Multijurisdictional Safety Evaluation of Red Light Cameras

Abstract

The use of red light camera (RLC) systems has risen dramatically in the United States in recent years. The size of the problem, the promise shown by RLC systems in other countries, and the paucity of definitive U.S. studies have motivated a multijurisdictional U.S. study. The fundamental objective of this study, which was sponsored by FHWA, was to determine the effectiveness of the RLC systems in reducing crashes at monitored intersections as well as jurisdictionwide. Phase I involved the development of a detailed experimental design that included collection of background information, establishment of study goals, selection of potential study jurisdictions, and specification of statistical methodology. In Phase 2, an empirical Bayes before-and-after study used data from seven jurisdictions across the United States, with a total of 132 treatment sites. Effects detected were consistent in direction with those found in many previous studies—a decrease in right-angle crashes and an increase in rear-end crashes—although both effects are somewhat lower than those reported in many sources. The extent to which the increase in rear-end crashes negates the benefits for right-angle crashes is unclear and points to the need for an examination of the economic cost of crashes, which is the subject of a companion paper, to aggregate the effects on rear-end, right-angle, and other crash costs. That second paper seeks to isolate all factors that would favor the installation of RLC systems by using the aggregate economic benefit as the outcome variable. There were weak indications of a spillover effect, which point to a need for a more definitive, perhaps prospective, study of this issue.

The impact of red light cameras on safety in Arizona

“…A national study involving multijurisdictions used the year of the very first RLC installation at treated sites as the 'start date' for comparison sites. They concluded that there were weak indications of spillover effects that point to a need for a more definitive, perhaps prospective, study of this issue (Council et al, 2005a;Persaud et al, 2005). In this study, the effects on all 4 approaches and those on target approaches (i.e., the RLC equipped approach) are separately quantified and the spillover effects are calculated by subtracting the effects on the target approach from those on all approaches.…”

“…In contrast, the presence of RLCs increases the likelihood of rear-end crashes because some drivers will stop abruptly in order to avoid a potential ticket, causing the following vehicle to hit the lead vehicle. Thus, it is generally accepted that RLCs have the potential to reduce angle and left-turn crashes at signalized intersections and to increase rear-end crashes on the intersection approach on which the RLCs are installed (McGee and Eccles, 2003;Retting et al, 2003;Council et al, 2005a;Persaud et al, 2005). Therefore, crashes related to RLCs are divided into two-crash types: those attributed to RLR (i.e., angle and left-turn crashes) and those caused by actions related to avoiding RLR (i.e., rear-end crashes).…”

“…In the case of rearend crashes, only those that occurred within 30 m (100 ft) from the center of the intersection were considered as target crashes. While a national study (Council et al, 2005a;Persaud et al, 2005) used "46 m (150 ft)" for choosing the RLC related rear-end crashes, "30 m (100 ft)" was used in this analysis-resulting in a more conservative analysis (compared to using 150 ft). Moreover, it should be noted that the selection of a static distance is justified mainly due to the ease of coding data but not on theoretical grounds.…”

“…If cameras have an effect on driver behavior that extends beyond the RLC equipped intersections, then other intersections in the area will likely also experience a decrease in angle crashes (McGee and Eccles, 2003). Previous research suggests that there are potential spillover effects from the use of RLCs (Retting et al, 1999;McGee and Eccles, 2003;Council et al, 2005a;Persaud et al, 2005;Yaungyai and Hobeika, 2005). In order to investigate potential spillover effects, the before and after study explained in the previous section should be applied to non-camera intersections in each jurisdiction.…”

“…In most studies, even though the degree of impact has varied from site to site, the overall results of the evaluations suggest that RLCs have contributed to reducing the frequency of right-angle crashes and to increasing the frequency of rear-end crashes (Retting and Kyrychenko, 2002;McGee and Eccles, 2003). However, previous research conducted recently reports that the results of most studies are likely to be invalid as the result of methodological difficulties (Retting et al, 2003;Persaud et al, 2005).…”