EXACT ROAD GEOMETRY OUTPUT PROGRAM FOR RETROREFLECTIVE ROAD SIGN PERFORMANCE

The angles used for the laboratory testing of retroreflective sign sheeting that are set forth in specifications are well defined and are well understood in the laboratory test setting. Not well known is exactly what values of these angular parameters, especially observation angle, occur for actual signs on the roadway. The mathematics for a complete vector structure incorporating the location data for headlamps, driver's eye, the sign, and the vehicle-to-sign (road) distance has been set up. These inputs define all locations exactly; there are no assumptions. The mathematics has been incorporated into a computer program, ERGO (Exact Road Geometry Output), which computes the exact angles at which the sign is actually seen by approaching drivers. The observation angle for actual signs is shown to be two separate values--one for each headlamp--and not simply the eye height over the headlamps. Eye setback is also shown to be a critical factor under some conditions. The ERGO data demonstrate that observation angle is a direct function of road distance: as road distance becomes less, observation angle becomes greater. Specific observation angles correspond to specific road distances. Graphs of the observation and entrance angle correlates are given for STOP and near-roadside signs, overhead guide signs, and signs at a large offset from the road edge. The effect of different size vehicles on observation angle is shown. The relationship of time to observation angle is demonstrated: as the approaching driver observes a sign at observation angles greater than 0.5 degree, these angles are traversed in fractions of a second. Both the ERGO program and its mathematical basis will be made available to others so that it can be applied to other experimental and theoretical data to better correlate laboratory test values and actual road performance of retroreflective material.

• Record URL:
  http://onlinepubs.trb.org/Onlinepubs/trr/1993/1421/1421-008.pdf
• Record URL:
  https://scholar.google.com/scholar_lookup?title=EXACT+ROAD+GEOMETRY+OUTPUT+PROGRAM+FOR+RETROREFLECTIVE+ROAD+SIGN+PERFORMANCE&author=K.+Uding&publication_year=1993
• Availability:
  • Find a library where document is available. Order URL: http://worldcat.org/isbn/0309055741
• Supplemental Notes:
  • This paper appears in Transportation Research Record No. 1421, Traffic Control Devices, Visibility, and Traffic Signal Systems. Distribution, posting, or copying of this PDF is strictly prohibited without written permission of the Transportation Research Board of the National Academy of Sciences. Unless otherwise indicated, all materials in this PDF are copyrighted by the National Academy of Sciences. Copyright © National Academy of Sciences. All rights reserved
• Authors:
  • Uding, Kenneth D
• Publication Date: 1993

Language

• English

Media Info

• Features: Figures; References; Tables;
• Pagination: p. 61-68
• Monograph Title: Traffic control devices, visibility, and traffic signal systems
• Serial:
  • Transportation Research Record
  • Issue Number: 1421
  • Publisher: Transportation Research Board
  • ISSN: 0361-1981

Subject/Index Terms

• TRT Terms: Computer programs; Distance; Offsets (Traffic signal timing); Retroreflectors; Traffic signs; Vehicle size
• Uncontrolled Terms: Observation angle
• Old TRIS Terms: Retroreflective traffic signs
• Subject Areas: Highways; Operations and Traffic Management; I73: Traffic Control;

Filing Info

• Accession Number: 00647268
• Record Type: Publication
• ISBN: 0309055741
• Files: TRIS, TRB
• Created Date: May 2 1994 12:00AM