AN ASSESSMENT OF THE EFFECTIVENESS OF THE FOLLOWING-TOO- CLOSELY MONITOR

The purpose of this study was to evaluate the effectiveness of the Following-Too-Closely Monitor (FTC), a five by eight foot traffic sign and logic system that calculates vehicular time gap (the time it takes the front of a following vehicle to reach a point on the roadway that the rear of the leading vehicle has just passed) and presents a massage to the following motorist if the time gap is improper. A "violation" message is flashed if the time gap is 0.70 seconds or less, and a "danger" message is presented if the time gap is between 0.70 seconds and 1.25 seconds. The FTC system used in this study was installed in Raleigh, North Carolina, on South Wilmington Street, an urban, four-lane divided roadway carrying approximately 30,000 vehicles per day. Two FTC signs were installed at a single southbound location (one for each lane), while the northbound lanes served as a control. The rear-end accident data for South Wilmington Street fluctuate so widely over the four year study period that it is not possible to definitely quantify the FTC effort. For the southbound direction, a straight line projection indicated that the number of rear-end crashes occurring in the year after FTC installation were precisely what would have been expected had there been no signs installed. However, a straight line projection developed for the ratio of the southbound rear-end accidents to the control street rear-end accidents indicated a 28 percent reduction in the observed ratio when compared to the expected ratio. In terms of the time gap data, a reduction in the percentage of "violation" and "danger" occurrences was observed in the southbound lanes after the FTC was installed. The largest reduction occurred at the station located immediately downstream from the sign location with smaller decreases at two stations farther downstream which were located beyond a signalized intersection.

• Supplemental Notes:
  • Prepared for the North Carolina Department of Transportation in cooperation with the FHWA, DOT.
• Corporate Authors:

  University of North Carolina, Chapel Hill

  Highway Safety Research Center
  Chapel Hill, NC  United States  27599
• Authors:
  • Hunter, W H
  • Bundy, H L
  • Daniel, R B
• Publication Date: 1976-6

Media Info

• Features: Appendices; Figures; References; Tables;
• Pagination: 93 p.

Subject/Index Terms

• TRT Terms: Following distance; Gap acceptance; Measures of effectiveness; Rear end crashes; Traffic signal control systems; Variable message signs
• Uncontrolled Terms: Effectiveness
• Old TRIS Terms: Following distance (Of vehicles)
• Subject Areas: Highways; Operations and Traffic Management;

Filing Info

• Accession Number: 00142576
• Record Type: Publication
• Files: TRIS
• Created Date: Jan 16 1977 12:00AM