Continuous visual evaluation of headway between motor vehicles - using width of image of preceding vehicle seen through graduated arcuate triangular diagram in fixed position

摘要

The diagramis printed on a transparent sheet fixed to a vertical windscreen or attached by hinged suckers to a sloping one, at a known distance (taken as 45 cm) from the driver's eyes. Graduations (V1-V4) represent distances at which the image of a preceding vehicle of average width (taken as 1.65m) will appear to extend from one side of the arcuate triangle to the other. The values (22,33,50 and 67m) are chosen as corresp. to 'safe' headways of two seconds at traffic speeds of (40,60,90. and 120 km/hr) respectively.