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FHWA Home / Safety / Intersection / Strategic Intersection Safety Program Guide

Strategic Intersection Safety Program Guide

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Publication No. FHWA-SA-09-004

FHWA Contact: Lawrence J. Brown, HSSD, 202-366-2214

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3. Strategic Intersection Safety Program Process

The strategic process for development, implementation, and evaluation of strategic intersection safety programs described in this section can be useful and applicable whether the program will be included in a statewide safety plan, such as an SHSP, or in a plan for a specific local jurisdiction.

Figure 7 illustrates the strategic process developing for an intersection safety program. The "Process Decisions/Determinations," shown in the first column of Figure 7, represent the major steps in the process. These steps are individually described as Steps A through L in this section of the guide. These process steps are associated with "Related Documents" and "Supporting Actions" identified in the center and right columns of Figure 7, respectively. The process shown in Figure 7 and described below is applicable to the development of any highway safety program, including an SHSP, but additional details relevant to intersection safety are presented as illustrations for this guide. Applying this SHSP-based process will help assure that the resulting intersection programs are compatible with the State's SHSP and that the planning process considers the various road safety improvements that may affect the State's strategic goals.

While Figure 7 shows each step in a particular order, it is important to recognize the iterative nature of the process, especially the steps involving the development of intersection safety action plans (Steps E through I). These steps may be reordered based on agency priorities, available resources, or the decisions made in other steps of the process. For example, the step in which strategies and countermeasures are chosen is shown prior to the step in which sites for implementation of these strategies and countermeasures are identified. This order was chosen to encourage agencies to select treatments based on needs identified from their data. However, once specific improvement sites are selected and studied, the specific list of strategies and countermeasures to be implemented may need to be reconsidered to fit the safety improvement needs of those specific sites. In addition, while performance-based goals are initially set prior to the selection of strategies and countermeasures, these goals may need to be modified to fit realistic expectations of crash reductions that will be provided by those countermeasures. The steps in the process have been given letters, rather than numbers, so as not to suggest an inflexible sequence.

Figure 7 illustrates the process for developing an intersection safety program in three columns.  Column 1, “Process Decisions/Determinations”, identifies the 12 steps of developing an intersection safety program.  The second column, “Related Documents”, names the documents that correspond to the steps in Column 1.  The third column, “Supporting Actions”, identifies a supporting action for each of the steps in Column 1.
Figure 7. Process for Developing an Intersection Safety Program

Step A-Identify Key Stakeholders

An initial step in developing an intersection safety program is to identify key stakeholders and to bring them together in a task force or working group. This initial step requires managerial support and inclusion of participants with a diverse knowledge of intersection safety issues, including each of the "4Es": engineering, enforcement, education, and EMS. This helps assure that the intersection safety program can be appropriately developed, implemented, and coordinated, and that it will be comprehensive in nature.

Figure 8 shows a photo of a stakeholder group.  The photo includes eight stakeholder participants, including a highway patrol officer.
Figure 8. Stakeholder Group

A Stakeholder Group Should Include Representatives From Each of the 4Es—Engineering, Enforcement,
Education, and EMS

The support activities should include:

Potential Data Sources

  • Crash records maintained by agencies within the jurisdiction or by the State
  • State SHSP
  • Intersection inventory data
  • Speed data
  • Driver records (e.g., enforcement, licensing, courts)
  • EMS or trauma center data

It is helpful to designate a diverse group of motivated partners and stakeholders that understand the importance of intersection safety and represent each of the 4Es. Personnel with experience in collecting, managing, and analyzing safety data should be included.

Step B-Identify Intersection Safety Needs

An important step in setting the proper direction for an intersection safety program is to analyze the best and most complete data available on the safety performance of intersections in the jurisdiction. This provides legitimacy for the goal-setting process and gives confidence that the key intersection safety issues are being addressed.

