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                        Roadway Safety Information Analysis: A Manual for Local Rural Road Owners


            
            In This Section
        Local and Rural Road Safety Program
                Training, Tools, Guidance and Countermeasures for Locals Practitioners
                Crash Facts
                
                2. Safety Information Collection
Several types of data are needed to develop an effective safety program. This information can assist agencies in identifying locations with safety issues, prioritizing locations, and identifying the most appropriate treatments. It is difficult to solve a problem until information is collected and analyzed to determine the nature of the problem. There are three common types of data needs for a safety project or program:

Crash data;
	Roadway characteristic data; and
	Exposure data.

2.1. Crash Data

Crash history data is the primary source of information regarding the traffic safety environment, driver behavior, and vehicle performance. In order to address safety problems, traffic safety data should be timely, accurate, complete, consistent, integrated, and accessible. Good quality data have the potential to improve problem identification, prioritization of project selection, and evaluation of the effectiveness of countermeasures.4

Compared to Federal and State safety professionals, local practitioners tend to be more aware of locations with a history of crashes within their own jurisdictions due to the size of the area and news-worthiness of local traffic crashes. This knowledge, coupled with actual crash data, can aid the practitioner in identifying factors contributing to crashes and allow them to choose improvements to address these issues. The primary sources of crash data for local practitioners include:

Law enforcement crash reports;
	State crash database;
	Fatality Analysis Reporting System (FARS) database;
	Hospital data; and
	Public notification of safety concerns.

2.1.1. Law Enforcement Crash Reports

The primary and most comprehensive sources of information used to populate crash databases are the crash reports completed by State and local law enforcement organizations. Crash reports are the record of a traffic crash that has occurred on a public roadway. The format of the report varies by State, and sometimes by jurisdiction within a State. See Appendix A for an example of a State crash report.

Crash reports generally include the following information about the incident:

Date & time of crash;
	Crash severity;
	Crash type;
	Location & roadway information;
	Weather;
	Number and types of vehicles involved;
	Driver information (e.g., name, age, gender); and
	Contributing circumstances.By reviewing the information provided on crash reports over a period of time, recurring variables may be discovered to help pinpoint which factors are contributing to crashes.

The types of information collected and data collection methods used by law enforcement officers vary. Documentation methods among individual officers in the same jurisdiction also vary at times. The local practitioner should be aware of these variances during the review and analysis of crash reports.

There are a number of crash reporting issues that should be considered by law enforcement officers and safety practitioners when working with crash reports. These include:

**Location Coding**. Exact location of a crash is sometimes difficult to determine because the location of impact is often not where the vehicles come to rest. Referencing crash locations is often dependent on the level of technology used, the experience of the officers at the scene, and the approach used by the jurisdiction.

Typical methods include:

Distance from known reference point;
	Street address;
	Milepost; and
	Global Positioning System (GPS) – latitude and longitude coordinates.Limited resources often preclude the use of expensive technology, and reference points may be long distances apart, affecting accuracy. In a situation where GPS data is available, Geographic Information Systems (GIS) tools may be available to use these data for in-depth analysis and mapping.

Regardless of the method used, the location of each crash is an important data element for safety analysis.

**Crash Type Definitions**. Various jurisdictions may define crash report terms differently. For example, whereas rear-end and head-on crash types may be standard classifications in some areas, other regions may interpret these classifications differently or include additional classifications.

**Threshold for Reportable Crashes and Severity Determination**. States across the country use varying criteria to determine when a crash is deemed reportable and to define crash severity. Reportable crashes are crashes that include a fatality, injury, or property damage cost meeting a specified threshold. Most States have an estimated property damage cost threshold for a property damage only (PDO) crash to be considered reportable. In some States, if the vehicle can be driven away from the scene of the crash and no one is injured, it is not considered a reportable incident.

Jurisdictions are generally consistent with regard to the definition of a fatal crash; but as the severity of a crash diminishes, the classifications can vary by state. The severity of an injury crash is often difficult to determine at the scene and can be subjective based on the reporting officer if follow-up with hospital or Emergency Medical Services (EMS) is not conducted. Local practitioners should be aware of the issues in their States and local jurisdictions during crash data review and subsequent analysis.

Practitioners should also be aware that data issues such as missing, contradictory, and erroneous information have the potential to skew analysis and result in inefficient decision making. Coordination between law enforcement personnel and local road practitioners is important to ensure the efficient collection of crash data.



2.1.2. State Crash Database

Statewide crash databases typically offer comprehensive records on all reported crashes. They are compiled from State, county, and municipal law enforcement agencies submitting crash reports to a central State repository. State crash databases typically include the information collected at the scene of the incident.

