Safety Implications of Truck/Car Speed Limits for Two-Lane Highway Operations
The safety implications of car-truck speed limits have not been adequately researched, and this has been especially true for two-lane highways. On two-lane highways speed controls can have a significant effect on rear-end and head-on vehicle interactions. This paper uses simulation to assess the effect on safety of different speed control strategies applied to two-lane highway operations. Two different types of speed control strategies are considered: uniform speed limit (USL) and car-truck differential, which is introduced in two different ways: discretionary differential car and truck posted speed limits (DSL) and mandated truck speed limiters (MSL). Safety implications are considered using three overtaking-related indicators: 1) number of vehicles overtaking; 2) percentage time spent in “desire to overtake mode” (PTDO); and 3) average Time-to-Collision (TTC) with the on-coming vehicle prior to returning back to the original lane. Vehicle interactions affecting safety are estimated through the application of a calibrated microscopic traffic simulation model to a 6Km straight segment of two-lane highway with zero and -3% grade. Differential speed strategies (DSL and MSL) were observed to have a slight increase in the total number and rate of overtaking maneuver in comparison to the uniform control strategy (USL). DSL strategies significantly increased the number and rate of car-truck overtakes over the range of volumes considered in the simulation, suggesting a negative effect on safety. At the same time the number of car-car overtakes were reduced suggesting a positive effect on safety. No considerable effects were observed concerning differential speed control strategies and average TTC and PTDO for the studied cases. The number of overtakes were found to be higher on the level segment than the downgrade segment for the control strategy; although, not very significant for MSL. Car-car and car-truck overtakes appeared to be consistently higher in level section than the grade section; however, this was opposite where the MSL strategy was considered.
-
Supplemental Notes:
- This paper was sponsored by TRB committee ANB20 Safety Data, Analysis and Evaluation.
-
Corporate Authors:
500 Fifth Street, NW
Washington, DC United States 20001 -
Authors:
- Ghods, Amir H
- Saccomanno, Frank
-
Conference:
- Transportation Research Board 92nd Annual Meeting
- Location: Washington DC, United States
- Date: 2013-1-13 to 2013-1-17
- Date: 2013
Language
- English
Media Info
- Media Type: Digital/other
- Features: Figures; References; Tables;
- Pagination: 16p
- Monograph Title: TRB 92nd Annual Meeting Compendium of Papers
Subject/Index Terms
- TRT Terms: Automatic speed control; Highway safety; Passing; Speed limits; Two lane highways
- Subject Areas: Highways; Motor Carriers; Operations and Traffic Management; Safety and Human Factors; I73: Traffic Control; I82: Accidents and Transport Infrastructure;
Filing Info
- Accession Number: 01477631
- Record Type: Publication
- Report/Paper Numbers: 13-2329
- Files: TRIS, TRB, ATRI
- Created Date: Apr 8 2013 9:34AM