Study Details
Study Title: Evaluation of the Impacts of Differential Speed Limits on Interstate Highways in Idaho
Authors: Dixon et al.
Publication Date:OCT, 2012
Abstract: In this research, an evaluation of the impacts of differential speed limits on rural interstate highways in Idaho was completed. The main purpose for this research was to determine if there have been any speed or safety effects after enacting the DSL, and also to study some of the geometric effects, like rumble-strips, on the safety of vehicles on rural Idaho interstates. Regarding the effects of DSL on speed, it was found that passenger car and truck speeds stabilized since the DSL policy implementation date. More specifically, the DSL reduced truck speeds, resulting in mean passenger vehicle and truck speeds of 74.7 and 65.6 mph, respectively. Regarding the DSL effect on speed compliance, Passenger vehicle compliance slightly worsened, while truck compliance improved. Establishment of the DSL policy also contributed to a decrease in the crash rates on Idaho's rural interstates.
Study Citation: Dixon, M., A. Abdel-Rahim, S. Elbassuoni. "Evaluation of the Impacts of Differential Speed Limits on Interstate Highways in Idaho." Report No. FHWA-ID-13-218. Idaho Transportation Department. (Oct. 2012)
Study Report: Download the Study Report Document
CMFs Associated With This Study
Category: Speed management
Countermeasure: Install 10 mph differential speed limit on rural Interstate Highways
| CMF | CRF(%) | Quality | Crash Type | Crash Severity | Roadway Type | Area Type |
|---|---|---|---|---|---|---|
| 0.914 | 8.56 |  | All,Truck related | All | Principal Arterial Interstate | Rural |
