Analysis of Injury Severity in Crashes on Ramps and at Crossroad Ramp Terminals
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Travel along a ramp can presuli drivers with complex alignment changes and decision points. These changes and complexities can increase the potential for conflict or crash, especially for larger vehicles. A few studies have examined the effect of variables on ramp crash frequency. However, none of these studies considered the effect of variables on crash severity distributions. Relatively little or no information is available about the safety effects of design elements on the severity of ramp crashes. In some cases, countermcasures (such as longitudinal barriers) arc implemented to reduce fatal crashes, but the effect of these treatments on less severe crashes is not well understood. New research has been conducted to develop severity distribution functions (SDKs) for ramp segments and signalized and unsignalized crossroad ramp terminals for predicting the proportion of crashes in each severity category as a function of roadway geometric design elements and traffic control features. The SDKs were calibrated with data from California, Maine, and Washington State. The findings from this research show that barrier presence, the number of through lanes, area type, and ramp type influence the proportion or high-severity crashes on ramp segments. At the same time, access point frequency, left-turn operation, the presence of nonramp public street leg, and area type influence the proportion of high-severity crashes at crossroad ramp terminals. These SDKs can be applied along with safety performance functions and crash modification factors to obtain more precise estimates of the safety effects of design decisions.
author list (cited authors)
Geedipally, S. R., Bonneson, J. A., Pratt, M. P., & Lord, D.