A preliminary analysis of intersection safety data and information is helpful in seeking initial managerial support. Such an analysis can identify the magnitude of intersection safety needs in the jurisdiction and the extent to which intersection safety should be a priority. This analysis should be based primarily on crash records. Definitions of key crash-related terms include:

Police Crash Reports

Crash reports provide an abundance of information for the analyst. While individual crash reports are important resources for an analyst investigating an individual intersection’s safety needs and strategies, collections of such crash records are useful for evaluating system-wide intersection safety concerns, trends and needs.

Crash reports are a primary resource for safety analysis, providing the data and information needed for safety-related analyses such as driver and vehicle characteristics, weather and roadway conditions, and location information related to intersection crashes. Most crash reports also include a collision diagram, which can further help the analyst understand the sequence of events leading to crashes and provide insights into the safety issues that may need to be addressed in an intersection program.

Searchable electronic databases of crash reports allows the data analyst to more quickly and efficiently determine trend information such as the percentage of crashes that are occurring at intersections, the proportion of specific crash types to total crashes, and the prevalence of certain crash characteristics (e.g., alcohol involvement, speeding, age of driver, failure to obey traffic control devices).

Figure 9 shows a sample police crash report.  The sample crash report is blank (not yet completed), but includes spaces for entering information about the driver, vehicle, and roadway.
Figure 9. Section of a Sample Police Crash Report Form

Consider supplementing data with local knowledge, such as:

  • Local law enforcement
  • State traffic and maintenance engineers
  • Local engineering staff
  • Local residents and road users

Once a decision is made by the stakeholder group to initiate an intersection safety program or an intersection emphasis area within a safety plan, a more in-depth analysis of intersection safety data and information should be conducted to identify specific intersection safety needs that may be addressed by countermeasures. Identification of needs should be based on this data-driven process and on the experience and knowledge available to the stakeholder group.

Intersection safety data and related information, such as traffic volumes, may be available from State agencies as well as local jurisdictions. The stakeholders may have various crash databases created by their own agencies or derived from State-level data. The stakeholder group should attempt to review, if available, intersection crash frequencies, severities, patterns, types, and locations to determine safety needs. The collection, reporting, and availability of crash data is continuously improving as a result of data improvement projects and technologies, which in turn improve the quantitative identification of safety needs. State SHSPs are based on statewide safety data analyses and should be considered a resource for any development of intersection safety programs at the State and local level.

In most States, a State agency such as the Department of Motor Vehicles or the Department of Transportation maintains records of intersection crashes. In many cases, however, location-based crash data is only available for the State-maintained highway system. The completeness of available crash data for intersections on local road systems varies widely by jurisdiction. A key data limitation in many jurisdictions is the lack of accurate location data for crashes, which can affect the accuracy of determining which intersections have the greatest needs. For example, a crash that is reported as being even 100 feet away from where it actually happened may be attributed to conditions (such as road design, lighting, or traffic control) that are different from those at the actual crash site.

Other sources of information that may be considered include:

  • Speed data
  • Interagency agreements
  • Driver records
  • Safety audits
  • EMS/trauma center data
  • Identified high-crash locations
  • Existing plans and programs
  • Motorist complaints

A review of the "4E" efforts currently devoted to intersection safety in the jurisdiction should be performed. Crash types and patterns are strongly influenced by such items as intersection design, traffic control, levels of enforcement, and education campaigns. Fatality rates may be influenced by the timeliness of EMS arrival, particularly at rural intersections. Thus, it is most useful to have an intersection inventory that could be referenced when identifying safety needs, including items such as:

If not included in an inventory database or otherwise readily available, data on intersection characteristics may be obtained through a review of crash databases or copies of police crash reports.

Step C-Adopt Strategic Intersection Safety Goals

A strategic intersection safety goal is a target that establishes a direction and focus for efforts to improve safety at intersections.

