U.S. Department of Transportation
Federal Highway Administration
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A high-level process illustrating the three major steps to incorporating safety performance measures into transportation planning is shown in Figure 1 below. For States and metropolitan areas already using safety performance measures, these steps can help identify new measures and/or enhance existing ones. If performance measures are not currently used, these steps can help identify, select, and incorporate them into the transportation planning process.
Figure 1. Transportation Safety Planning Performance Measures
Safety performance measures originate from many sources, including current goals and objectives, safety data analysis, legislative and program requirements, decision-makers, stakeholders, and other constituencies (see Figure 2).
Figure 2. Sources of Candidate Safety Performance Measures
A typical transportation planning process includes a set of goals and objectives that reflect the values and desires of the community. These goals and objectives provide guidance to transportation officials and analysts, and highlight the types of information required to measure progress toward achieving them. Most State and regional planning processes have goals related to system preservation, mobility and congestion, economic development, safety, environmental quality, and financial responsibility. Developing safety performance measures and aligning them with the planning goals and objectives help decision-makers design and implement strategies and projects that support the community's values.
Figure 3. Sample SHSP Performance Measures
Safety-related goals can originate from within the transportation planning process or be brought into the process from other state or regional safety planning efforts. Strategic Highway Safety Plans (SHSP) include many safety-related goals that lead to performance measures such as those listed in the Figure 3. The SHSP is a data-driven, comprehensive, multidisciplinary strategic plan developed in collaboration with Federal, State, local, and private sector safety stakeholders. It identifies priorities and drives investment decisions by establishing statewide safety goals, objectives, and emphasis areas. As a part of the SHSP process some States have developed performance measures to further guide safety improvement efforts. Additional safety-related goals and information can be drawn from other safety plans and programs, such as the Highway Safety Improvement Program, Highway Safety Plan, and/or Commercial Vehicle Safety Plan.
Most transportation planning efforts begin with a preliminary analysis of the challenges facing the system. In almost all cases, this ongoing effort continually identifies new issues and feeds them into the planning process. For example, regional planning analysts often conduct corridor studies that provide details on the types of challenges and system deficiencies found in a portion of the region. Improving overall transportation safety within the corridor is almost always a major goal of such studies. Data analyses focus on identifying intersections and other high-crash locations in the corridor, followed by more detailed investigation of the types of strategies that can be used to reduce crashes. Corridor studies suggest strategies and recommend projects for the long-range transportation plan and for the S/TIP program.
Figure 4. Southeast Michigan Council of Governments Safety Performance Indicators
Monitoring of transportation safety problems (e.g., run-off-the-road crashes, alcohol-related crashes, pedestrian/bicycle crashes, and transit incidents, etc.) results in collection and analysis of data useful for developing performance indicators such as those in Figure 4. The SHSP development and associated update activities also provide potentially valuable data about the safety challenges facing a state. For example, SHSP contain emphasis areas (e.g., lane departures, intersections, occupant protection, etc.) identified through the data analysis. The emphasis areas, and the analyses associated with them, provide a rich data source for the development of safety performance measures. Similar analyses from other safety programs and plans, such as the highway safety improvement program, can serve the same purpose.
Transportation planning stakeholders often identify safety issues critical to their interests. For example, Mothers Against Drunk Driving, AAA, pedestrian and bicycling advocacy groups, the trucking industry, and the public health/medical establishment are interested in transportation safety issues specific to their missions. Transportation officials might consider developing safety performance measures that align with major public safety issues and with the concerns of important interest groups. For example, performance measures could be used to monitor the proportion of all fatalities involving lane departures, impaired drivers, or commercial motor vehicles.
Sometimes transportation officials develop safety performance measures in response to legislative, regulatory or other higher authority requirements, such as the NHTSA/GHSA requirements referenced in Table 1. Such requirements will likely increase as government programs become more performance-oriented with a greater concern for transparency to the public.
People who make investment or operational decisions and establish laws or policies might identify the information required to make better decisions in the future. Indeed, one of the original motivations for developing transportation performance measures was the state legislature's desire to know the benefits of transportation investments and expenditures. Some commonly used information include the following: data on the safety of the transportation system (e.g., fatalities, injuries, or crashes); results of targeted initiatives (e.g., the reduction in crashes after installation of traffic signal upgrades or the number of driving under the influence (DUI) arrests or crashes where alcohol was a factor following an impaired driving program), and data on the safety concerns of interest to key constituencies (e.g., fatalities and injuries to young drivers or pedestrians). Decision-makers also focus on output measures such as the number of citations issued, number of road miles with guardrails, or the number of high-crash sites that received treatment. These types of performance measure-based information are the foundation of a transparent and accountable policy-making process.
