Comparison of road safety evaluation methods based on traffic crash information and traffic conflicts

The frequency and intensity of the traffic crashes cause great concern for traffic engineers community and they are finding accurate and realistic methods of modeling traffic flow and preventing traffic crashes. Evaluations of traffic safety in transportation systems have meant to identify hazardous locations and causal factors or have evaluated new safety programs or policies implemented in transportation systems. This paper compares methods of conventional road safety evaluation and discusses advantages / disadvantages of each method. For some decades safety evaluation methods have relied on analysis of historical crash data. Since crashes are random and rare events and, in most cases, are independent events, it is difficult to find a sufficient number of crashes on a road section in a relatively short time period (e.g., a month or even a year). Thus, multi-year collection of crash data is used in safety analysis. Another safety evaluation method that has been practiced though in small scale is traffic conflict techniques (TCT). The advantage of using TCT in safety evaluations is the ability to test or study a safety strategy or improvement applied on the roadway facility in a relatively short period of time compared with traditional methods, which are dependent on crash data. However, use of TCT is not popular; perhaps because it needs extensive resources to collect, extract, and analyze conflict information. Moreover, like crash data analysis, use of TCT also makes concerned authorities reactive to the problem by responding to the crashes that have already occurred. Lastly, necessities of alternative proactive safety evaluation techniques that can improve the quality of traffic safety evaluation are discussed.