Strategic goals are long-term goals that provide a direction and focus for present and future intersection safety improvement efforts. This step establishes high-level strategic goals for improving intersection safety over a specified period of time. An example strategic goal may be to reduce the current number of intersection fatalities by 15 percent over the next five years. While the SHSP sets statewide strategic goals for overall highway safety improvement, some States adopt strategic goals for specific emphasis areas, such as intersection safety, in their SHSP (shown previously in Table 2). Setting clear strategic goals is critical to the development of a successful intersection safety program. Strategic goals help define the scope of improvements to be considered and are used to help measure the success of program implementation. Later, they can help establish the need for changes in future projects, improvement strategies, implementation approaches, and goals.

Development, adoption, or recommendation of strategic goals for an intersection safety program may be the responsibility of the stakeholders involved, but also may be mandated by legislation, decision-makers, and/or other strategic plans or policies.

Key considerations for establishing a meaningful strategic goal for an intersection safety program include:

The following are a few examples of strategic goals that could support an overall intersection safety program or an SHSP intersection emphasis area:

Goal-Setting Tips
  • The strategic intersection safety goal should be challenging, but achievable.
  • Goal setting is often an iterative process; as measures of effectiveness from the implemented projects and programs become available, expected reductions in crashes can be better defined.
  • Goal setting requires a continuous balancing of intersection safety needs and available funding.

After the strategic goals for an intersection safety program have gained consensus and approval from leadership, they should be reflected in other transportation plans, including any future updates of the SHSP.

Step D-Identify Intersection Safety Action Plans Needed

Intersection safety action plans (sometimes called implementation plans) are used to coordinate, define, and implement the various projects needed to achieve an intersection safety program's strategic goals. A strategic intersection safety program may need one or several intersection safety action plans. It may be most effective to address different categories or types of intersections, crashes, or projects. For example, an agency might choose to develop separate action plans for signalized and unsignalized intersections. In this step, the stakeholder group must determine which intersection or crash types may benefit from their own action plan.

For a few States, the intersection emphasis area of the SHSP is comprehensive enough to serve as an intersection safety action plan. However, most SHSPs provide a broad overview of intersection needs and strategies, and should be supported by more detailed action plans. These action plans should be guided by the goals and priorities outlined in the SHSP. A benefit of developing action plans separate from the SHSP intersection emphasis area includes allowing more agile and tailored intersection action plans, updated without the higher-level approvals required for SHSP modifications.

Intersection safety action plans should be developed to have a positive impact on achieving the strategic goals developed in Step C. Action plans are normally developed after the strategic goals are approved to assure they help to achieve these goals. However, preliminary action plans may need to be drafted or developed in parallel with the development of the strategic goals to ensure their likelihood of being accepted or to achieve a desired outcome for the overall intersection safety program.

Steps E through K, presented below, describe the process of developing the intersection safety action plan(s) chosen by the stakeholder group. In summary, these steps describe the process of:

These steps describe the basic elements of developing an intersection safety action plan; however, they are not rigidly defined, and in practice, they will likely be iterative. For example, once implementation sites have been selected, the strategies and countermeasures chosen previously may be reevaluated for appropriateness for the sites chosen. Also, performance-based goals that are originally based on the needs defined during the initial data analysis may be revised after specific countermeasures and sites are chosen in order to ensure that the performance-based goals are realistically achievable.

A sample intersection safety action plan is available from FHWA.(13)

Step E-Develop Intersection Performance-Based Goals

Intersection performance-based goals are shorter-term goals that contribute toward achieving the intersection strategic goals and may address only one portion of the intersection safety program. For an intersection safety program, performance-based goals are a reflection of anticipated improvements in safety intended to be achieved with a specific action plan. Intersection improvement strategies and countermeasures and specific improvement sites will be selected in subsequent steps to achieve these performance-based goals. The performance-based goals are intended to be achieved by implementation of the intersection safety action plans, and may be applicable to the same time period or a shorter time period than the overall strategic intersection safety goals.

