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NCHRP Report 500 Volume 21: Safety Data and Analysis in Developing Emphasis Area Plans (2008)
National Cooperative Highway Research Program (NCHRP)

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Neuman, Timothy R, Delucia, Barbara Hilger, Graham, Jerry L, Peck, Raymond C, Potts, Ingrid B, Harwood, Douglas W, Hutton, Jessica M, Council, Forrest M, Torbic, Darren John, Transportation Research Board. "Closure Good Data Produce Better Results." NCHRP Report 500 Volume 21: Safety Data and Analysis in Developing Emphasis Area Plans. Washington, DC: The National Academies Press, 2008.

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Front Matter (R1-R11)
Summary (1-4)
Section I - Introduction (5-5)
Introduction to Proposed Procedures (6-7)
Crash Data and Related Files (8-10)
Roadway Inventory Data (11-11)
Driver History Files (12-12)
National Emergency Medical Services Information System (NEMSIS) (13-13)
Local Data Files (14-14)
Closure (15-15)
Stage 1 Define/Choose One or More Issues/Emphasis Areas (16-16)
Stage 3 Define Treatment Strategies and Target Populations (17-26)
Summary (27-27)
Possible Program Types Spot versus System Programs (28-28)
Procedure 1 Choosing Roadway-Based Treatments and Target Populations When Treatment Effectiveness Is Known, and Both Crash and Non-Crash Data Are Available (29-33)
Procedure 2A Choosing Roadway-Based Treatments and Target Populations When Treatment Effectiveness Is Known and Mileposted Crash Data Are Available, but Detailed Inventory Data Are Not Available (34-35)
Procedure 2B Choosing Roadway-Based Treatments and Target Populations When Treatment Effectiveness Is Known and Neither Mileposted Crash Data nor Detailed Inventory Data Are Available (36-37)
Procedure 3 Choosing Roadway Treatments and Target Locations When Treatment Effectiveness in Terms of Crash/Injury Reduction Is Not Known (38-39)
Procedure 4 Choosing Treatments and Target Populations in Emphasis Areas for which Some Candidate Treatments Have Known Effectiveness Estimates and Other Treatments Do Not (40-41)
Possible Program Types Spot versus System Programs (42-42)
Procedure 1 Choosing Intersection Treatments and Target Populations When Treatment Effectiveness Is Known, and Both Crash and Non-Crash Data Are Available (43-46)
Procedure 2A Choosing Intersection Treatments and Target Populations When Treatment Effectiveness Is Known and Mileposted Crash Data Are Available, but Detailed Inventory Data Are Not Available (47-48)
Procedure 2B Choosing Intersection Treatments and Target Populations When Treatment Effectiveness Is Known and Neither Mileposted Crash Data nor Detailed Inventory Data Are Available (49-49)
Procedure 3 Choosing Intersection Treatments and Target Locations When Treatment Effectiveness in Terms of Crash/Injury Reduction Is Not Known (50-52)
Procedure 4 Choosing Treatments and Target Populations in Emphasis Areas for which Some Candidate Treatments Have Known Effectiveness Estimates and Other Treatments Do Not (53-53)
Procedure 3 Choosing Roadway User Treatments and Target Subgroups When Treatment Effectiveness in Terms of Crash/Injury Reduction Is Not Known (54-57)
Closure Good Data Produce Better Results (58-58)
General Strategic Considerations (59-59)
Procedure 3 Choosing Treatments and Target Subgroups Related To Illegal Driving Actions When Treatment Effectiveness in Terms of Crash/Injury Reduction Is Unknown (60-63)
Alternative Economic Analysis Procedure Choosing Treatments and Target Subgroups for Alcohol-Related Crash Strategies When Treatment Effectiveness in Terms of Alcohol-Related Crash/Injury Reduction Can Be Estimated (64-65)
Alternative Procedure Choosing Treatments and Target Subgroups for Alcohol-Related Crash Strategies Based On Existing DWI Program Needs (66-66)
Closure (67-67)
General Strategic Considerations (68-68)
Procedure 3 Choosing Treatments and Target Subgroups Related To Unsafe Driving Actions When Treatment Effectiveness in Terms of Crash/Injury Reduction Is Unknown (69-72)
Closure (73-73)
Procedure 3 Choosing Treatments and Target Subgroups for Crashes Involving Special Vehicle Types When Treatment Effectiveness in Terms of Crash/Injury Reduction Is Not Known (74-77)
Closure Good Data Produce Better Results (78-78)
Section X - Reducing Crashes in Work Zones (79-79)
Level 1 Analysis (80-81)
Level 2 Analysis (82-83)
Level 4 Analysis (84-85)
Procedure (86-88)
Closure (89-89)
Organizational Issues (90-90)
Data Improvement Strategies (91-92)
Closure Good Data Produce Better Results (93-93)
Key References (94-95)
Abbreviations used without definitions in TRB publications (96-96)