A process for selecting candidate safety performance measures is shown in Figure 5 below. It recognizes that the most important issue transportation agencies face when considering candidate performance measures is data availability.
Figure 5. Selecting Safety Performance Measures for the Transportation Planning Process
The candidate performance measures identified in the previous section are reviewed and examined as follows:
While the selection of safety performance measures is described as a sequential process, in reality all performance measures will likely be reviewed at the same time. After the candidate safety performance measures have been considered, those that are selected need to be incorporated into the transportation planning process.
The question should always be asked, “Are sufficient data available to support a candidate safety performance measure?” Experience has shown that performance measures are often selected based on their appeal as “good information to have,” only to discover that the necessary data do not exist and/or that data collection is prohibitively expensive. This initial step simply determines if data resources are currently available to support the performance measure. Such a determination relies on interaction with the data collection and processing units within the responsible agencies.
Often, the required data are collected by various agencies for a variety of purposes. Transportation planners should build the necessary relationships to enable them to access and use the data sources to measure transportation safety performance.
The NHTSA has identified six core data systems for use in a highway safety performance measurement system (Source 8):
Some of these systems are more obviously related to the transportation planning process, such as crash and roadway data systems, than others are. While the level of relevance varies depending on the priorities of a given agency, each of these systems generates useful data for highway safety performance measurement.
For transit, the most frequently-used types of data include ridership (broken down by demographics), vehicle and passenger miles traveled, and number of trips. To estimate crash risk for example, one might use measures such as 0.24 injuries per 100 million passenger miles traveled or 0.15 injuries per 100,000 riders.
The most commonly used safety data source for transportation planning is a crash data management system. It provides the time, location, environment, characteristics, and contributing crash factors, such as obstructed view, alcohol impaired driver or pedestrian, red light running, etc. Crash information should link to other sources of information as well, (i.e., roadway inventory, driver history, etc.) and provide details on the roadway, vehicles, and people involved in the crash. Crash consequences, such as fatalities, injuries, property damage, and traffic violations are also available through the crash data management system.
Crash data can be used for analysis of a single crash or aggregated for statewide, regional, or corridor planning. A State crash data system should accommodate information on all reportable motor vehicle crashes on any public roadway. In most States, a Traffic Records Coordinating Committee (TRCC) or Traffic Records Committee provides oversight and guidance for developing consistent traffic safety records. The TRCC is helpful for coordinating the many different safety-related data collection and data management activities in a State. If not already involved, transportation planners are encouraged to work with their State TRCC.
The results of a recent survey of State DOTs and MPOs on the types of safety data used in transportation planning are shown in Table 2. Not surprisingly, vehicle crashes, vehicle miles traveled, and roadway characteristics are in the top five for both State DOTs and MPOs. Pedestrian crashes also are highly ranked. Rail crashes are in the top five for State DOTs because of their special responsibility for highway/railroad grade crossing safety programs, particularly in rural areas.
|Data Source||MPO||State DOT|
|Vehicle miles traveled||2||4|
|Air transport crashes||9||10 (tie)|
|Transit/paratransit incidents||10 (tie)||10 (tie)|
|Water navigation crashes||10 (tie)||15|
|Safety belt/restraint use data||12||14|
|Emergency medical response||13||16|
If data to support a safety performance measure are available, a strategy for systematic data collection over time must exist. Such strategies require that data collection schedules, organizational roles and responsibilities, needed resource allocations, and data collection methodologies are incorporated into the standard procedures of the implementing agencies. Importantly, a careful examination of the collection strategy should be made to assure the data meet the quality standards and schedule needs to support the safety performance measures. The following characteristics, identified by NHTSA (Source 8), are critical data collection factors for consideration as part of an overall data management strategy:
Other characteristics of performance measures to consider include (Source 8):
Although transportation planning is performed in numerous jurisdictions for a variety of reasons, several elements of the planning process are common among them. Figure 6 below outlines the general transportation planning process from developing vision and goals to monitoring system performance (Source 9). The figure shows that linkages between safety performance measures and the transportation planning process exist for each element.
Incorporating safety performance measures into a transportation plan's vision, goals, and objectives leads to the implementation of more projects with safety components and benefits. This is primarily because integrating performance measures in this initial step results in subsequent planning steps also doing so (e.g., use of safety criteria in project evaluation). A community's transportation vision and corresponding goals and objectives should have a strong, two-way linkage to safety through the establishment of performance measures. Safety performance measures that support the plan's goals and objectives are then aligned with what decision-makers, stakeholders and others in the community value. Another benefit of incorporating safety into the visioning process is that those involved become aware of safety's importance, which is instrumental in building constituencies to support safety projects through the remaining planning steps.
