Study Details
Study Title: Impacts of Exit Ramp Type on the Safety Performance of Freeway Diverge Areas
Authors: Chen et al.
Publication Date:JAN, 2008
Abstract: This study evaluated the impacts of exit ramp types on the safety performance of freeway diverge areas. Crash data were collected at 423 freeway segments in various locations throughout the State of Florida. The selected sites were divided into four groups based on the types of the exit ramps. In this study, exit ramp types were defined based on the number of lanes used by vehicular traffic to exit freeways. The exit ramp types considered here include single-lane exit ramps, sing-lane exit ramps without a taper, two-lane exit ramps with an optional lane, and twolane exit ramps without optional lane. For convenience, they were defined as type 1, type 2, type 3, and type 4 exit ramps respectively. Cross-sectional comparison was conducted for comparing crash frequency, crash rate and crash severity between different exit ramp types. A crash prediction model was developed to identify the factors that contribute to the crashes that have been reported for selected freeway segments and to quantify the safety impacts of different freeway exit ramps. The crash data analysis results show that the type 1 exit ramp has the best safety performance in terms of the lowest crash frequency and crash rate at freeway diverge areas. For one-lane freeway exit ramp, replacing a type 1 exit ramp with a type 2 exit ramp will increase crash counts at freeway diverge areas by 12.8%. For two-lane exit ramps, replacing a type 3 ramp with a type 4 ramp will increase crash counts at freeway diverge areas by 11.7%.
Study Citation: Chen, H., Liu, P., Behzadi, B., Lu, J.J. "Impacts of Exit Ramp Type on the Safety Performance of Freeway Diverge Areas." TRB 87th Annual Meeting Compendium of Papers CD-ROM. Washington, D.C., 2008.
CMFs Associated With This Study
Category: Interchange design
Countermeasure: Single-lane exit ramp without taper (right ramp only)
| CMF | CRF(%) | Quality | Crash Type | Crash Severity | Roadway Type | Area Type |
|---|---|---|---|---|---|---|
| 1.128 | -12.8 |  | All | All | Principal Arterial Other Freeways and Expressways |
