01373662

Component

A speed limit of 55 mph (88 km/h) is typically used on rural highways in the U.S. For locations where curbs are installed along these roadways, some transportation agencies have suggested the use of a reduced 45 mph (72 km/h) speed limit because, according to AASHTO, running into curbs at high speeds may cause significant vehicular damage and even severe injuries. However, it has also been argued that lowering the speed limit after the installation of curbs may cause confusion in drivers, who do not perceive the risk associated with the newly installed curbs and tend to operate their vehicles at the same, higher, speed as before. To better understand driver behavior on rural highways before and after curb installation and with different speed limits, researchers at the University of Tennessee conducted a series of experiments in two-lane and four-lane highways respectively on a high fidelity driving simulator. This paper presents the findings of the four-lane study and compares these to the results from the previous two-lane study. The scenario matrix consists of several dimensions including posted speed limit (45 and 55 mph, or 72 and 88 km/h), curb installation, lateral clearance between the edge of travel lane and the curb (2ft, 6 ft, and no- curb, or 0.6 m, 1.8 m, and no-curb), weather (clear and fog), traffic conditions in the next lane (1400 veh/hr and 400 veh/hr), etc. For each subject under different experimental scenarios, detailed driving parameters, such as driving speed and vehicle position in the travel lane, were recorded and analyzed subsequently. Results of the study suggest that driver behaviors are influenced by the various factors in a complex and interrelated manner. It is likely that drivers do not perceive the risk from the curb in determining their speed on four-lane rural highways. However, it is found that curbs may provide certain guidance to drivers, especially in selecting lane position. Comparing to the previous research in two-lane conditions, it is found that drivers are more likely to choose driving speeds according to posted speed limits, rather than roadway configurations. It is also found that the relative speed between driver’s vehicle and ambient traffic or curbs is an important factor determining drivers’ perception of risk and thus their driving behavior. The influence of subjective effects of these factors to their driving behavior is also observed in the study.

This paper was sponsored by TRB committee AHB65 Operational Effects of Geometrics

01362476

12-3294

English

18p

2012

Transportation Research Board 91st Annual Meeting

Digital/other

Figures; References; Tables

Behavior; Curbs; Drivers; Four lane highways; Highway safety; Rural highways; Speed; Speed limits; Two lane highways

Highways; Safety and Human Factors; I82: Accidents and Transport Infrastructure; I83: Accidents and the Human Factor

Transportation Research Board Annual Meeting 2012 Paper #12-3294

TRIS, TRB

Feb 8 2012 5:15PM