Linking safety performance measures to the identification of improvement strategies can lead to the implementation of projects and strategies that save lives and reduce safety-related economic costs to society. For example, performance measures that focus on reducing pedestrian-vehicle crashes could encourage the development of programs to identify and improve locations where such crashes are likely to occur. Likewise, performance measures that focus on lane departure crashes can lead to programs to reduce their occurrence and limit their severity. Strategies developed in response to robust safety-related performance measures can be either operations-oriented (e.g., improving incident management programs or using intelligent transportation systems to monitor crash occurrences), infrastructure-oriented (e.g., implementing a “hot-spot” program to improve geometric designs at high crash locations or improving transit station configurations to reduce vehicle-pedestrian conflicts), or both.
Figure 6. Relating Safety Performance Measures to Individual Steps in the Transportation Planning Process
Properly designed safety performance measures are essential to the evaluation and prioritization of strategies. This is where improving safety takes its rightful place next to the other planning considerations (e.g., system preservation, improving accessibility, reducing congestion, etc.). The planning process estimates the relative effectiveness of various strategies and prioritizes capital and maintenance investments based on evaluation criteria. Effective safety performance measures lead to safety-related evaluation criteria. For example, if “number of crashes” is a safety performance measure, it would be important to evaluate proposed projects and strategies from the perspective of their impact on the number of crashes. The benefit of linking safety performance measures to the evaluation and prioritization step is that more safety-related projects will emerge from the planning process. This will ultimately lead to a reduction in the number of crashes and fatalities.
The use of safety performance measures throughout the planning process will lead to the selection of more projects and strategies with safety benefits. Given that the Long-Range Plan (LRP) represents a strategic perspective on the future of the State or regional transportation system, incorporating safety into the LRP, through the use of safety performance measures, ultimately leads to reductions in crashes and fatalities.
The linkage between performance measures and S/TIP adoption is one of the most crucial in the transportation planning process. Having strong safety performance measures leads to the development of prioritization criteria that include safety and result in more safety-related projects being selected for the S/TIP. For example, the Denver Regional Council of Governments (DRCOG) applies more weight, or safety points, to roadway improvements that have higher crash reduction potential (see Figure 7). This results in a capital program for a State or region that includes projects that reduce the number and severity of crashes. If decision-makers want a greater emphasis on one type of project over another (e.g., those having a greater impact on system safety), assigning greater weight to the related prioritization criteria is one way to do so.
To the extent that it is identified as a planning concern and incorporated into the planning process, safety will have a role in detailed project analysis. The project development step examines specific engineering and environmental details in designing and preparing a project for construction. Depending on the size and expected significance of environmental impacts, the project development process may also entail substantial environmental analysis. Safety performance measures provide additional guidance on the types of designs and operational strategies that should be considered as part of the project design (e.g., median barriers to reduce cross lane crashes, reflective signage, sidewalks and bike paths, or construction work zone safety initiatives).
The impact of safety performance measures in this step can be identified by the manner in which projects and strategies are implemented. An emphasis on safety in program implementation may be reflected in safety conscious land use and urban design standards; enhanced safety design standards; improved safety operational strategies for vehicles (i.e., congestion), pedestrians, and bicyclists; and work zone safety programs.
The benefit of including safety performance measures as part of a system monitoring program is that safety
issues are identified earlier and addressed as part of the planning process, leading to the adoption of strategies or the implementation of projects that will improve the safety performance of the transportation system. This early identification of safety challenges and eventual solutions can result in implementation savings in that investments can be made before the safety challenge reaches a point where higher levels of resources would be necessary.
Ongoing monitoring of system performance provides data and information that should be fed back into the goals and performance measures. A well designed monitoring process can indicate where and when course corrections are needed to improve safety performance. System monitoring consists of the traffic surveillance, traffic counting, transit ridership, review of traffic records databases (including crash data), and other means of determining the performance of the transportation system. Monitoring is done by a variety of agencies and the results are incorporated back into the planning process.
Accurately measuring the impact of implemented actions benefits the planning process and decision makers in that both become aware of what types of safety projects, strategies, and countermeasures are most cost effective. This permits decision-makers to target their limited resources on those projects and strategies that are likely to result in the greatest reduction in crashes and fatalities. The post-implementation evaluation or assessment process helps determine the effectiveness of such countermeasures. Without it, no information is available to assess the actual benefit of the countermeasure and justify its future use. Funds should be set aside to allow a proper, scientific evaluation of the countermeasures whenever possible. A proper evaluation considers other variables that could have an effect on the number and/or severity of crashes, such as changes in the number of vehicles using the corridor (e.g., exposure), changes in demographics (proportion of older or younger drivers in the area), etc. While transportation planners do not perform the evaluations themselves, they should be kept informed of the results.
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