Some Effects of Road, Truck and Headlamp Characteristics on Visibility and Glare in Night Driving

Differences in characteristics between automobiles and trucks, such as driver eye height and headlamp mounting height, were examined, as well as roadway vertical and horizontal curvature and meeting beam patterns and lamp aim. Effects of these variables were evaluated by a computer simulation of nighttime meetings on a 2-lane road. The visibility distance and direct and indirect (mirror) glare discomfort effects were measured.

Results suggest that: low beam headlamps on trucks should not be mounted at more than about 36 in (0.91 m) from ground level, the increase in visibility provided by the mid beam is less for truck drivers than those of automobiles, the mid beam is less affected by vertical aim variations than the low beam, the mid beam should be extinguished by the vehicle in the inside lane on curves when meeting other vehicles and when following another vehicle at less than about 200 ft (61 m).