Evaluation of driver braking performance to an unexpected object in the roadway

Due to the character of the original source materials and the nature of batch digitization, quality control issues may be present in this document. Please report any quality issues you encounter to digital@library.tamu.edu, referencing the URI of the item.Includes bibliographical references.Stopping sight distance (SSD) design values are a major influence in the geometric design of horizontal and vertical alignment. The current SSD equation, developed by the American Association of State Highway and Transportation Officials (AASHTO) in 1940, incorporates two components into geometric design, a perception-response time (PRT) component and a braking distance component. Because of the importance of sight distance on highways, previous research has questioned the assumptions of these two components, specifically whether the equation accurately reflects driver and vehicle behaviors during a braking maneuver. This research evaluated the two components of the SSD equation. Four field studies were conducted that evaluated driver braking performance to an unexpected object, as well as for expected object conditions, to better quantify perception response times, braking distances, and deceleration characteristics for these two conditions. The effects of pavement conditions and different geometry sections, as well as the effects of antilock brakes, were also evaluated. Results of the research indicated that nearly all drivers can respond faster than the 2.5 second factor in the AASHTO perception-response time component. Furthermore, the results indicated that nearly all drivers can perform a braking maneuver, on wet and dry pavements, in a shorter distance than the derived value of the AASHTO braking distance component. The results of the research also indicated that drivers do not perform locked-wheel braking maneuvers, but rather, controlledtype maneuvers by modulating the pressure applied to the brake pedal