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It is important for large trailers to be outlined with retroreflective tape to make them more conspicuous in roadway environments with diminished ambient lighting. Retroreflective material is also utilized on signs as well as clothing to improve their conspicuity. As used conspicuity tape does not perform at the same level as clean and new tape. Hence, there is a need for visibility testing of retroreflective materials with degraded or reduced effectiveness. In an effort to control the coefficient of retroreflection (RA). A methodology that uniformly obscured parts of the retroreflective materials was developed. Validation testing of this procedure was conducted using glass bead sheeting, as well as microscopic prismatic sheeting. The results from the study showed that, by uniformly obscuring parts of the tape, RA is approximately a linear function of the area exposed to the viewer. Thus, the overall perceived brightness and coefficient of retroreflection readings were reduced.

Rear-end crashes account for more than one in five fatal crashes in the U.S. The rear-end crash scenario most commonly associated with fatal crashes involves a following vehicle traveling 40 to 70 mph closing on a lead vehicle at a rate greater than 30 mph. The current research compiled an analysis of the literature to identify the kinematic factors, environmental factors, traffic-related factors and individual differences that are likely to influence drivers’ responses when closing on a slower-moving or stopped lead vehicle [LV]. In Part 1, several primarily kinematic-based methods for modeling drivers’ responses to a LV were compared for high-speed closing events. Methods utilizing looming (angular growth rate) equations were shown to predict drivers’ responses and time-to-contact methods (Inverse Tau) were conditionally accurate when applied to specific crash scenarios. However, the ratio or nominal response time methods did not predict drivers’ responses in most crash scenarios.

Analyses of driver response time studies and fatal crash statistics were examined to determine: 1. whether all rear-end crash types can be analyzed as one crash type, 2. average braking thresholds for drivers, and 3. the influence cell phone usage has on drivers’ response times when responding to a lead vehicle. The goal of this research is to recommend protocols for investigating LV crashes that is supported by the literature. Two distinct lead vehicle [LV] response time events emerged: LV platoon (two vehicles traveling together in close proximity) and LV looming (a vehicle approaching a stopped or much slower LV). In normal driving, platoon LV events were very common but resulted in very few crashes per exposure. Young drivers were over-represented when they did occur. Onset of the hazardous event was when the LV decelerated, and drivers began braking roughly 3 to 5 seconds before impact.

The turn-across-path from opposite-direction [LTAP-OD] crash type contributes to one of the major fatal crash types in young drivers. Drivers responses in police reportable and severe crashes and near crashes involving an LTAP-OD scenario were evaluated from query of the Second Strategic Highway Research Program [SHRP-2]. This research examined the responses of through drivers. 122 such events were analyzed to extract driver braking behavior, secondary tasks, age, and perception-response times. All measures of through driver variables were compared with respect to turning driver behavior. The study aimed to identify the trigger event for drivers to respond to the left turning vehicle. Time to contact was a significant factor which affected driver response times. Drivers responded significantly faster when subjected to shorter time to contact events compared to longer ones.

Collision statistics show that more than half of all pedestrian fatalities caused by vehicles occur at night. The recognition of objects at night is a crucial component in driver responses and in preventing nighttime pedestrian accidents. To investigate the root cause of this fact pattern, Richard Blackwell conducted a series of experiments in the 1950s through 1970s to evaluate whether restricted viewing time can be used as a surrogate for the imperfect information available to drivers at night. The authors build on these findings and incorporate the responses of drivers to objects in the road at night found in the SHRP-2 naturalistic database. A closed road outdoor study and an indoor study were conducted using an automatic shutter system to limit observation time to approximately ¼ of a second. Results from these limited exposure time studies showed a positive correlation to naturalistic responses, providing a validation of the time-limited exposure technique.