In developing performance-based goals for an intersection safety action plan, the selected goals should:

Examples of intersection performance-based goals include:

Current practice for many States is to set their performance-based goals at yearly intervals measured over the life of the strategic intersection safety program. Intersection stakeholder groups should establish performance-based goals related to current safety measures, conditions, and activities to assess progress over the period of the strategic intersection safety plan or SHSP safety goals.

Step F-Select Intersection Safety Improvement Strategies and Countermeasures

The intersection performance-based goals developed in the previous step address specific intersection improvement needs or target crash types (e.g., right-angle crashes, red-light running crashes, crashes involving older drivers) identified as concerns by a highway agency. In this step, the stakeholder group selects improvement strategies and countermeasures to address the target intersection and crash types. An intersection improvement strategy is a treatment or method for improving safety at intersections. Each strategy includes one or more countermeasures that typically address a particular intersection feature or a particular safety need. Each countermeasure is a specific improvement that can be made or a specific action that can be taken at an intersection to reduce the number of crashes of a specific target crash type. Countermeasures are the specific actions taken to implement intersection improvement strategies. Countermeasures include physical improvements such as changes to the roadway geometry (e.g., alignment and cross section) and traffic control improvements. Actions such as targeted enforcement for speeding or red-light running, educational campaigns, and improvement in emergency medical services (EMS) coordination, are also considered countermeasures.

Figure 10 shows the cover of NCHRP Report 500, Volume 12, A Guide for Reducing Collisions at Signalized Intersections.
Figure 10. Cover of
NCHRP Report 500

Several resources are available to assist highway agencies in selecting appropriate strategies and countermeasures for improving safety at intersections. These include:

Volumes 5 and 12 of the NCHRP Report 500 guides present comprehensive lists of strategies and countermeasures for improving safety at intersections. These guides address engineering, education, and enforcement strategies and countermeasures. A related guide in Volume 15 of the NCHRP Report 500 series presents strategies for improving EMS,(20) and guides for speed reduction on low- and high-speed facilities are under development.

Using these resources in combination with local knowledge of successful strategies, highway agencies should develop a list of promising improvement strategies that should be considered for inclusion in the intersection safety action plan. Strategies should be identified as "promising" if they address the specific intersection priority needs and performance-based goals that have been developed.

Figure 11 shows the SAFETEA-LU logo.  The logo consists of a teal blue box with white lettering that says “SAFETEA-LU; Safety Accountable Flexible Efficient Transportation Equity Act: A Legacy for Users”.
11.  SAFETEA-LU Logo

In addition to selecting improvement strategies and countermeasures that address existing intersection crash patterns, improvements that minimize road hazards may be considered. This approach is illustrated in the Federal "Safe, Accountable, Flexible, Efficient Transportation Equity Act: A Legacy for Users" (SAFETEA-LU), which requires States, as part of the SHSP, to identify opportunities to minimize hazardous road conditions and to establish a schedule of safety projects for crash prevention. A prevention approach provides an opportunity for the intersection safety program to be proactive in providing strategies and countermeasures that address potential intersection safety concerns or potential intersection safety concerns crash patterns before they develop.

As an example, the signalized intersection guide presented in Volume 12 of NCHRP Report 500(8) lists the strategy Revise Geometry of Complex Intersections; this strategy consists of several countermeasures, including:
  • Convert a four-leg intersection to two T-intersections
  • Convert two T-intersections to one four-leg intersection
  • Improve intersection skew angle
  • Remove deflection in through-vehicle path
  • Close intersection leg

The selection of appropriate strategies and countermeasures (also encouraged in SAFETEA-LU) should consider input from representatives of the 4Es; engineering, enforcement, education, and EMS. The stakeholder group formed in Step A of the strategic intersection safety program process may serve this purpose. A combination of strategies and countermeasures from each of the 4Es should be thoughtfully considered in the intersection safety action plans.

