Truck Accidents at Freeway Ramps: Data Analysis and High-Risk Site Identification

To examine the relationship of ramp design to truck accident rates, this paper presents an analysis of truck accidents in Washington State, plus a comparison to limited data from Colorado and California. We group freeway truck accidents by ramp type, accident type, and by four conflict areas of each merge or diverge ramp. We then compare these groups on the basis of truck accidents per location and per truck-mile of travel. We found that truck accident frequencies and rates were not significantly different by ramp type alone, but were significantly different by conflict area and accident type, both between and within ramp types. We also found that high volume ramps had lower rates of truck accidents per truck-mile of travel. Thus, a ramp’s safety risk is related to accident type and conflict area, but not directly to truck volumes, which affects assessments of high-risk locations. Specifically, a ramp with few accidents but a high proportion of rollovers in the merge area may have a deficiency, or a ramp with a low accident rate per truck trip due to high truck volumes may still be a Truck Accidents at Freeway Ramps: Data Analysis and High-Risk Site Identification