An evaluation of an in-vehicle headway feedback system with a visual and auditory interface

Postans and Wilson (1983) observed that on the Bedfordshire stretch of the M1 motorway the most frequent cause of personal road accident injuries between 1976-1979 was the rear-end shunt. Tailgating is cited as the primary contributory factor in rear-end shunts. It has been proposed that larger headways will reduce the number of road accident injuries incurred and commonly recommended that a time headway (TH) of 2 seconds is employed. Other studies have shown that this recommendation is frequently ignored. The work described involved a controlled experimental study to (a) determine the effects of providing continuous time headway feedback on driving behaviour and (b) evaluate the actual interface employed. The findings of the study suggest that while the use of a TH feedback system may decrease the TH adopted by a driver, these behavioural changes are likely to be a reaction to the system implemented, and not so much a general adoption of increased THs. Results suggest that a system as described above may be generally accepted by drivers, but the implications of the likely cost of the system are unclear. In terms of reducing adopted time headways, its practical value may be limited in traffic conditions where focused attention occurs or a degree of social pressure is imposed upon the driver. As a learning device, these initial findings indicate that such a system may not be particularly effective.