High approach speeds coupled with aggressive driving often lead to the running of red lights at intersections. When motorists see a yellow light as they approach an intersection, they are supposed to stop unless such sudden stopping is unsafe. Entering an intersection during the red signal is a citable offense, and several states are working to legalize video detection and enforcement using red light violation camera systems. Such enforcement is targeted toward driver behavioral modification; in the absence of an all-red interval the motorist who enters an intersection during the red signal runs an extremely high risk of being struck by cross-street traffic. A study was performed in the city of Detroit, Michigan, to compare the red light violation characteristics of intersections with properly designed all-red intervals and those intersections without all-red intervals. In the absence of before violation data, a comparative parallel experimental study was used. It was hypothesized that providing an all-red interval following a yellow change interval would reduce right-angle crashes. A before-and-after crash analysis was performed at the all-red-interval treatment sites (sites that targeted a reduction of right-angle and injury crashes). The analysis indicated significantly lower red light violations at the treatment sites. The analysis also indicated an extraordinary reduction in right-angle and injury crashes. This study demonstrated that substantial benefits, in terms of reducing red light violations and right-angle crashes, can be achieved by introducing a well-designed all-red interval.

Research was conducted to ascertain the validity of a driving simulator in determining the effectiveness of temporary traffic control devices in a work zone during nighttime hours. The research was conducted through a field study and a simulator study. The field study examined speeds at six sites and the simulator study utilized 127 human subjects. Spot speeds were observed at three locations in a freeway work zone. The location of the speed studies were at the beginning of the work zone near the transition area, in the middle of the work zone, and at the end of the work zone near the downstream taper. Statistical analyses were conducted to determine whether the participants of the study performed differently in the simulator, as compared to the field. Research results established that due to the motorist's perceived risk of work zones, driving simulators may not replicate mean speeds observed in the field.

Red-light violations (RLV) have been an ongoing concern to many engineering professionals, because a large portion of crashes that occur at signalized intersections involve red-light running and such crashes often result in injuries and fatalities. It has been estimated that in the United States, about 260,000 traffic crashes occur per year that involve drivers who run red lights, of which 750 are fatal. A before-and-after evaluation of the impacts in terms of RLV and late exits at signalized intersections was performed with a change and clearance interval calculated according to ITE guidelines. The study included three signalized intersections located in Oakland County, Michigan. RLV data were collected with video cameras at intersection approaches before and after implementation of the change, and clearance intervals were calculated according to ITE guidelines. The results of the before-and-after study on RLV indicated mixed results. At one of the study intersections, the RLV rates were reduced after the modified change and clearance intervals were installed. However, at the other two study locations, no significant differences were found in RLV rates in the before and after periods. The rates of late exits significantly decreased after installation of the test change and clearance intervals at all three study intersections. Therefore, the effects of implemented all-red clearance intervals were effective in reducing the opportunity and risk of late-exiting vehicles being exposed to oncoming traffic at the three study intersections.

A study was conducted to assess the effectiveness of countdown pedestrian signals on both pedestrian and motorist behaviors at 13 intersections in Peoria, Illinois. The variables tested in this study included the proportion of pedestrians who started crossing the street during the “Walk,” flashing “Don't Walk,” and steady “Don't Walk” intervals, as well as vehicular positions in the intersection with respect to the traffic signal indication (late in the yellow signal indication and after the red signal indication). A before-and-after study was used at three intersections at which the pedestrian countdown signals were installed. Additionally, five test intersections with countdown pedestrian signals were compared with five control intersections with traditional pedestrian signals. The traffic volumes, geometry, and adjacent land use at the control sites were similar to those at the test sites; however, the control sites did not have the countdown feature. The results of the study indicate that countdown pedestrian signals are effective in enhancing pedestrian safety. No evidence of increased risk-taking behavior of motorists while they were traversing the intersections with countdown pedestrian signals was observed.

In 2010, the Illinois Department of Transportation began implementing the flashing yellow arrow (FYA) at intersections operating with protected–permissive left-turn (PPLT) control. Research was conducted to evaluate the safety-effectiveness of FYAs at 86 intersections and 164 approaches in central Illinois. The effectiveness evaluation was performed with 3 years of before-and-after FYA installation crash data and the empirical Bayes method. In the before condition, the left-turn signals operated with a circular green display indicating the permissive interval of PPLT control using a five-section signal head. In the after condition, the FYA replaced the circular green display for the permissive interval of PPLT with a four-section signal head. Supplemental traffic signs were mounted on the mast arm adjacent to the left-turn signal at over half of the FYA installations. The results of the comprehensive safety evaluation of the FYA for PPLT control are presented. Analyses were also performed to assess the effects of the FYA supplemental signs and the effects of the FYA overall on two subsets of at-fault drivers: older drivers (age 65+) and younger drivers (age 16 to 21). The resulting mean crash modification factors for the targeted crash types ranged from 0.589 to 0.714. The findings of this research support the continued use of FYAs for PPLT control to improve safety at signalized intersections in central Illinois.