Once promising strategies have been identified, the stakeholder group must choose specific countermeasures to implement the chosen strategies. Some of the strategies identified can be addressed with a single countermeasure, while other strategies may be best implemented with multiple countermeasures.

FHWA has recently published a Desktop Reference for Crash Reduction Factors, (21) which can help an agency evaluate the potential effectiveness of particular strategies or countermeasures. A crash reduction factor (CRF) is the percentage crash reduction that might be expected from implementing a given countermeasure. The Desktop Reference presents estimates of the crash reduction that might be expected at an intersection if a specific countermeasure, or group of countermeasures, is implemented at the intersection. While the Desktop Reference only includes countermeasures for which CRFs have been quantified, it may also serve as a useful resource to highway agencies in identifying appropriate intersection countermeasures. FHWA has published other documents based on the Desktop Reference that are useful resources as well, including:

NCHRP Report 617, Accident Modification Factors for Traffic Engineering and ITS Improvements,(23) also provides estimates of the safety impacts of various countermeasures, including intersection treatments.

In addition to evaluating potential effectiveness of strategies and countermeasures, consideration should be given to feasibility (political, financial, social acceptance, etc.), and to practicality (such as choosing countermeasures that do not violate driver expectancy for the region or that can be implemented in local conditions). Countermeasure selection must also consider applicable agency policies, State laws, and other institutional constraints.

A majority of States have identified intersection-related strategies and/or countermeasures in their SHSPs. The strategies and countermeasures found in the current SHSPs for each State are provided in Tables 4 through 8 as a resource for agencies in choosing appropriate strategies and countermeasures.

Table 4. Intersection-Related Strategy Categories
Intersection-related strategy categories Number of SHSPs Percent of all SHSPs
Traffic control strategies 40 78.4
Geometric design strategies 37 72.5
Additional engineering strategies 44 86.3
Education strategies 25 49.0
Enforcement strategies 37 72.5
EMS strategies 6 11.8

Table 5. Intersection Traffic Control Strategies and Countermeasures Included in SHS
Traffic control strategies and countermeasures Number of SHSPs Percent of SHSPs with
intersection-related strategies*
Improve visibility of signing and marking 25 53.2
Improve/update signal timing 17 36.2
Add phasing/protected left-turn phases 15 31.9
Add pedestrian signals/countdown signals 14 29.8
Signal head improvements (larger, LEDs, backplates) 12 25.5
Add/improve signal coordination 11 23.4
Optimize clearance intervals 9 19.1
Provide better guidance/delineation 9 19.1
Install flashing beacons on stop signs or overhead
at stop-controlled intersections
7 14.9
Prohibit right turn on red 7 14.9
Add supplementary signs and markings 6 12.8
Add/improve pedestrian phasing 5 10.6
Provide stop bar 5 10.6
Add vehicle detection devices on approaches for dilemma zone 3 6.4
Install or remove signals according to MUTCD warrants 3 6.4
*Based on the 47 SHSPs that included at least one intersection-related strategy.

Table 6. Intersection Geometric Design Strategies and Countermeasures Included in SHSPs
Geometric design strategies and countermeasures Number of SHSPs Percent of submitted SHSPs with
intersection-related strategies*
Improve sight distance/clear sight triangles 22 46.8
Improve pedestrian crossings 21 44.7
Add, offset, or lengthen left-turn lanes 20 42.6
Provide/consider roundabouts 19 40.4
Add, offset, or lengthen right-turn lanes 12 25.5
Provide channelization 9 19.1
Add turn restrictions/indirect left-turn treatments 7 14.9
Provide acceleration lanes 6 12.8
Reduce intersection skew 6 12.8
Build bypass lanes at T-intersections 3 6.4
Change 4-leg intersection to two offset 3-leg
intersections/one-way pairs
3 6.4
Provide deceleration lanes 2 4.3
*Based on the 47 SHSPs that included at least one intersection-related strategy.

