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Title:

Analysis of 2+1 Roadway Design Alternatives

Accession Number:

01004394

Record Type:

Component

Availability:

Transportation Research Board Business Office

500 Fifth Street, NW
Washington, DC 20001 United States

Abstract:

One of the main problems encountered when analyzing 2+1 design is to determine the optimum length and frequency of additional lanes. NCHRP recommends that passing lane lengths on 2+1 roadways should be consistent with optimal lengths for isolated passing lanes on two-lane highways. However, it is not reported that any special analysis was carried out in this aspect. Then, it was decided to analyze different layouts of 2+1 design using Twopas simulation model. The model was previously calibrated for traffic conditions on Polish roads. The analysis was done for an 8.4 km long section with fixed-length additional lanes located continuously in alternating directions. The analyzed alternative module lengths were: 600, 950, 1300 and 2000 m. Two measures of effectiveness were analyzed: percent time spent following (PTSF) and total vehicle-hours. Two-lane two-way section with passing allowed throughout the whole length was assumed as the base-case. The parameters of the analysis were: traffic volume and percent of trucks. As a result of the analysis the relationships between traffic volume and PTSF and time savings were derived. The relationships show that for any module length from 950 to 2000 m there is no significant difference in the measures of effectiveness for the whole range of traffic volumes analyzed (from 250 to 1500 veh/h/dir), whereas for the 600 m module the calculated values are slightly worse. Thus, in practice any module length from the range of 1000-2000 m can be used, regardless of traffic volume. These results are different from the ones presented by NCHRP.

Monograph Accession #:

01004374

Language:

English

Corporate Authors:

Transportation Research Board

500 Fifth Street, NW
Washington, DC 20001 United States

Authors:

Szagala, Piotr

Pagination:

15p

Publication Date:

2005

Conference:

3rd International Symposium on Highway Geometric Design

Location: Chicago Illinois, United States
Date: 2005-6-29 to 2005-7-1
Sponsors: Transportation Research Board; American Association of State Highway and Transportation Officials (AASHTO); Federal Highway Administration; American Society of Civil Engineers; Association Mondiale de la Route; International Road Federation; Institute of Transportation Engineers (ITE); National Association of County Engineers; Transportation Association of Canada (TAC); Chicago Department of Transportation; Illinois Department of Transportation; Illinois State Toll Highway Authority

Media Type:

CD-ROM

Features:

Figures (6) ; References (4) ; Tables (3)

Geographic Terms:

Poland

Subject Areas:

Design; Highways; I20: Design and Planning of Transport Infrastructure

Files:

TRIS, TRB, ATRI

Created Date:

Sep 21 2005 2:40PM