However, State repositories can vary by agency, depending on the state. Data compilation and dissemination methods can also differ by State and not all States share their collected crash data with local jurisdictions. Moreover, local crash data in the repository can be incomplete. Local practitioners should be aware of the issues in their State and should identify the relevant points of contact necessary to obtain further information.

State data on crash types can provide clues regarding the potential for future severe crashes and countermeasures that could help. For example, if only non-injury roadway departure crashes have been recorded at a particular curve over a period of time, these incidents could be a precursor to a severe crash in the future if this location is not treated, since rural roadway departure crashes tend to be more severe than other types.



2.1.3. FARS Database

The Fatality Analysis Reporting System (FARS) is a national database of fatal crashes that occurred on the national public roadway network. It is maintained and operated by the National Highway Traffic Safety Administration (NHTSA).

FARS contains data derived from a census of all fatal traffic crashes within the 50 States, the District of Columbia, and Puerto Rico. FARS was developed to provide an overall measure of highway safety at the national level, to help identify traffic safety problems, to suggest solutions, and to help provide an objective basis upon which to evaluate the effectiveness of standards and highway safety programs among the States.5

Each State provides specific fatal crash information in a standard format to FARS. The data originate from State accident reports. Once collected by the FARS analysts, the data are recoded to match the standard FARS forms. FARS data are used to answer questions regarding the roadway, vehicle, and driver factors that contribute to traffic safety.6 The benefit to the FARS data is that it includes information on every fatal crash that has occurred within a State; so if a jurisdiction has no other reliable source of data, FARS can provide a starting point.

The FARS dataset is limited to those crashes involving a fatality. In a local rural setting, fatal crashes are relatively rare and random; therefore, FARS data may not provide the best indication of locations with identifiable safety issues.



2.1.4. Hospital Data

If on-scene crash data is unavailable, other potential sources of information are local Emergency Medical Services (EMS) and medical centers. EMS data can provide information regarding the locations and degree of EMS responses to traffic crashes. Similarly, hospitals may have some information available regarding emergency room visits or other admissions connected to traffic crashes. Due to a number of Federal and State regulations regarding the privacy of medical information, the availability of these data could be limited and will vary by State.

The Crash Outcome Data Evaluation System (CODES) links crash records to injury outcome records collected at the scene and en route by EMS; by hospital personnel after arrival at the emergency department or admission as an inpatient; or on the death certificate at the time of death. CODES is designed to foster and cultivate crash-outcome data linkages for highway safety applications by State and local practitioners.7

Analyses of linked data can help traffic safety professionals and coalitions to determine and implement data-driven traffic safety priorities. In many States, the State Department of Health (or similar agency) has access to the CODES linkage data, and this information in combination with the State crash database and FARS data, can be beneficial to local safety practitioners supporting safety initiatives.



2.1.5. Public Notification of Safety Concerns

Potential infrastructure issues, perceived safety concerns, or other traffic-related situations are sometimes reported to the local agency by citizens or citizen groups. The notification is typically delivered by telephone call or e-mail to the officials of a local jurisdiction, and a response is often requested.

The public official should compile records of these notifications so that multiple notifications of the same location can be identified. While this is primarily anecdotal information, public notifications can serve as indicators that a problem may exist and could warrant further review and analysis. Additionally, open communication with local citizens can help practitioners identify potential highway safety issues in the community.

Table 1 shows how a simple database could be designed to capture and store information from the various sources previously discussed.



**Table 1. Sample Local Jurisdiction Crash Database**
	Location
			Source of Information
			Date (MM/ DD/ YYYY)
			Type of Information
			Problem
			Crash?
			Nature of Crash
			Crash Type
			Time of Day (24 hr time)
			Weather Conditions
			Traffic Conditions
			Action?
			Date of ActionIntersection – Rt 123 and Fox Mill Road
			Local Newspaper
			3/8/2008
			Citizen Complaint
			Speeding
			N
			NA
			NA
			
			
			
			PendingRoute 123 West / 1/2 mile south of intersection with Fox Mill Road to intersection
			Local Newspaper
			12/1/2007
			Citizen Complaint
			Drivers losing control at curve
			N
			NA
			NA
			
			
			
			PendingIntersection – Route 657 and Glade Drive
			Local Police
			2/1/2008
			Police Report
			Crash Report
			Y
			Vehicle traveling North on Route 657 hit while making left turn onto Glade Drive
			Right angle
			7:22
			Clear
			Light volumeRoute 657; 1/2 mile south of Glade Drive
			Local Police
			4/1/2008
			Police Report
			
