Accident Characteristics Before, During, and After Safety Upgrading Projects on Ohio’s Rural Interstate System

In 1973, minor safety upgrading projects were conducted at 21 locations on the rural Interstate system of Ohio, involving 618 km (384 miles) of freeways. In 1972, the accident rate per million vehicle kilometers ( MVKM) on these 618 km was 112.9 accidents/161 MVKM (112.9/100 million vehicle miles). In 1974, the accident rate dropped to 77.9 accidents/ 161 MVKM. To account for the possible effect of the introduction of the reduced speed limit in 1974, accident rates were also compared on 246 km (153 miles) of the rural Interstate system not subjected to safety improvement. The difference inproportional reduction in accident rates is statistically significant and favors the 21 study sites. The accident rates increased to 120.8 accidents/161 MVKM during the 1973 safety upgrading construction program. However, only 151 accidents were positively identified from traffic crash reports and construction diaries as construction related. These 151 accidents were studied in detail. Observed patterns included: (a) rear-end (61) and single vehicle, fixed-object (56) accidents were the most frequent; (b) 34 accidents occurred in the relatively short taper area; (c) the proportion of the lane taper accidents at night and at dawn or dusk was high; (d) the proportion of construction object accidents at night was high; (e) the proportion of tractor-trailer and bus accidents at night was high; (f) excess speed was listed in 88 cases as a contributing factor, while road defects or construction or traffic control were listed only in 15 cases. Some suggestions are being made regarding traffic control at work zones.