The need for more push buttons and other finger or hand activated types of controls on automobile dashboards, steering wheels, stereos and in-car communication systems has increased over recent years. With designers reducing the button sizes and compacting them together, the driver is forced to devote more time and concentration to activate the correct buttons. This could impose many safety problems if too much time and concentration are diverted from the driving task. The objective of this study is to examine some of the human factors issues and their principles as they relate to the design of push buttons in terms of the shape, size and spacing. The first part of this study investigates a driver's accuracy when pushing buttons located at three different positions along the longitudinal center-line of the car, while either stationary or driving at approximately 20 mph. Our results show that for the conditions investigated a circular push button offers a nearly optimal design shape because the horizontal and vertical miss standard deviations proved to be approximately equal. Secondly, the middle or stereo position provided the greatest accuracy in each conditions. The second part of this study developed cumulative probability curves for hit rates as a function of the radius for each speed and position and combined this with index finger-tip dimensions to develop a design methodology. This methodology allows a designer to determine the size and spacing of push buttons to obtain a desired confidence of hitting the correct button while avoiding any inadvertent hits of adjacent buttons at a selected confidence level. (A)
Abstract