The evaluation of drivers responses to a multi-characteristic power assisted steering system

摘要

A sample of fifty male and fifty female drivers took part inan:. experiment designed to evaluate a multi-characteristicpower assisted steering system. Subjects drove a car fittedwith the system for two one-hour periods on public roads andon two test-track sessions during which a number of drivingperformance variables including driving time and steeringactivity were recorded. Drivers completed a speciallydeveloped questionnaire after each road drive. A subsidiarytask, which involved the visual monitoring of an illuminateddisplay and verbal responses, was administered during thetest-track sessions.Factor analysis and discriminant analysis were used toanalyse data from the questionnaire, road drives and test-track sessions. Data were first factor analysed and thefactors subsequently used as variables in the discriminantanalyses. It was possible to discriminate between male andfemale drivers, and between groups of drivers allocated tothe different power steering characteristics on the basis ofthe discriminant functions derived. Thus, reales were found tobe more sensitive to the force feedback characteristics ofthe standard power steering than females, finding it difficultto judge the amount of effort required to steer the car andtending to 'over steer' under some circumstances. Males drovefaster than the females on the Motorway with the standardpower steering, however, more slowly than females in urbandriving, and drove faster and more accurately than femaleson the test-track. On the basis of the differences observedbetween drivers allocated to the different power steeringcharacteristics, criteria were developed which allowed thespecification of that characteristic which could be considerec'optimal' for ordinary drivers of both sexes. This character-istic, termed "Speed Proportional Feel", provides the driverwith full power assistance at low speeds, but increasinglyinhibits the operation of the power assistance as vehiclespeeds rise, giving more steering 'feel' at high speeds. The test-track data were further analysed by means of theanalysis of variance and analysis of covariance. The resultsof the analysis of variance indicated that the presence ofthe subsidiary task had affected drivers' performance onthe test-track. Analysis of covariance was used to providea statistical control for the effects of the subsidiary taskon drivers' primary task performance and a significantlearning effect was observed. No significant differenceswere found in the number of subsidiary task responses madeby drivers allocated to different steering characteristics.A recommendation was made for further research into theobserved differences between males' and females' drivingspeeds which, it was suggested, may be related to the typesof accident in which males and females are typically involved.Further research into the level of artificial 'feel' favouredby male and female-drivers was also recommended on the basisof the finding that females appeared to respond more favour-ably to a lower level of 'feel' than males.