Evaluation of Protected Left-Turn Phasing and Leading Pedestrian Intervals Effects on Pedestrian Safety

Pedestrian safety is an important public health issue for the United States, with pedestrian fatalities representing approximately 16% of all traffic-related fatalities in 2016. Nationwide, transportation agencies are increasing their efforts to implement engineering-based improvements that increase pedestrian safety. These agencies need statistically rigorous crash modification factors (CMFs) to demonstrate the safety effectiveness of such countermeasures, and to apply in benefit–cost analyses to justify their implementation. This study focused on developing CMFs for two countermeasures that show promise for improving pedestrian safety: protected or protected/permissive left-turn phasing, and leading pedestrian intervals (LPIs). Data were acquired from four North American cities that had installed one or both of the countermeasures of interest: Chicago, IL; New York City, NY; Charlotte, NC; and Toronto, ON. The empirical Bayes before–after study design was applied to estimate the change in expected crash frequency for crashes following treatment. The protected left-turn phasing evaluation showed a benefit in reducing vehicle–vehicle injury crashes, but did not produce statistically significant results for vehicle–pedestrian crashes. For those crashes a disaggregate analysis did reveal that this treatment could be especially beneficial where pedestrian volumes exceed 5,500 per day. The LPI evaluation showed a statistically significant reduction in vehicle–pedestrian crashes with an estimated CMF of 0.87.

Safety Impacts of Transit Signal Priority Using a Full Bayesian Approach

Transit signal priority (TSP) is a strategy that prioritizes the movement of transit vehicles through a signalized intersection to provide better transit travel time reliability and minimize transit delay. Although TSP is primarily intended to improve the operational performance of transit vehicles, it may also have substantial safety benefits. This study explored the potential safety benefits of the TSP strategy deployed at various locations in Florida. An observational before–after full Bayes (FB) approach with a comparison group was adopted to estimate the crash modification factors (CMFs) for total crashes, rear-end crashes, sideswipe crashes, and angle crashes. The analysis was based on 12 corridors equipped with the TSP system and their corresponding 29 comparison corridors without the TSP system. The deployment of TSP was found to reduce total crashes by 7.2% (CMF = 0.928), rear-end crashes by 5.2% (CMF = 0.948), and angle crashes by 21.9% (CMF = 0.781), and these results are statistically significant at a 95% Bayesian credible interval (BCI) except for the rear-end crashes. On the other hand, sideswipe crashes increased by 6% (CMF = 1.060) although the increase was not significant at a 95% BCI. Overall, the results indicated that TSP improves safety. The findings of this study may present key considerations for transportation agencies and practitioners when planning future TSP deployments.

Investigating Approaches to Advancing Knowledge on the Effects of Road Safety Treatments: An Application to Ontario Rural Two-Lane Highways

Crash modification factors (CMFs) are important tools for understanding the safety benefits of treatment options. However, CMFs typically lack variability as they apply a single factor to all the sites that are treated by these road safety measures. Crash modification functions (CMFunctions) are one way to capture the variability of CMFs as a function of independent variables. This research conducted a case study on the application of edgeline, centreline and dual rumble strip treatments on Ontario provincial highways and investigated CMF variability by developing CMFunctions as well as separate CMFs for tangent and curved sections. Curved sections experienced greater benefits from the application of the rumble strips. In conducting the study, the Highway Safety Manual’s application of rumble strip CMFs to Ontario roadways was also explored.

Case studies on estimating crash modification factors for treatment combinations with empirical investigation of dual rumble strip application in Ontario

Crash modification factors (CMFs) are used to quantify the impact of safety treatments. These treatments are often used in combination and so the need for estimating CMFs for simultaneous applications arises. Applications of new heuristic methods in combining treatments showed mixed results, indicating a need for sound judgement in their usage. A case study for centreline and edgeline rumble strips on Ontario highways resulted in combined CMFs of 0.805, 0.79, 0.743, 0.799, and 0.689 for total, injury, PDO, single vehicle, and approach & sideswipe crash types, respectively. The estimates were comparable to the CMFs estimated in other research for actual dual rumble strip application. CMFs developed separately for tangent and curved segments showed that both rumble strip types are more effective on curved segments.

Exploring the transferability of crash modification factors: case studies on passing lanes and dual rumble strips on Ontario two-lane highways

The safety effects of design and other highway improvement options are specified through Crash Modification Factors (CMFs). CMFs for two low cost safety treatment measures -- passing lanes and dual application of center line and shoulder rumble strips -- are explored separately in this paper. Using data provided from previous studies conducted in the United States, and generalized linear modeling, the transferability of the US-based knowledge on safety effects of passing lanes and rumble strips for application in Ontario was explored. It was found that the safety effects were consistent for passing lanes in Michigan and Ontario and a Crash Modification Function was developed relating the CMF to length of passing lane for the combined data. The dual rumble strip effects were also reasonably consistent with results from a limited analysis of Ontario data and are recommended for application in the province.

Investigating Approaches to Advancing Knowledge on the Effects of Road Safety Treatments: An Application to Ontario Rural Two-Lane Highways

Crash modification factors (CMFs) are important tools for understanding the safety benefits of treatment options. However, CMFs typically lack variability as they apply a single factor to all the sites that are treated by these road safety measures. Crash modification functions (CMFunctions) are one way to capture the variability of CMFs as a function of independent variables. This research conducted a case study on the application of edgeline, centreline and dual rumble strip treatments on Ontario provincial highways and investigated CMF variability by developing CMFunctions as well as separate CMFs for tangent and curved sections. Curved sections experienced greater benefits from the application of the rumble strips. In conducting the study, the Highway Safety Manual’s application of rumble strip CMFs to Ontario roadways was also explored.

Exploring the transferability of crash modification factors: case studies on passing lanes and dual rumble strips on Ontario two-lane highways

The safety effects of design and other highway improvement options are specified through Crash Modification Factors (CMFs). CMFs for two low cost safety treatment measures -- passing lanes and dual application of center line and shoulder rumble strips -- are explored separately in this paper. Using data provided from previous studies conducted in the United States, and generalized linear modeling, the transferability of the US-based knowledge on safety effects of passing lanes and rumble strips for application in Ontario was explored. It was found that the safety effects were consistent for passing lanes in Michigan and Ontario and a Crash Modification Function was developed relating the CMF to length of passing lane for the combined data. The dual rumble strip effects were also reasonably consistent with results from a limited analysis of Ontario data and are recommended for application in the province.

Case studies on estimating crash modification factors for treatment combinations with empirical investigation of dual rumble strip application in Ontario

Crash modification factors (CMFs) are used to quantify the impact of safety treatments. These treatments are often used in combination and so the need for estimating CMFs for simultaneous applications arises. Applications of new heuristic methods in combining treatments showed mixed results, indicating a need for sound judgement in their usage. A case study for centreline and edgeline rumble strips on Ontario highways resulted in combined CMFs of 0.805, 0.79, 0.743, 0.799, and 0.689 for total, injury, PDO, single vehicle, and approach & sideswipe crash types, respectively. The estimates were comparable to the CMFs estimated in other research for actual dual rumble strip application. CMFs developed separately for tangent and curved segments showed that both rumble strip types are more effective on curved segments.