Libby Thomas

Safety Effects of Automated Speed Enforcement Programs: Critical Review of International Literature

Automated speed enforcement programs were evaluated worldwide to ascertain the effectiveness of such programs at achieving safety benefits. Unlike previous reviews on this topic, a critical review process was used to determine the most likely range of probable safety effects of fixed and mobile automated speed enforcement programs. Among the 90 studies from 16 countries that were initially identified as potential safety evaluation studies, 13 met the criteria for detailed methodological review. On the basis of evidence from the best-controlled evaluation studies, injury crash reductions in the range of 20% to 25% appear to be a reasonable estimate of site-specific safety benefit from conspicuous, fixed-camera, automated speed enforcement programs. No conclusions were reached regarding site-specific effects of mobile enforcement programs. Estimates of systemwide crash reductions likely attributable to covert, mobile speed enforcement programs were based on different subsets of crashes (daytime casualty crashes and daytime speed-related crashes) and were limited to two studies, but also were in the range of 20% to 25%.

Evaluation of Miami-Dade Pedestrian Safety Demonstration Project

This studys purpose was to implement a comprehensive program to reduce pedestrian deaths and injuries among pedestrians in a large urban environment. Miami–Dade County, Florida, was selected as the studys focus. High-crash locations were targeted for countermeasure implementation and analysis. With pedestrian crash data (1996–2001), four zones within the county were identified as having abnormally high pedestrian crash experience. On the basis of crash characteristics and pedestrian factors (age, ethnicity), 16 education, enforcement, and engineering treatments were implemented to reduce pedestrian crashes in the four zones and countywide. A before-and-after study was used with three control groups to evaluate the effects of the pedestrian safety program on pedestrian crashes. A 3-year “after” period was used (2002–2004). Multivariate intervention autoregressive integrated moving average time-series analysis was used, along with nonparametric U-tests to test for statistically significant differences in pedestrian crash experience. Results showed that at the peak of the program effects in 2003 and 2004, the pedestrian safety program reduced countywide pedestrian crash rates by anywhere from 8.5% to 13.3%, depending on which control group was used. These effects translate to approximately 180 fewer crashes annually in the county, or 360 pedestrian crashes reduced for 2003 and 2004 combined, based on the more conservative 8.5% crash reduction. Countywide, the greatest crash reductions were found among children and adults as a result of the program. Educational and other measures to reduce crashes involving older pedestrians showed no effect. A number of lessons learned were identified for future program implementation.

Evaluation of Shared Lane Markings in Cambridge, Massachusetts

Shared lane markings (sharrows) convey the message that motorists and cyclists must share the travel way on which they are operating. The purpose of the markings is to create improved conditions for bicycling by clarifying where cyclists are expected to ride and reminding motorists to expect cyclists on the road. A before–after evaluation was conducted to compare how cyclists and motorists operated on a street with parallel parking in Cambridge, Massachusetts, with no markings versus with sharrows placed 10 ft (3.05 m) from the curb. This evaluation, which was part of a broader FHWA study on sharrows, was intended to help determine whether an alternative to the 11-ft (3.4-m) spacing recommended in the 2009 version of the Manual on Uniform Traffic Control Devices would be effective. Operational and safety measures for bicyclists and motorists were examined. Overall, safety effects appeared to be associated with the installation of the sharrows placed 10 ft (3.05 m) from the curb. Perhaps the most important effect was the 14-in. (36-cm) increase in spacing between motor vehicles in the travel lane and parked motor vehicles when no bicycles were present. This effect increased the operating space for bicyclists. Many variables related to the interaction of bicycles and motor vehicles also showed positive operational and safety effects.

Changing the Future? Development and Application of Pedestrian Safety Performance Functions to Prioritize Locations in Seattle, Washington

This study aimed to use robust analysis methods to identify and screen locations at risk for pedestrian crashes and injuries to help Seattle, Washington, a Vision Zero city, broaden treatment priorities beyond only high-crash locations. For this objective, data from the entire network were used to develop safety performance functions (SPFs) for two pedestrian crash types: total pedestrian crashes at intersections (a high frequency type) and a subset of intersection crashes involving through motorists striking crossing pedestrians (a high severity type). Many variables from roadway, built environment, census, and activity measures were tested. A similar but not identical set of variables, including measures of activity and intersection size and complexity, significantly contributed to crash prediction in both models. Pedestrian volume exhibited a curved relationship to crashes and demonstrated a tendency for expected crashes to begin to decline above a threshold value; however, the causes of this relationship were unknown. The SPFs were used in several ranking methods, including SPF-predicted crashes, empirical Bayes estimated crashes, and potential for safety improvement, to aid in prioritization of locations that might have been candidates for safety improvement but that had not necessarily experienced a high frequency of crashes. On the basis of this example, this approach is feasible for jurisdictions that wish to be more proactive in addressing potential crashes and injuries. Jurisdictions must, however, begin routinely collecting the data needed to implement the method efficiently.