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

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S U M M A R Y Background The purpose of NCHRP Project 20-74(A) was to develop an approach to measuring lev- els of service of the Interstate Highway System (IHS). The IHS is perhaps the most sig- nificant surface transportation asset in the United States. The predecessor report to this research, NCHRP Project 20-74, states: “It is impossible to overstate the importance of the IHS to global, national, regional, and local area movements of people and goods.” Given its significance, there is a very strong case for measuring IHS performance. NCHRP Project 20-74 was undertaken to develop an asset management approach for the IHS. The initial research was published as NCHRP Report 632: An Asset Management Frame- work for the Interstate Highway System. One essential aspect of asset management is the use of performance measures to quantify the service levels that are being provided. This project, NCHRP Project 20-74(A), Development of Service Levels for the IHS, presents an approach to developing levels of service. Research Objectives The objectives of this research are to develop a standard way to describe the level of service of IHS assets and a process that transportation agencies can use to describe levels of service. The research presents a template that transportation agencies can use to mea- sure the conditions of the IHS in their jurisdictions and a guide for implementing the level of service process. This will be used to communicate levels of service in terms that are meaningful to policymakers and other stakeholders. Agency leaders and managers will use this information to • Communicate critical funding needs to decisionmakers, • Direct resources to problem areas, and • Demonstrate accountability to taxpayers. This work also can provide background for discussions at the national level about IHS performance measurement. Research Approach The research team conducted the analysis under the guidance of the project panel. The research approach involved the following: Development of Levels of Service for the Interstate Highway System 1

2Assess the State of the Practice This research identifies level-of-service indicators and measures that would enable mon- itoring of IHS conditions against national objectives. The team conducted a literature search, using resources from TRB, FHWA, NHTSA, AASHTO, and others. In addition to the literature search, the team had first-hand experience with LOS practices in many state departments of transportation. This knowledge was particularly helpful for assets other than pavements and bridges (e.g., drainage, traffic control devices, and other roadside features), because much of the state-of-the-practice information in these areas is unpublished. Although the terms “service level” and “level of service” are often used interchangeably in practice, the states that have been assessing and rating asset conditions the longest generally use level of service (LOS) as the preferred term. Therefore, level of service, or LOS, is used throughout this report. A great deal of the asset LOS work currently being done by state DOTs, especially for assets other than pavements and bridges, is a component part of their maintenance qual- ity assurance programs. Develop LOS Indicators and Measures The state-of-the-practice research yielded the most widely used LOS indicators and measures. Also, three state DOTs were identified as demonstration states that represented a cross-section of best practices (Florida, Mississippi, and Washington). The recommended LOS approach was applied using available data for these three states. The purpose was to demonstrate the application of LOS measures using actual data and to better understand the issues associated with national implementation. A draft template was developed for each asset type and outcome area. The template showed each asset type, asset element, and description, along with LOS indicator, measure, and rating scale. Develop Final LOS Template and Implementation Guide The research team conducted a workshop in October 2009 to validate the research with the NCHRP panel and representatives from the demonstration states. The LOS template was then finalized, incorporating comments and findings from the workshop. An implementation guide was developed to assist department of transportation officials in developing an imple- mentation plan and to assist users in data collection and application of the LOS template across asset groups and outcome areas. State of the Practice The research revealed a mature existing body of work and work in progress related to LOS and performance measurement for the nation’s highway transportation system. This body of work is summarized and expanded on in two closely related NCHRP reports: NCHRP Report 551: Performance Measures and Targets for Transportation Asset Management, com- pleted in 2006 and NCHRP Report 632: An Asset Management Framework for the Interstate Highway System, completed in 2009. The following summarizes findings regarding the state of the practice: • There is a mature state of the practice in measuring and reporting the operational perfor- mance of transportation systems at the state and regional levels, some of which is applicable

