Safety Investigation of Combining Ramp Metering and Variable Speed Limits Strategies on Urban Freeways: A Simulation Study
Ramp metering and variable speed limits (VSL) are two intelligent transportation systems (ITS) strategies used to control traffic flow and speed on freeways. Combining both strategies can have the potential of improving safety on urban freeways; however, very few studies have investigated this safety potential. This study investigates the impact of combining both ramp metering and VSL on alleviating the rear-end and lane-change crash risks on a 36.25-mile stretch of Interstate-4 in Florida using the PARAMICS micro-simulation package. The study investigates the safety impact of this combination against the base scenario of non-implementing either strategy. Different scenarios were proposed, including the Zone and ALINEA ramp metering algorithms, and various speed zone and speed change time cases for VSL implementation. Three loading conditions were simulated; free-flow conditions, conditions approaching congestion, and congestion. Two primary measures of effectiveness (MOE) were used; safety and mobility. The safety MOE included two indices; the overall rear-end risk change index (ORERCI) and the overall lane-change risk change index (OLCRCI). The mobility MOE included the overall network travel time. The combination of ramp metering and VSL produced the most favorable safety benefits (for both ORERCI and OLCRCI) at free-flow conditions and at conditions approaching congestion, respectively. Furthermore, mobility-wise, there was a noticeable reduction in the network travel time when combining both strategies. The best case for implementing ramp metering in conjunction with VSL at free-flow conditions was using a speed change time of 5 minutes in conjunction with a 60-second cycle length for the Zone algorithm, and a 30-second cycle length for the ALINEA algorithm.
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Supplemental Notes:
- This paper was sponsored by TRB committee AND20 Standing Committee on User Information Systems.
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Corporate Authors:
500 Fifth Street, NW
Washington, DC United States 20001 -
Authors:
- Haleem, Kirolos
- Abdel-Aty, Mohamed
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Conference:
- Transportation Research Board 96th Annual Meeting
- Location: Washington DC, United States
- Date: 2017-1-8 to 2017-1-12
- Date: 2017
Language
- English
Media Info
- Media Type: Digital/other
- Features: Figures; References; Tables;
- Pagination: 18p
- Monograph Title: TRB 96th Annual Meeting Compendium of Papers
Subject/Index Terms
- TRT Terms: Crash causes; Ramp metering; Speed; Traffic flow; Travel time; Urban highways; Variable speed limits
- Geographic Terms: Florida
- Subject Areas: Highways; Safety and Human Factors;
Filing Info
- Accession Number: 01623640
- Record Type: Publication
- Report/Paper Numbers: 17-01045
- Files: TRIS, TRB, ATRI
- Created Date: Jan 25 2017 3:08PM