Transportation Research Record: Journal of the Transportation Research Board

A guiding principle of modern traffic safety professionals attempting to reduce the risks associated with traffic is to holistically address traffic safety as a multidisciplinary partnership issue. The systems approach focuses on the relationships and dependencies between the various elements of the traffic system. The C3-R3 Systems Approach to traffic safety is introduced; the building blocks of the C3-R3 approach are three entities (the road user, the vehicle, and the road environment), three pre-crash timeline phases (creation, cultivation, and conduct), and three postcrash timeline phases (response, recovery, and reflection). This approach is proposed as a framework for multidisciplinary traffic safety professionals to research traffic safety issues in an integrated, systematic manner. The C3-R3 approach provides an enhanced systematic framework that more clearly identifies the stages at which traffic safety professionals can intervene to promote road safety. The graphical representation of the C3-R3 system, as presented, emphasizes the convergence of the entities as the timeline proceeds toward a crash event and their subsequent redivergence in the postcrash timeline. Every combination of entity and timeline phase represents a cell in the C3-R3 system; the contents of each cell represent the individual elements that traffic safety professionals need to focus on and understand in order to reduce the crash risk. The C3-R3 Systems Approach represents a starting point to encapsulate the systems approach concepts in traffic safety. It is expected that as more professionals adopt systems thinking, the C3-R3 approach will continue to evolve, expand, and improve.

The lap and shoulder belt combination can reduce the risk of fatal motor vehicle crash injuries to front-seat occupants by 45% and the risk of moderate-to-critical injuries by 50%. The significant life- and cost-saving potentials of these restraining devices, installed in virtually every vehicle in the United States, are well recognized, but the benefits come only from their actual use. Identified are two demographic characteristics of unrestrained persons involved in fatal crashes, age and sex, to provide a basis for targeting educational and promotional efforts to encourage restraint use among the most vulnerable groups. Analyses are based on 1996 to 2000 crash data from the Fatality Analysis Reporting System, compared with exposure data from the 1995 Nationwide Personal Transportation Survey. This study found that the risk of sustaining fatal injuries in a vehicle crash is reduced by 54% when occupant restraints are used. A much higher proportion of young males in the 16 to 19 and 20 to 24 age groups involved in fatal crashes do not use restraints, about 1.72 and 1.69 times greater, respectively, than those who do use restraints. While females in these age groups are also overrepre-sented, the extent of this excess is less than that of males. This underscores the need to find ways to educate young people, especially young males, about the benefits of restraint use.

In compliance with its mandatory seat belt law, Hawaii is a high-use state. Seat belt use from 1998 to 2001 has averaged 81%, compared with 70% nationally. Efforts to increase belt use beyond 90% have not been successful, at least until the most recent effort, which entailed a combined enforcement and public information campaign. Described are patterns of belt use over time and the effects of the "Click It or Ticket" campaign that was launched this year. In January 2002, before the program was started, there was an overall belt use rate of 83.5%. After increased enforcement and publicity, Hawaii experienced an immediate increase in belt use by 6.9%. Belt use increased dramatically in each of the state’s four counties: in Honolulu, a 7.5% increase; Maui, 10.1% increase; and Kauai, 5% increase. The county of Hawaii, however, increased its rate by only 2.7%. Additional surveys in the months following the campaign indicated that in the days and weeks immediately after the Click It or Ticket campaign, there was a significant drop-off in belt use; but 144 days after, belt use in Honolulu County has stabilized at above 90%. This is surprising because the actual observed current rate is higher than the rate projected on the basis of observations conducted during the weeks immediately after the campaign was initiated. While more surveys and analysis are planned, the campaign was successful in Hawaii. Comments are provided about increasing belt use in a high-use state and implications are described for other traffic safety programs and initiatives.

Speed limit enforcement cameras (SLECs) have been in operation in Great Britain since 1991. However, there is still considerable dispute regarding their effectiveness in reducing accident rates. The aim of this research was to analyze the effects of SLECs on accident rates in Cambridgeshire, United Kingdom, using time series data collected over an 11-year period. A time series analysis of the accident data revealed the presence of both trend and seasonality components. A method was developed to remove the influence of these two components from the data and compare mean accident levels before and after installation of the camera. The method was also constructed in such a way that it would be able to distinguish between the actual effects of the camera installation and the effects of regression to the mean. The initial investigation into the effects of SLECs showed an average decrease over sites in the monthly accident frequency by around 18%; a more detailed analysis suggested that the best approximation of the effect of the introduction of a SLEC is a decrease in injury accidents by 31.26%, thus giving clear evidence that SLECs do indeed contribute to a significant decrease in accident numbers.

Washington, D.C., implemented a speed camera enforcement program in 2001. Vehicle speeds were measured before and after the program. Seven sites in Washington were selected randomly from a total of 60 targeted enforcement zones. Speed data were collected 1 year before enforcement and approximately 6 months after enforcement began. Results indicated that mean traffic speeds and the proportion of drivers traveling more than 10 mph above the speed limit—fast enough to warrant a speeding ticket—were reduced at each of the Washington study sites. At eight comparison sites in nearby Baltimore, Maryland, where speed camera enforcement was not in place, no decline in traffic speeds was observed. Overall, mean speeds at Washington sites declined by a statistically significant 14% compared with Baltimore sites, and the proportion of vehicles exceeding the speed limit by more than 10 mph declined 82%. These findings indicate that speed camera enforcement reduced speeding on surface streets throughout Washington. On the basis of prior research, such speed reductions can be expected to reduce the frequency and severity of motor vehicle crashes.