Table 7. Additional Intersection-Related Engineering Strategies and Countermeasures Included in SHSPs
Additional engineering strategies and countermeasures Number of SHSPs Percent of submitted SHSPs with
intersection-related strategies*
Provide better access management near intersections 24 51.1
Provide or improve intersection lighting 21 44.7
Identify, prioritize, and track improvements at high-crash locations 20 42.6
Install active control devices at rail-highway grade crossings 13 27.7
Provide advance warning signs/flashers 13 27.7
Conduct intersection safety audits 10 21.3
Install transverse rumble strips on intersection approaches 10 21.3
Employ ITS and/or new technologies 9 19.1
Improve data collection, sharing, and analysis 8 17.0
Install advance street name signs 6 12.8
Install dynamic warning signs/flashers 6 12.8
Eliminate parking near intersections 4 8.5
Improve intersection planning and design policies 4 8.5
Post approach intersection speeds (regulatory or advisory) 4 8.5
*Based on the 47 SHSPs that included at least one intersection-related strategy.

Table 8. Intersection-Related Education, Enforcement, and EMS Strategies Included in SHSPs
Education, enforcement, and EMS strategies Number of SHSPs Percent of submitted SHSPs with
intersection-related strategies*
EDUCATION STRATEGIES 25 53.2
Educate users about high-crash locations / safety issues 8 17.0
Educate users about intersection traffic controls 8 17.0
Educate designers about safety improvements 5 10.6
Educate drivers about gap acceptance 4 8.5
Educate consultants and developers about access management 2 4.3
ENFORCEMENT STRATEGIES 37 78.7
Provide automated red-light enforcement 27 58.4
Provide targeted law enforcement at intersections 23 48.9
EMS STRATEGIES 6 12.8
Provide signal preemption for emergency vehicles 6 12.8
*Based on the 47 SHSPs that included at least one intersection-related strategy.

Step G-Determine Implementation Priorities

This step develops priorities for implementation of the selected intersection improvement strategies and countermeasures. The following should be considered when determining implementation priorities:

Highway agencies should not overlook local experience with a particular strategy in deciding which strategies to use in their action plans. If a strategy has been successful in improving safety at one location, it should be considered for implementation at other locations.

Priorities may be based on quantitative analysis, such as benefit-cost or cost-effectiveness analyses. At this stage, analyses should consider safety performance for typical intersections, but need not consider specific intersection sites.

Step H-Select Candidate Sites

This step involves the selection of candidate sites for intersection improvements based on implementation priorities and the crash history or future expected safety performance of specific intersections. This step applies primarily to engineering and enforcement improvements. Education and EMS strategies are more typically area-wide or systemwide in nature and are not generally targeted at specific sites.

As part of the development of an intersection safety action plan, the participating highway agencies should consider the specific intersections at which engineering improvements or enforcement activities should be implemented. The list of improvement sites may include known high-crash locations, but may also include other locations with crash patterns that may be addressed with specific strategies or countermeasures.

Many highway agencies have developed software tools for screening the highway network to identify candidate improvement sites. The NCHRP Report 500, Volume 21, Guide for Addressing Safety Data and Analysis in Developing Emphasis Area Plans(24) includes a chapter on intersection safety that suggests how crash data can be analyzed to identify candidate improvement locations. The primary procedure in the above guide describes procedures for the analysis of high-quality intersection databases that include:

Alternative procedures for selecting candidate sites are also provided in the NCHRP Report 500 guide for application to less complete data sets in which the crashes are not accurately referenced to a milepost or when an intersection inventory file is not available.

Figure 12 shows the SafetyAnalyst logo. The logo consists of a white box with red lettering that says “SafetyAnalyst”.  There are three red boxes above the word “Safety”.
Figure 12. SafetyAnalyst Logo

The FHWA SafetyAnalyst software,(25) planned for release in 2009, will provide analytical tools to help highway agencies identify candidate improvement sites and determine appropriate countermeasures.

