00495451

Component

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

https://scholar.google.co...nson&publication_year=1989

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.

This paper appears in Transportation Distribution, posting, or copying of this PDF is strictly prohibited without written permission of the Transportation Research Board of the National Academy of Sciences. Unless otherwise indicated, all materials in this PDF are copyrighted by the National Academy of Sciences. Copyright © National Academy of Sciences. All rights reservedResearch Record No. 1239, Geometric Design and Operational Effects.

01414248

p. 30-40

1989

Transportation Research Record

0309049660

Figures (4) ; References (4) ; Tables (9)

Alternatives analysis; Crash rates; Equations; Four lane highways; Left turn lanes; Medians; Multilane highways; Raised separators; Regression analysis; Tables (Data); Two way left turn lanes

Six lane highways

Data and Information Technology; Design; Highways; Operations and Traffic Management; Safety and Human Factors; I20: Design and Planning of Transport Infrastructure; I73: Traffic Control; I80: Accident Studies

TRIS, TRB, ATRI

Jul 31 1990 12:00AM

• DEVELOPMENT OF HIGHWAY ALIGNMENT INFORMATION FROM PHOTOLOG DATA
• EVALUATION OF NEW PASSING ZONE GORE DESIGN
• HIGHWAY VERTICAL ALIGNMENT ANALYSIS BY DYNAMIC PROGRAMMING
• INTERACTIVE INTERSECTION DESIGN USING AN EXPERT SYSTEMS APPROACH
• INTERSECTION, DIAMOND, AND THREE-LEVEL DIAMOND GRADE SEPARATION BENEFIT-COST ANALYSIS BASED ON DELAY SAVINGS
• SAFETY EFFECTS OF LEFT-TURN LANES ON URBAN FOUR-LANE ROADWAYS