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93 using the analytic tools as well as conducting analyses on strategic-planning effort. The TRCC should have the lead in request. A data warehouse is also an ideal place for creation such an effort and the custodial agencies should be strong and management of merged datasets resulting from the participants and backers of the initiatives. While it is true that linkage between various traffic records components. federal grant dollars can be used in the initial stages of these Where necessary, the warehouse staff can help to control efforts, experience has shown that a dependency on grant access to restricted information while still ensuring that the funding does not bode well for the long-term viability of a data are available to legitimate users. system. Budgeting for the life-cycle costs of a system and find- · Promote the use of GIS and other advanced technologies that add ing ways to ensure that the system is self-sufficient (for both value to the information. The mapping capabilities of GIS are funding and other resources) are the keys to sustainability for an example of value added data management and analysis. the foreseeable future. The TRCC is an ideal group for mak- Mapping implies the ability to locate events (e.g., crashes, ing recommendations about the long-term health of the sys- citations, EMS runs, etc.) in a way that is also compatible with tem, but ultimately the funding to support this coordinated other location-based datasets (such as state and local roadway long-term effort must come from the state (and perhaps inventory files, traffic data, population and demographics). local) agencies with custodial responsibility over a portion of By layering the maps of safety-related events with roadway, the traffic records system. These agencies are not likely to traffic and other data, a rich picture of the safety problems for spend their money on other agencies' systems unless there is a state or local area can emerge. This information, when some obvious benefit to them in completing their own pri- shared with decision makers in the agencies responsible for mary mission. In addition, the decision to share information data collection, can provide them with a powerful resource technology resources may have to be taken at a higher level that helps them do their job. These decision makers, in turn, than even the custodial agencies' leadership. A consortium of are more likely to appreciate the value of collecting and re- data owners, collectors, and users is the best way to make the porting high-quality data in a timely fashion. This is but one case for the eventual pooling of resources. The TRCC and example of how an inter-agency partnership and returning Executive TRCC are viewed as a good starting point for data-for-data can help to improve cooperation and help to developing the argument in favor of shared resources. make the case for improved data quality. Ensuring that the local agencies have access to data and analytic resources (as in Closure ­ Good Data Produce Better Results the case of a data warehouse) is another way to give them an incentive to improve data quality. The use of highway safety data is integral to safety deci- · Establish web-based data entry/editing and analysis facilities for sions. The better and more complete the data, the better the use by agencies that cannot afford field data collection systems. resulting decisions. This guide has provided analytical meth- Data collectors (especially in law enforcement, the courts, ods that can assist the safety analyst in choosing and targeting and EMS) include some very small and not-well-funded safety improvement strategies in the 22 different emphasis organizations. Many of these smaller agencies do not areas of the AASHTO Strategic Highway Safety Plan. Alter- contribute a large amount of data individually, but taken as native methods have been presented for different levels of a group may be responsible for a meaningful portion of the available safety data ­ from crash data only to mileposted and overall highway and traffic safety information available in a linked crash, inventory, and traffic data. However, the con- state. Under current conditions, it is rare for these agencies sistent message presented throughout the guide is that the to be able to justify or afford field-data collection or other ad- "full" safety data systems will allow for more detailed analy- vanced systems. Even if the software is provided free of sis and more precise answers. Such systems do not currently charge, the cost of the equipment and training required to exist in all state and local jurisdictions that are tasked with the make use of the software may be prohibitive. In states facing responsibility for these safety decisions. This final section has this situation, one solution is to provide web-based access for provided a discussion of ways to improve existing data sys- data entry, data editing, and analysis to support these users. tems, including recommendations concerning how to better While the initial intent may be to support the small depart- coordinate the various organizations involved in collecting ments/agencies, the availability of a web-based system may and using the various forms of safety data and what specific appeal to medium and even large agencies as an alternative data-improvement strategies have proven to be successful in to implementing a system locally. the past. It is hoped that these recommendations will result in improvements in data that will lead to decisions that will help The selection of strategies for improving traffic records in solve one of the largest public health problems faced by the a state is best accomplished in the context of an overall United States ­ highway crashes.