Improving safety and traffic operations in urban zones with a high propensity for rear-end collisions at signalized intersections

At signalized intersections, rear-end accidents are frequently the predominant accident type. These accidents result from the combination of a lead-vehicle's decelereation and the ineffective response of the following vehicle's driver to this deceleration. The frequency and severity of rear end collisions can be reduced through traffic control and operational improvements. There are different traffic operation strategies for rear-end collision reduction like "Employ multiphase signal operation". "optimize clearance intervals" or "Restrict or eliminate turning maneuvers (including right turns on red)". In practice, the most cost-effective strategy appears to be "Employ Signal Coordination". The first objective of this research report was to use spatial analysis tools to disaggregate Toronto into 76 spatial zones (Toronto is usually divided into 158 zones). The second objective was to rank the 76 zones according to their propensity for rear-end collisions at 4-legged signalized intersections. The third objective was to demonstrate how safety can be improved through signal coordination and progression. The software package Synchro-4.00 was used to recommend improved signal coordination through optimization of cycle lenghts, splits and offsets. The coordination analysis for the 15 intersectins located in the zone with the highest propensity for rear-end collision revealed the following results. 1. Coordination was definitely not recommended for three of the intersections. 2. Coordination was probably not recommended for six of the intersections; and 3. Coordination was definitely recommended for six of the intersections. The coordinatability analysis for the 15 intersections located in the zone with the highest propensity for rear-end collisions was performed on the basis of current cycle length (based on field observations). At the nine intersection where coordination is either definitely not recommended or probably not recommended, current cycle length needs to be optimized.

Improving safety and traffic operations in urban zones with a high propensity for rear-end collisions at signalized intersections

At signalized intersections, rear-end accidents are frequently the predominant accident type. These accidents result from the combination of a lead-vehicle's decelereation and the ineffective response of the following vehicle's driver to this deceleration. The frequency and severity of rear end collisions can be reduced through traffic control and operational improvements. There are different traffic operation strategies for rear-end collision reduction like "Employ multiphase signal operation". "optimize clearance intervals" or "Restrict or eliminate turning maneuvers (including right turns on red)". In practice, the most cost-effective strategy appears to be "Employ Signal Coordination". The first objective of this research report was to use spatial analysis tools to disaggregate Toronto into 76 spatial zones (Toronto is usually divided into 158 zones). The second objective was to rank the 76 zones according to their propensity for rear-end collisions at 4-legged signalized intersections. The third objective was to demonstrate how safety can be improved through signal coordination and progression. The software package Synchro-4.00 was used to recommend improved signal coordination through optimization of cycle lenghts, splits and offsets. The coordination analysis for the 15 intersectins located in the zone with the highest propensity for rear-end collision revealed the following results. 1. Coordination was definitely not recommended for three of the intersections. 2. Coordination was probably not recommended for six of the intersections; and 3. Coordination was definitely recommended for six of the intersections. The coordinatability analysis for the 15 intersections located in the zone with the highest propensity for rear-end collisions was performed on the basis of current cycle length (based on field observations). At the nine intersection where coordination is either definitely not recommended or probably not recommended, current cycle length needs to be optimized.

Assessment of a Displaced Pedestrian Crossing for Multilane Arterials

This research explores the benefits of a pedestrian crosswalk that is physically displaced from the intersection, using simulation software to estimate the benefits in terms of delay and pedestrian travel time. In many cases, the displaced pedestrian crossing may provide benefits such as reduced vehicle delay, reduced crossing distance, increased opportunity for signal progression, and reduced conflicts with turning vehicles. The concurrent pedestrian service that is traditionally used presents potential conflicts between pedestrians and three vehicular movements: right turns, permissive left turns, and right turns on red. The findings of this research suggest that a displaced pedestrian crossing should be considered as an option by designers when serving pedestrians crossing multi-lane arterials. In addition to reduced delay, pedestrian safety may be improved due to the shorter crossing distance, the elimination of conflicts with turning vehicles, and the potential for high driver compliance rates associated with signals, such as pedestrian hybrid beacons.

Inattention and Misjudgment in Older Drivers Involved in Automobile Collisions in Hawai'I, 1986–1991

Motor vehicle collision reports filed by police officers may be useful in investigating driver behavior and identifying potential causal attributes of accident involvement. Inattention and misjudgment were two options appearing on police reports to explain the cause of motor vehicle collisions in Hawai'i from 1986 to 1991. Examination of all crash reports (n = 218,718) revealed that inattention and misjudgment are serious problems for older drivers (65 years and older, n = 14,179). For instance, for the 75 to 84 year old drivers involved in collisions (n = 3659), 36% were classified as inattentive and 22% were identified as having misjudgment errors in driving; for the 85 and older drivers (n = 340), these percentages were 41 and 22, respectively. Of the collisions involving older drivers, 48% were at intersections. Reports of inattention and misjudgments were highest at dusk and dawn compared to other times of the day and night. Among the rear-end collisions, 65% of the older rear-enders were inattentive drivers. Strong associations of inattentive older drivers were found with being a broadsider (49%), side-swiper (45%) and headoner. Misjudgments among older drivers were most associated with being a side-swiper (41% from the opposite direction and 37% from the same direction). Regarding vehicle maneuvers prior to the crash, inattention was associated with right turns on red (61%), U-turns (57%), starting from park (56%), backing (56%), changing lanes (48%), merging (45%), and making left turns (40%). Misjudgment errors were most likely to occur when overtaking (44%), parking (41%), making left turns (39%), and changing lanes (39%). Dangerous actions common among inattentive older drivers included disregarding traffic controls (72%), following too closely (67%), going the wrong way (54%), failing to yield (52%), improper turns (48%), and speeding (45%). Older drivers classified as having misjudgments were most likely to be involved in improper overtaking (46%), failure to yield (41%), and improper turns (39%).

Estimation of right turn on red saturation flow rates

It is common practice in most Canadian provinces to permit right turns on red at signalized intersections. At intersections with a high volume of pedestrian traffic, the opportunity to turn right on red may be critical to satisfy right turn demand. However, in order to properly time the traffic control signal display at a signalized intersection, the saturation flow rates for each lane or lane group of the intersection must be known. Six signalized intersections were studied in Kingston, Ontario, where saturation flow rates for right turns were measured as a function of conflicting through traffic. From these measurements, estimations of the gap size required for a right turn movement were made. A regression analysis resulted in the production of a simple equation for estimating right turn on red saturation flow rates. It was found that the gap acceptance behaviour of drivers varied both spatially and temporally. Key words: saturation flow rates, signalized intersections, capacity, gap acceptance.