The Iowa Highway Research Board has identified the development of a simplified handbook of transportation studies as a high priority for the state of Iowa. The Center for Transportation Research and Education (CTRE) at Iowa State University was chosen to develop such a handbook. A well-executed, well-documented study is critical in the decision-making process for many transportation-related projects and in reporting to elected officials and members of the community. As more research is conducted in the area of transportation, study procedures in many cases have become more complex. It is often difficult for local jurisdictions with limited staff, training, experience, and time availability to perform these studies. The most commonly used publication for traffic studies is geared toward transportation professionals and professional engineers. That defining document, Manual of Transportation Studies (Institute of Transportation Engineers, 2000), is over 500 pages and includes several dozen types of transportation studies. Many of the transportation studies described in the manual are rarely (if ever) used by local jurisdictions. Further, those studies that are frequently used are at times very complex and possibly very costly to perform exactly as described. Local jurisdictions without the staff expertise to understand and apply the manual’s various studies have a need for a simplified handbook of procedures to perform common traffic studies themselves or properly define a scope of work to hire a consultant to perform the studies. This handbook describes simplified procedures that are easy to apply and are written for all potential users (civil engineers and traffic engineers, public works mangers, city managers and attorneys, and the general public). This handbook has two primary objectives: The first objective is to develop a handbook of traffic studies that is convenient for Iowa jurisdictions to use in assessing traffic issues. The second objective is to develop a series of boilerplate scopes of work that local jurisdictions can use to hire outside consulting firms to perform traffic studies. This is Part 5 of the Handbook of Simplified Practice for Traffic Studies, 'Crash analysis'. Crashes are rare events. A typical intersection experiences less than one crash per million vehicles that navigate the intersection. Crashes occur because of various factors including the driver, vehicle, roadway, and environment. The primary source of crash data is the local law enforcement agencies. Local law enforcement agencies are usually an excellent source for current conditions at a particular crash location. Crash data are used to help understand why crashes occur, to help identify high-crash locations, to aid in the choice of safety programs or countermeasures, and to assist evaluations of countermeasure effectiveness (Robertson 1994). The main purpose of crash analysis is to improve safety by identifying crash patterns, mitigating crash severity, and reducing the number of crashes by adopting suitable countermeasures. (Author/publisher)
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