			Y
			Driver hit tree on shoulder; single vehicle
			Roadway departure; hit stationary object
			23:03
			Snow
			Light volumeIntersection – Route 657 and Clifton Road
			State Police
			10/4/2008
			Police Report
			Crash Report
			Y
			Vehicle traveling West on Clifton road rear-ended at intersection
			Rear-end
			19:21
			Rain
			Light volumeClifton Road; South of Veirs Mill Road
			State Police
			11/11/2008
			Police Report
			
			Y
			Driver ran off road on curve; exceeding posted speed
			Roadway departure; on curve
			12:23
			Rain
			Light volumeIntersection – Route 657 and Glade Drive
			Local Police
			11/12/2009
			Police Report
			Crash Report
			Y
			Vehicle traveling West on Glade collided with vehicle on Route 657
			Right angle
			10:06
			Rain
			No trafficRoute 657; 1/4 mile South of Glade Drive
			Local Police
			11/24/2009
			Police Report
			
			Y
			Driver ran off road; single vehicle
			Roadway departure
			23:04
			Rain
			No trafficIntersection – Middlebrook Pike and Waples Mill Road
			Maintenance Crew
			12/1/2009
			Observation
			Missing Stop Sign
			N
			NA
			NA
			
			
			
			Replaced Stop Sign
			12/19/2009Middlebrook Pike; 1 mile North of Running Cedar Road
			Maintenance Crew
			12/12/2009
			Observation
			Sign Knocked Down
			N
			NA
			NA
			
			
			
			Advanced Curve Warning Sign Replaced
			1/8/2010

2.2. Roadway Data

It is also valuable to obtain information about the roadway infrastructure. The following roadway data are often used to assist practitioners in safety analyses:

Roadway surface (dirt, aggregate, asphalt, concrete);
	Lane (number, width);
	Shoulder (type, width);
	Median (type, width);
	Roadway alignment (curve, straight);
	Intersection (number of legs, configuration); and
	Traffic control devices present (signs, pavement marking, traffic signals).This information can be combined with crash data to help local practitioners identify appropriate locations and treatments to improve safety. For example, if a segment of roadway is experiencing a high number of roadway departure crashes, analysis of the inventory of roadway elements could reveal that the roadway does not have edgeline pavement markings. An appropriate countermeasure could be to install edgeline pavement markings to provide guidance to motorists to stay on the traveled way.



2.3. Exposure Data

The raw number of crashes can sometimes provide misleading information about the most appropriate locations for treatment. Introducing exposure data helps to create a more effective comparison of locations. Exposure data provide a common metric to the crash data so roadway segments and intersections can be compared more appropriately.

The two most common types of exposure data used are traffic volume and roadway miles.

**Traffic volume**. A count of the number of vehicles along a segment of road or entering an intersection can provide information to the practitioner for comparison. For example, if two intersections have the same number of crashes but different entering traffic volumes, the location with fewer vehicles (i.e., less exposure) will have a higher *crash rate*, meaning that vehicles were more likely to have experienced a crash at that location. This rate reflects the fact that an increase in the number of vehicles has an effect on the expected number of crashes.
	**Roadway miles**. In many cases, traffic count data is not available and the cost to collect the information may be prohibitive for local jurisdictions. An alternative method for analyzing the data is to use the route's length in miles. If two roadways have a similar number of crashes but differing lengths, calculations will indicate the shorter road has experienced more crashes per mile.



4 Federal Highway Administration, *Crash Data Improvement Program Guide*, April 2010. Available at: https://www.govinfo.gov/content/pkg/GOVPUB-TD2-PURL-gpo3577/pdf/GOVPUB-TD2-PURL-gpo3577.pdf [ Return to note 4 ]



5 U.S. Department of Transportation, National Highway Transportation Safety Administration, "Fatality Analysis Reporting System Fatal Crash Data Overview" brochure, DOT HS 809726, April 2005. [ Return to note 5 ]



6 U.S. Department of Transportation, National Highway Transportation Safety Administration, "Fatality Analysis Reporting System (FARS) Encyclopedia" web site, http://www-fars.nhtsa.dot.gov [ Return to note 6 ]



7 CODES data is collected in a limited number of states. Local practitioners should consult their State highway agency or Local Technical Assistance Program (LTAP) center for additional information.[ Return to note 7 ]
      
  Book traversal links for 2. Safety Information Collection
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                    4. Countermeasure Selection ›
                
                Book:Roadway Safety Information Analysis: A Manual for Local Rural Road Owners
              1. Introduction
                2. Safety Information Collection
                4. Countermeasure Selection
                5. Case Studies
                6. Summary
                Appendix A. State Crash Report Example
                Appendix B. Resources U.S. DEPARTMENT OF TRANSPORTATION

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