Research Papers

Assessing speed consistency of horizontal geometric design using a microscopic simulation approach

Filename Duong.pdf
Filesize 291 KB
Version 1
Date added June 6, 2010
Downloaded 1 time/fois
Category 2010 CMRSC XX Niagara
Tags Session 1A
Author/Auteur David Duong, Michael Mandelzys, Frank Saccomanno, Bruce Hellinga


Highway geometric design has significant impacts on roadway safety. This is especially true, for tangent-curve segments of highways where speed consistency between adjacent road sections is directly correlated with accident risk. Two speed consistency measures found in the literature are delta-V85 and 85MSR. For a tangent-curve section of highway, the delta-V85 is expressed as the difference in the 85th percentile speed between a point on the tangent 200 meters upstream of the beginning of the curve and the midpoint of the curve segment. The 85MSR measure is calculated from observed speed changes for each individual vehicle between the tangent and the curve section of they highway, and represents the 85th percentile of these speed changes. The 85MSR is regarded as a more accurate measure of speed consistency since it looks at speed changes in individual vehicles; the delta-V85 is known to underestimate the true amount of speed changes experienced by vehicles. Although 85MSR provides a more accurate measure of speed consistency, it requires the gathering of individual vehicle speed data along both the tangent and curve segments, which is difficult and costly to obtain. A recent FHWA report entitled “Surrogate safety measures from traffic simulation models” has stated that simulation platforms when properly calibrated can provide accurate and reliable safety performance outputs. This study proposes the use of microscopic simulation to predict the 85MSR and delta-V85 (speed consistency) measures for tangent-curve freeway segments. The simulated results are compared to field data to determine whether simulation is a viable alternative to field data.

David Duong, Michael Mandelzys, Frank Saccomanno, Bruce Hellinga