The author describes a macro-model that was established to study the impact on fatal accident rates in america of highway facilities and other important variables. Highway capacity is defined as the ratio of rated lane-miles of highways to the area of the region, the rating being dependent on access control, pavement width, curvature and gradient. Results indicated that accident rate decreased with increase in capacity; a 10 per cent increase in capacity yielding a 0.9 per cent decrease in accident rate per vehicle mile. Increase in speed limit was associated with an increase in accident rate (10 per cent increase yielding 4.5 per cent increase respectively). Accident rate was found to increase as temperature increased. Age was found to be negatively related to accident rate, suggesting that an increase in minimum driving age from 16 to 18 would be accompanied by a reduction of about 11.1 per cent in accident rate per vehicle mile. Age adjusted accident death rate was found to be 41.9 for males and 14.5 for females per 100000 population. Rates for non-metropolitan counties were higher than for metropolitan counties.
Abstract