GUARDRAIL ENCROACHMENT MONITOR - GEM. SUMMARY REPORT

An experimental instrumentation system for monitoring long lengths of traffic railings to detect encroaching vehicles and measuring impact conditions has been developed and subjected to preliminary evaluation. The system makes use of the traffic railing as part of a transmission line carrying two radiofrequency waves. The radiofrequency energy reflected from vehicles entering the electromagnetic field about the line is detected and used to determine vehicular speed, direction, angle, location, path and size. A solid-state, digital data acquisition system is triggered by a detected encroachment to record pertinent data. Capability to record data on up to 50 encroachments is available. Computer data processing generates plots of vehicle path and tabulates data on time, speed, angle, location of encroachment, vehicle size and nature of encroachment. The system is packaged to be suited for unattended roadside installation and will operate continuously from a self-contained 12 V battery for periods of up to 10 days without servicing. Tests indicate generally satisfactory performance, speed measurement accuracy of plus or minus 0.5 mph (plus or minus 0.8 km/hr), angle measurement accuracy of plus or minus 1 deg, location accuracy of plus or minus 10 ft (plus or minus 3m), parallel range of more than 1300 ft (396m), and perpendicular range of 3 ft (lm) or more. Long term evaluation in a roadside installation is needed to further establish the reliability and limitations. (FHWA)

• Corporate Authors:

  Southwest Research Institute

  6220 Culebra Road, P.O. Drawer 28510
  San Antonio, TX  United States  78228-0510

  Federal Highway Administration

  Engineering Research and Development Bureau, 1200 New Jersey Avenue, SE
  Washington, DC  United States  20590
• Authors:
  • King, J D
  • CERWIN, S A
• Publication Date: 1981-5

Media Info

• Pagination: 45 p.

Subject/Index Terms

• TRT Terms: Data collection; Electromagnetic waves; Guardrails; Information processing; Instrumentation; Measurement; Monitoring; Motor vehicles; Radio waves; Speed; Traffic speed; Vehicle detectors
• Old TRIS Terms: Data recording
• Subject Areas: Highways; Operations and Traffic Management; I71: Traffic Theory;

Filing Info

• Accession Number: 00341305
• Record Type: Publication
• Report/Paper Numbers: FHWA-RD-80-174, 15-4017, FCP 31H3-142
• Contract Numbers: DOT-FH-11-8498
• Files: TRIS, USDOT
• Created Date: Dec 22 1981 12:00AM