Citation

Squires CA, Parsonson PS. Transp. Res. Rec. 1989; 1239: 30-40.

Copyright

(Copyright © 1989, Transportation Research Board, National Research Council, National Academy of Sciences USA, Publisher SAGE Publishing)

DOI

unavailable

PMID

unavailable

Abstract

It is accepted that the installation of a median will reduce accident occurrence along a previously undivided road. This report provides an accident comparison of raised medians and continuous two-way left-turn lanes used as median treatments on four- and six-lane roads. A statistical comparison of accident rates for the two section types and regression equations to model expected accident experience for each section were developed. Four- and six-lane roadway study sections in Georgia were analyzed separately. The accident rate of raised medians was found to be lower than the rate of two-way left-turn lanes for both four- and six-lane roadway sections. Regression equations were developed for raised median and two-way left-turn lane sections, four- and six-lane sections, total and midblock accidents, and accidents per million vehicle miles and accidents per mile per year. Tables of expected accident rate values were developed from the regression equations. On the basis of expected total accidents per million vehicle miles the tables indicated that for four-lane sections, raised medians had a lower accident rate over the range of data studied.

RESULTS from six-lane sections were mixed. The regression equations indicated that raised medians would have lower accident rates for most conditions. However, two-way left-turn lanes had a lower accident rate where few concentrated areas of turns, such as signalized intersections and unsignalized approaches, existed.

Record URL:
http://onlinepubs.trb.org/Onlinepubs/trr/1989/1239/1239-005.pdf

Language: en

Keywords

Roads and Streets; Statistical Methods--Regression Analysis; Highway Accidents--Analysis; Highway Systems--Median Dividers