One tool under consideration for the SafetyAnalyst software will enable a user to choose a particular countermeasure and identify sites that would be appropriate for implementation of that countermeasure.

Individual highway agencies may also have their own analytical tools for use in identifying candidate improvement sites.

A list of specific intersections to be considered for safety improvements in the intersection safety action plan should be developed. Depending on a number of factors, including the available budget and the cost of the countermeasures selected, it will not necessarily be possible to program safety improvements for all intersections with safety needs. The list of intersections developed in this step and the strategies and countermeasures applied at these intersections should achieve the performance-based goals established for the intersection safety action plan.

A variety of approaches to categorizing and prioritizing safety needs and allocating resources to those needs accordingly may be used when selecting the sites for implementation of the intersection safety action plan. Ideally, resources are allocated so that the projects with the greatest impact on achieving the strategic goals are funded. Each jurisdiction and its planning partners may use any of the following approaches to help make these prioritization and funding decisions:

Step I-Define Intersection Safety Projects

4E projects are defined in this guide to include both the physical infrastructure improvements, which are referred to as projects, as well as enforcement and education efforts, which are often described as programs.

This step defines specific projects that will implement the safety strategies and countermeasures at the candidate intersections as prioritized in the previous steps. Improvement projects may be implemented as stand-alone projects at specific intersections or groups of intersections, such as along a particular corridor. However, the intersection safety improvements may also be provided as a coordinated part of large-scale project involving an intersection. A number of factors should be considered when defining intersection projects, including:

Step J-Identify Appropriate Funding Sources

This step involves the identification of appropriate funding sources for implementation of each project in the intersection safety action plan. A broad range of potential funding sources should be considered and may be combined, including Federal, State, and local funding, as well as private industry and organizational programs.

Potential funding sources from Federal programs for intersection safety projects include:

Potential funding sources from State and local jurisdictions may include grants or other funding specifically designated for highway safety, public safety, public health, or roadway construction or maintenance. Private funding may be available for improving intersection safety through private industry, non-profit organizations, and coalitions that have an interest in improving employee or community safety. Commercial developers often provide funding for intersection safety improvements to mitigate the traffic operational impacts of their developments, such as changing traffic patterns or increased traffic volumes.

Obtaining public funding for intersection safety improvement projects often requires approvals and programming within a government planning process based on Federal, State, and local funding criteria and regulations. For example, Federally-funded road projects would be included in the State Transportation Improvement Program (STIP), and, if in a metropolitan area, included in the Transportation Improvement Program (TIP) that is administered by the metropolitan planning organization (MPO). A strategic intersection safety program developed using the steps in this guide, which follow the typical transportation planning process, can be instrumental in obtaining and coordinating the needed project funding for intersection improvements.

Step K-Implement Funded Projects

This step involves implementing the intersection projects for which funding has been identified. Incremental or staged implementation of the intersection projects may be appropriate when funding is limited or restricted. Staged implementation of engineering/infrastructure improvements typically involves pre-design (e.g., environmental and right-of-way clearances), design, and construction. Staged implementation of enforcement, education, and EMS projects may involve planning (e.g., operations design), pilot projects, and full project execution. Staged implementation of different types of projects at a given location may also be critical to program outcomes. For example, staging a road improvement project prior to an enforcement project may allow engineers to incorporate traffic control devices that may assist law enforcement officers in their efforts.

