for the major asset classes of pavements and bridges and the mobility and safety outcome areas. For some state DOTs, implementation would require new data collection processes for some assets and, in some cases, changes in existing data collection practices. Considerable out- reach and promotion would be required to ensure “buy-in” and the implementation of a successful nationwide LOS framework. Based on the research findings, the research team recom- mends a set of indicators and measures that describe the LOS of IHS assets, as detailed in the remainder of this report. The recommended measures either exist in current data collec- tion systems or can readily be developed to define ratings and thresholds for categorizing IHS asset performance. 15