An Evaluation of the Following Too Closely Monitor System on a Four-lane Undivided Highway: Interim Report

Report No: 76-R51

Published in 1976

About the report:

The FOLLOWING TOO CLOSELY (FTC) MONITOR system is an experimental device designed to measure vehicle gaps at a point along the highway and to advise the motorist, by means of a flashing message on a sign, that he is following the car in front of him too closely. On October 31, 1974, ten FTC monitors were installed at four sites on a 6-mile 4-lane undivided section of Route 1 in Woodbridge, Virginia. As the FTC system is a new concept in highway safety, an investigation was conducted to evaluate the effects of the system on vehicle spacings, speeds, and accidents. Traffic and accident data were collected for a period 1 year before and 1 year after the monitors were installed. The results of the study reveal that use of the FTC system resulted in a significant reduction in accidents. A decrease in injury, property damage, and all crash types, including rear end collisions, was found. Monitors located in a suburban area, within a 0.5-mile section downstream from traffic signals, were found to be more effective in reducing incidences of following too closely and accidents than were monitors in rural areas. After 9 months of operation, the monitors appeared to begin to lose their effectiveness in decreasing the number of short vehicle gaps and reducing accidents. A minimal police effort was used to issue citations to motorists who were following at unsafe intervals. The enforcement campaign was effective in decreasing the number of short vehicle gaps and reducing accidents. The monitors were found to be cost effective. Further research is recommended to determine the amount of police enforcement necessary to sustain long-term benefits of the system.

Disclaimer Statement:The contents of this report reflect the views of the author(s), who is responsible for the facts and the accuracy of the data presented herein. The contents do not necessarily reflect the official views or policies of the Virginia Department of Transportation, the Commonwealth Transportation Board, or the Federal Highway Administration. This report does not constitute a standard, specification, or regulation. Any inclusion of manufacturer names, trade names, or trademarks is for identification purposes only and is not to be considered an endorsement.


Other Authors

Martin R. Parker

Last updated: January 29, 2024

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