Citation

Michaels RM. Highw. Res. Board bull. 1960; 271: 29-44.

Copyright

(Copyright © 1960, National Research Council (U.S.A.), Highway Research Board)

DOI

unavailable

PMID

unavailable

Abstract

The present study was an attempt to relate driver tension responses to those events in traffic which caused an overt change in speed or lateral location of a test vehicle. In order to measure tension responses the galvanic skin reflex (GSR) was employed, and measurements were made continuously during each trip along two urban streets. Traffic events influencing the test vehicle were determined independently by an observer and recorded on the gsr record. The traffic events were restricted to eight possible interferences, which accounted for 95 percent of all agents causing a change in test vehicle speed and placement. Ten driver subjects were used on the two test routes. Runs were made during five time periods, including peak, offpeak, and night. Each subject drove the test route 25 times, distributed over a two-week period. The results indicated that traffic events occurred, depending upon the street, at a rate of one every 21 to 35 seconds. Of these, 85 percent generated a measurable GSR response. Depending upon the street, the majority of responses were caused by other vehicles in the traffic stream, accounting for 60 percent or more of all events. The events which generated the greatest mean tension response were those involving a maximum difference in speed between the object and test vehicle. Thus, turning maneuvers and crossing and merging were most tension inducing. The least stress inducing events were related to fixed objects in the environment, such as parked vehicles or islands. This ordering was statistically reliable among the subjects. Using the magnitude of GSR response per unit of time as an over-all measure of driver tension, it was possible to compare the two test routes. It was found that the route subjectively preferred by drivers induced an average of 40 percent less tension response per minute than did the other route. An analysis of variance showed that these differences between routes were statistically significant. The results of this study indicate that a road generates tension in drivers inversely with the predictability of the interferences and directly with the complexity of the traffic situation with which they must deal. In addition, the magnitude of tension response is directly related to the rate at which decisions are forced upon the driver by the traffic.