00799054

Component

https://doi.org/10.3141/1701-02

http://scholar.google.com...rick&publication_year=2000

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% of that level. Overall, drivers generated maximum decelerations from 6.9 to 9.1 m/sq s. The equivalent constant deceleration also varied among drivers. Based on the 90-km/h data, 90% of all drivers without ABS chose equivalent constant decelerations of at least 3.4 m/sq s under wet conditions, and 90% of all drivers with ABS chose equivalent constant deceleration of at least 4.7 m/sq s on dry pavements.

This paper appears in Transportation Research Record No. 1701, Design Speed, Operating Speed, and Sight Distance Issues.

English

p. 9-16

2000

Transportation Research Record

0309066808

Figures (2) ; Photos (1) ; References (10) ; Tables (6)

Antilock brake systems; Braking performance; Deceleration; Dry weather; Geometric design; Highway design; Human subject testing; Speed; Stopping sight distance; Wet weather

Horizontal curvature

Design; Highways; Planning and Forecasting; Safety and Human Factors; I21: Planning of Transport Infrastructure

TRIS, TRB, ATRI

Sep 29 2000 12:00AM

• DESIGN SPEED AND OPERATING SPEED IN RURAL HIGHWAY ALIGNMENT DESIGN
• DETERMINING THE BEST METHOD FOR MEASURING NO-PASSING ZONES
• EVALUATION OF THE PASSING PROCESS ON TWO-LANE RURAL HIGHWAYS
• GEOMETRIC DESIGN OF LOW-SPEED URBAN STREETS
• MATHEMATICAL MODELS OF VEHICULAR SPEED ON MOUNTAIN ROADS
• NEW STOPPING SIGHT DISTANCE MODEL FOR USE IN HIGHWAY GEOMETRIC DESIGN
• OPERATING SPEED ON CREST VERTICAL CURVES WITH LIMITED STOPPING SIGHT DISTANCE
• RELIABILITY APPROACH TO INTERSECTION SIGHT DISTANCE DESIGN
• SAFETY EFFECTS OF LIMITED STOPPING SIGHT DISTANCE ON CREST VERTICAL CURVES
• SIGHT DISTANCE FOR STOP-CONTROLLED INTERSECTIONS BASED ON GAP ACCEPTANCE
• SPEED REDUCTION AS A SURROGATE FOR ACCIDENT EXPERIENCE AT HORIZONTAL CURVES ON RURAL TWO-LANE HIGHWAYS
• SPEED-PROFILE MODEL FOR A DESIGN-CONSISTENCY EVALUATION PROCEDURE IN THE UNITED STATES
• SUMMARY OF DESIGN SPEED, OPERATING SPEED, AND DESIGN CONSISTENCY ISSUES
• TRUCK SPEED PROFILES