Driver Braking Performance in Stopping Sight Distance Situations

Abstract

Assumed driver braking performance in emergency situations is not consistent in the published literature. A 1955 study stated that in an emergency situation “it is suspected that drivers apply their brakes as hard as possible.” This idea differs from a 1984 report that states drivers will “modulate”their braking to maintain directional control. Thus, additional information is needed about driver braking performance when an unexpected object is in the roadway. In this research driver braking distances and decelerations to both unexpected and anticipated stops were measured. The study design allowed for differences in vehicle handling and driver capabilities associated with antilock braking systems (ABS), wet and dry pavement conditions, and the effects of roadway geometry. Vehicle speeds, braking distances, and deceleration profiles were determined for each braking maneuver. The research results show that ABS result in shorter braking distances by as much as 30 m at 90 km/h. These differences were most noticeable on wet pavements where ABS resulted in better control and shorter braking distances. Braking distances on horizontal curves were slightly longer than on tangent sections; however, they were not large enough to be of practical significance. Maximum deceleration during braking is independent of initial velocity, at least in the range of speeds tested. Differences were noted in individual driver performance in terms of maximum deceleration. Although maximum deceleration was equal to the pavement’s coefficient of friction for some drivers, the average maximum deceleration was about 75 percent of that level. Overall, drivers generated maximum decelerations from 6.9 to 9.1 m/s2. The equivalent constant deceleration also varied among drivers. Based on the 90-km/h data, 90 percent of all drivers without ABS chose equivalent constant decelerations of at least 3.4 m/s2 under wet conditions, and 90 percent of all drivers with ABS chose equivalent constant deceleration of at least 4.7 m/s2 on dry pavements.

A farewell to brake reaction times? Kinematics-dependent brake response in naturalistic rear-end emergencies

“…From some controlled studies, there are also reports of progressive or step-wise ramping up towards these maximum levels (Prynne and Martin, 1995;Fambro et al, 2000b;Lee et al, 2002). Again, a detailed, quantitative account of emergency braking control is lacking, especially for naturalistic data.…”

“…As for what happens beyond the point of brake onset, it has been reported from both controlled and naturalistic studies that drivers will often, but not always, show maximum deceleration levels close to their vehicle's limits on the given road (McGehee et al, 1999;Fambro et al, 2000b;Lee et al, 2007). From some controlled studies, there are also reports of progressive or step-wise ramping up towards these maximum levels (Prynne and Martin, 1995;Fambro et al, 2000b;Lee et al, 2002).…”

A microscale evaluation of pavement roughness effects for asset management

“…By equating those distances, it was possible to simulate constant fuel consumption throughout the entire test sections (knowing that the vehicle is moving at constant speed throughout 90% of the test sections). The applied acceleration and deceleration rates were well below the respective maximums noted in the literature by Rakha et al (2004) and Fambro et al (2000).…”

Look at Me

“…response, maximum deceleration) and final outcome of vehicle measures (e.g., stopping distance, time to stop) [7,14]. Braking behavior can be further modeled and characterized into normal or hard braking by analyzing deceleration profiles (changes in headway, speed and acceleration during braking maneuver) [6,16].…”