01020677

Component

https://doi.org/10.3141/1931-14

http://scholar.google.com...wley&publication_year=2005

This paper describes research sponsored by the Texas Department of Transportation to investigate the operational and safety impact of raised medians and driveway consolidation. Operational effects (travel time, speed, and delay) were investigated through microsimulation on three field test corridors and three theoretical corridors. Safety effects were investigated along 11 test corridors to estimate relationships between crash rates and access point densities as well as the presence of raised medians or two-way left-turn lanes (TWLTLs). The research demonstrates that access management effects are case specific and that microsimulation can assess these unique operational effects. For the case studies investigated, replacing a TWLTL with a raised median resulted in an increase in travel time on two test corridors and a decrease on one test corridor. Small increases in travel time were found with the theoretical corridors as well. The travel time differences are based on the traffic level and location and number of the raised median openings. When present, the relatively small increases in travel time, and subsequent speed and delay, appear to be outweighed by the reduction in the number of conflict points and increased safety. Detailed crash analysis on 11 test corridors indicated that as access point density increases, crash rates increase. This trend holds regardless of the median type. For test corridors in which crash data were investigated before and after the raised median installation, a reduction in the crash rate was always found. Finally, future research needs are identified, including the need to investigate operational and safety impact over a broader range of geometric conditions and longer corridors than investigated here.

01020675

English

pp 108-116

2005

Transportation Research Record: Journal of the Transportation Research Board

0309094054

Print

Figures (1) ; References (14) ; Tables (4)

Access control (Transportation); Before and after studies; Case studies; Crash rates; Driveways; Highway operations; Highway safety; Median openings; Microsimulation; Traffic delays; Traffic speed; Travel time; Two way left turn lanes

Driveway density; Future research; Raised medians

Oklahoma; Texas

Design; Highways; Safety and Human Factors; I20: Design and Planning of Transport Infrastructure; I81: Accident Statistics

TRIS, TRB, ATRI

Mar 24 2006 1:25PM

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