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production. All correlations were significant (p < 0.01; N=132), indicating high correlations between stimuli and the estimated or assigned magnitude. 3.3.3iscussfon

With magnitude estimation, the rank order of all median estimates of force and angle increased with of growth production apparent force using magnirude estimatml of apparent force using magni

Data from 12 subjects Incresing force and angle, except for the middle (100 and 120) force estimates. This deviation is assumed to have arisen by chance. To assess the impact that this deviation has on the exponent obtained from the median data, an exponent was regressed to all data points from all subjects. This yielded an exponent of 1.14, which is the same as the exponent determined from the median data. Similarly, with magnitude production, the median forces and angles

increased with increasing required value, except for the two lowest forces. The lowest median force was produced when subjects were asked to produce a rate of growth of sensation of apparent force and angle is taken as the geometric mean of the rates of growth for magnitude estimation and magnitude production. In this study, the means of the esti- mation and production slopes were 1.39 for steeringwheel force and 0.93 for steering-wheel angle.

The rate of growth of sensation of steering wheel force ties within the range previously reported for force. A rate of growth of 1.39 means the sensation of force growmore rapidly than the force causing the sensation. For example, a doubling of force will give rise to a 162 per cent increase in the perception of force. Steering-wheel angle had a mean rate of growth of 0.93; so the sensation of angle grows at a slower rate than the angle. For example, a doubling of angle would give rise to only a 91 percent increase in the perception of angle force corresponding to an apparent magnitude of 70'; the median force was slightly higher (although not significantly different) for apparent magnitudes of '60' and '50'. This deviation from the expected order, which is assumed to have arisen chance means that the exponent for force production (1.70) was higher than it would have been without the two lowest forces. Regression to all the data from all subjeers for force production (instead of the median judgement) yielded an exponent of 1.38

The regression effect was present in both the force and the angle data. An estimate of the 'unbiased' Although it is desired to optimize 'steering feel', there has been little systematic investigation of what drivers feel, the differences that they can detect, or the way that sensations change with variations in force or angle of turn of steering wheels. The first experiment addressed the appropriate terminology for steering feel, in anticipation of the subsequent two studies. The results of the first study imply that the hotic properties of steering systems in vehicles should take account of the radius of the steering wheel when considering the load applied by the driver. Variations in the steering-wheel radius will scale