Statistics consistently indicate that red-light running has become a significant safety problem throughout the United States. Comprehensive guidelines for treating red-light running at problem intersections have been developed. Unfortunately, these guidelines do not include a tool or technique for quantitatively determining if a problem exists and if a countermeasure is truly effective. The objective of this work is to describe the development and calibration of such a tool. The calibrated prediction model developed for this research indicates that red-light running increases with flow rate, speed, and dense platoons arriving at the end of the phase. It was also found that red-light running decreases with increasing cycle length and cross-street width, and when back plates are used on the signal heads. Uses for the calibrated model are described.

Red-light running is one of the leading causes of crashes in urban areas in the United States. A number of strategies are available to address this problem, including engineering countermeasures, educational campaigns, and improved law enforcement. Law enforcement agencies are increasingly relying on automated systems using photographic devices to enforce red-light-running laws. While automated enforcement systems appear to have wide public support, there is considerable confusion among drivers, engineers, planners, and decision makers as to the legality and constitutionality of those systems. The debate is particularly acute when it comes to issues such as privacy, use of information, and constitutional rights. These issues are analyzed and legal strategies are compared in states that have passed or attempted to pass legislation to regulate automated enforcement. The analysis highlights differences among states depending on their statutory laws and whether red-light violations are treated as civil or criminal offenses. The analysis reveals major differences in the way states legislate program details, which, in turn, affect program implementation. Also included is a review of current European red-light-running legislation, where automated enforcement systems have a longer history than in the United States.

To compare the safety effects of a uniform speed limit (USL) for all vehicles and a differential speed limit (DSL) for cars and heavy trucks, crash, speed, and volume data for rural Interstate highways for the period 1991 through 2000 were obtained from nine states. These states were divided into four policy groups based on the type of speed limit employed during the period: maintenance of a uniform limit only, maintenance of a differential limit only, a change from a uniform to a differential limit, and a change from a differential to a uniform limit. Statistical tests (analysis of variance, Tukey’s test, and Dunnett’s test) and the empirical Bayes method were used to study speed and crash rate changes in the four policy groups. The focus here is only on the statistical tests. The safety effects of DSL and USL were not different within the scope of the study. The mean speed, 85th percentile speed, median speed, and crash rates tended to increase over the 10-year period regardless of which type of speed limit was employed. When all sites within a state were analyzed, temporal differences in these variables were often not significant.

Crashes involving large trucks and passenger cars are important topics for research and countermeasure development since they represent more than 60% of all fatal truck crashes and because the passenger car occupant is much more likely to be killed. This study (a) examined “fault” in total car–truck crashes using North Carolina Highway Safety Information System (HSIS) data for comparison with fault analyzed in previous studies of fatal crashes, (b) used general estimates system (GES) crash data to verify unsafe driving acts (UDAs) identified by expert panels in past studies, and (c) used North Carolina HSIS data to identify critical combinations of roadway facility type, roadway location, and crash type based on “total harm”—a measure combining both the frequency and severity of the crash. Fault in total North Carolina car–truck crashes was found to differ significantly from past fatal crash studies, with the truck driver being at fault more often than the car driver both overall and in certain crash types. Car drivers continue to be at fault much more often in head-on and angle crashes. While it was not possible to analyze all UDAs identified in prior studies, when possible, the current analyses revealed differences between the GES crash data results and the expert-based results, pointing to the need for better UDA methods if they are to be used to target treatments. Finally, using the total-harm analysis with North Carolina car–truck crashes indicated that undivided rural arterials and collectors should be primary targets for further investigation and for treatment.

Described is one specific effort to better estimate commercial motor vehicle-related exposure at the state level in order to better determine commercial motor vehicle-related crash rates for state and federal programs. Limitations in the crash and exposure data affect the Federal Motor Carrier Safety Administration and a state’s ability to plan and assess operations and conduct ongoing analyses of program effectiveness. One important limitation has been the lack of reliable estimates of commercial motor vehicle exposure data at the state level. Exposure data, for the purpose of this report, are defined as the number of truck and bus vehicle miles traveled (VMT). Described is the methodology that was developed to calculate adjusted state VMT for commercial vehicles; results are presented for 1999 and 2000. The results support estimation of crash involvement rates for each state and provide exposure data for other analytical studies. The methodology to calculate adjusted state VMT for commercial motor vehicles has resulted in improved information resources in support of all crash analyses. The adjusted state VMT for commercial vehicles supports measurement of program effectiveness and development of countermeasures to promote motor carrier safety. The adjusted state VMT for commercial motor vehicles methodology and the commercial vehicle fatal-crash involvement rate reports enable state and federal agencies to better focus their safety programs and enforcement resources.