to network-level reporting of IHS LOS. In almost all states, there is system-level measure- ment and reporting of LOS for major assets, as well as mobility and safety performance. • There are well established and improving programs of data collection and reporting that address pavement and bridges as discrete asset classes. The states’ pavement and bridge management systems, including condition assessment and reporting, provide a basis for establishing a national LOS assessment program for the IHS. The national focus is on bridges and pavements under the impetus of national data collection and reporting require- ments, including FHWA requirements for the Highway Performance Monitoring System (HPMS) and the National Bridge Inspection program. • There are a growing number of states that collect and report data on the functional per- formance or maintenance condition of IHS assets other than pavements and bridges. These states have established measurement and reporting programs that address mainte- nance LOS—often referred to as Maintenance Quality Assurance (MQA). MQA is now a widely adopted process with an established state of the practice. Typically, through their MQA processes, states address the functional performance of all assets within the Interstate right of way, including roadside features, drainage systems, and traffic control devices. With some variation in measurement approaches, states measure the LOS of these assets to determine if they are functioning as designed to meet asset preservation, mobility, and safety objectives. There is a growing body of best practice information and experience for these asset types that can provide the basis for a consistent national approach. • For the mobility outcome area, previous research efforts, including NCHRP Projects 20-74, 20-60, and 20-24, concluded that state practices vary widely. Definitions, goal areas, and data collection and analysis techniques create difficulties for meaningful comparison of LOS measures at the national level. Although the state-of-the-practice research did not find much commonality among the states to allow a concise statement of practices, there were sufficient measures and data available to warrant development of a few key LOS indi- cators and measures for mobility. These were mainly related to measures of traffic delays and congestion, including percent of heavily congested travel, percent of on-time arrivals, and volume-to-capacity ratios. • 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 fatalities, injuries, and crashes on the highway system. All state DOTs (or their sister public safety agencies) monitor and report safety performance. NHTSA has standardized the reporting of traffic fatalities through their Fatality Analysis Reporting System (FARS). Safety levels of service in terms of fatalities and fatality rates are already being reported for all public roads, including the IHS. • Demonstration states identified some consistent goals or outcomes for the IHS. These include preservation, mobility, and safety. These goals are particularly well suited for the IHS since the original intent of the system was to provide safe, dependable, high-speed interstate transportation. Level of Service Template The LOS template provides direction to states and other jurisdictions for establishing their own IHS LOS programs. The template offers a national measurement approach for each of the goals/outcomes determined to be feasible at this time: preservation, mobility, and safety. The template specifies the elements to be measured along with their definitions and LOS indicators, measures, and thresholds. Table S-1 illustrates the template. In this case, the outcome is preservation and the asset class is traffic control devices—passive. The “elements” are those aspects of asset to be measured, 3

4such as pavement markings. The “indicators” are the conditions to be measured, while the “measures” quantify the extent to which conditions exist. The “level of service thresholds” present different levels in which the LOS measures can be grouped. The thresholds are repre- sented in two ways: as letter grades that can be understood easily by policymakers and other nontechnical personnel, and as quantified values for transportation professionals and other technical audiences. The actual measured condition for each element can be plotted on this scale to clearly present the LOS currently being provided by the IHS. Implementation Guide The Implementation Plan and User Guide will assist agencies in developing and implement- ing their IHS LOS processes. The Implementation Plan will help administrators responsible for agency asset management while the User Guide is intended for those who will oversee the day-to-day LOS assessment process. Goal/Out- come Asset Class Element Definition Indicators Measure Level of Service Thresholds A B C D F Preservation Traffic Control Devices— Passive Pavement Markings/ Symbols/ Legends This element includes any pavement markings, other than line striping, such as exit-lane and through-lane arrows, route numbers, and symbols. Faded, missing. % of elements deficient. 0 - 4.9 5.0 - 9.9 10.0 - 14.9 15.0 -19.9 ≥ 20 Raised Pavement Markers This element consists of reflective devices placed on the pavement to mark travel lanes and pavement edges, as well as ramp lanes and gore areas. Non-reflective/ missing/ damaged. % of elements deficient. 0 - 4.9 5.0 - 9.9 10.0 - 14.9 15.0 -19.9 ≥ 20 Signs This element consists of all types of traffic signs, including regulatory and warning signs, guide and informational signs, regardless of the type of mounting (roadside posts, overhead sign structures, or attached to bridge structures). Non-reflective/ missing/ damaged. % of elements deficient. 0 - 4.9 5.0 - 9.9 10.0 - 14.9 15.0 -19.9 ≥ 20 Table S-1. Illustration of LOS template.

Implementation Considerations There are a number of important considerations in developing an effective IHS LOS pro- gram. These include the frequency of LOS surveys, data collection, using a pass/fail versus a quantitative approach, data weighting, aggregation of measures, and implementation issues. Appendices IHS LOS measurement is complex, requiring considerable research and analysis. Practition- ers developing such measures will benefit from the detail in the appendices (provided on the accompanying CD-ROM) on the IHS measurement state of the practice and the analysis of specific goal/outcome areas and assets. 5