Step L-Conduct Effectiveness Evaluation

This step provides an assessment of the impacts of intersection projects that have been implemented, and identifies how they may be improved for future implementations. The purpose of the effectiveness evaluation of intersection projects is to determine the degree to which the intersection safety goals have been achieved. Without this evaluation step, it would be difficult to show that the projects are effective in helping to reach the strategic goals, and program continuation may be difficult to justify. Also, if the evaluation finds that intersection projects are not performing as well as expected, it is important to recognize this as early as possible so resources can be redirected toward other projects that could potentially be more effective. Alternatively, if the evaluation finds that intersection projects are resulting in greater crash reduction benefits than anticipated, consideration can be given to increasing their use. Such evaluations may serve as eligibility criteria for the use of certain funding.

Enforcement projects may be evaluated by measuring traffic speeds or instances of red-light-running.

Education programs may be evaluated by surveys of the target audience.

EMS programs may be evaluated by noncrash measures, such as dispatch times, response times, transport times, and medical outcomes

One of the most meaningful evaluations used to demonstrate effectiveness and to quantify achievement toward the strategic goals is a before-after study. A before-after study compares crash frequencies and rates before project implementation to those after project implementation. Ideally, three to five years of crash data from both the before period and the after period are used in the study. Comparing data from fewer years, especially in the after period, is often necessary. Shorter evaluation periods may be acceptable but may introduce the potential to capture anomalies in the data that provide less accurate results. Crashes are infrequent and randomly dispersed (both over time and throughout the roadway system); therefore, most projects can only be meaningfully evaluated for their effectiveness a few years after implementation. However, some projects may lend themselves to other forms of evaluation that can serve as interim measurements before complete crash data is available. These might include traffic conflict studies, public opinion surveys, behavioral studies (observed seatbelt use, for example), and speed studies. These surrogate measures are typically associated with potential crashes, so an evaluation of these trends may help an agency estimate expected trends in crash frequency as well as how well the project will help meet the strategic goals. Ultimately, evaluations based on crash data analyses are desirable.

The NCHRP Report 500, Volume 21, Guide for Addressing Safety Data and Analysis in Developing Emphasis Area Plans(24) provides guidance on sources of safety data. This guide presents effectiveness evaluation procedures that can be applicable to jurisdictions that have extensive safety data files (i.e., crash, roadway inventory, intersection inventory, traffic) as well as those with limited safety data (i.e., crash data only).

There are a variety of computer programs that may be helpful in efficiently evaluating safety projects and treatments. SafetyAnalyst(25) is a new software that provides a set of tools for analyzing a State's entire network of intersections, a subset of intersections, or a single intersection. The SafetyAnalyst countermeasure evaluation tool is capable of assessing the safety effectiveness of a single countermeasure at specific intersections or the collective effectiveness of a group of countermeasures in which the same countermeasures were implemented at specified intersections. Before-after evaluations can be conducted with SafetyAnalyst to determine whether a project has resulted in a percentage change in intersection crash frequencies or a shift in the proportion of specific intersection collision types.

Once the benefits of an intersection improvement are determined, the effectiveness of the project can be determined and compared to other improvements. The measure of effectiveness most often used in safety is determined by dividing the resulting benefit by the improvement cost (called the B-C ratio). The actual crash benefits, such as the number of lives or injuries saved, should be converted to a monetary estimate value that can be compared to the improvement costs. The B-C ratio for different improvements can then be compared to determine the more cost effective improvement types. Evaluators may assign an estimated localized benefits factor for crash impacts or may utilize factors used by others, such as insurance organizations or the public agencies. However, it is important to understand that safety treatments can still be desirable even if the B-C ratio is below a value of one, which would seem to indicate that the benefit derived may be of less worth than the improvement cost. This is because the assigned benefits value is only useful in comparing the effectiveness between improvements. It is not helpful for assessing an individual improvement's merit, because the assigned benefit value can not truly represent the total losses resulting from crashes.

The evaluation of intersection safety projects after their implementation helps to ensure that each project is as effective as possible at reducing the number of intersection fatalities and severe injuries. Evaluation results are useful in determining the content and focus of future projects that should optimize the cost effectiveness of intersection safety projects and help to achieve the strategic goals.

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