Prepared by:

Alireza Hadayeghi, M.A.Sc, Ph.D. (Candidate) Manager, Transportation Safety Systems, Synectics Transportation Consultants Inc.

Brian Malone, P.Eng., PTOE, President Synectics Transportation Consultants

Scott McIntyre, Dipl. T., Dipl. F. Transportation Safety Technologist, Synectics Transportation Consultants

Abstract

The objective of this study was to measure the effectiveness of a coloured slurry seal traffic calming treatment, used to “narrow” lanes of a road, in reducing driving speeds and traffic volume on residential streets. A before-and-after study with a comparison group was used to measure the effect of the treatment on the average 85th percentile and average traffic volume for the treated street. The before-and-after study did not naively consider changes on the treated road but also examined changes that may be taking place in the overall behaviour of traffic. Traffic data for this study was collected from the treatment and control sites prior the traffic measure being installed and then collected one month following the treatment and four months following the completion of the treatment installation.

The results of analyzing the average 85th percentile speeds indicate a reduction in vehicle speeds from before to one month and four months after periods. However, the results were found not be statistically significant at a 5 percent confidence level. The results of the study on traffic volume were mixed. The 24 hour average traffic volume one month after implementation of the traffic calming showed a statistically significant increase. It is speculated that a possible reason for this increase might be the novelty effect of the new traffic calming treatment measure, attracting drivers to the treated site to view the treatment. However, four months after application of the slurry was introduced the average 24 hour traffic volume showed a statistically significant decrease from the before period.

For a complete copy of this paper, please contact: jsuggett@synectics-inc.net