HIGHWAY FOG

RESEARCH WAS CONDUCTED TO : (1) REVIEW AND REPORT ON PAST AND CURRENT RESEARCH OF WARM AND COLD FOG AS IT AFFECTS HIGHWAY OPERATION, INCLUDING SUCH FACTORS AS FOG ABATEMENT GUIDANCE SYSTEMS, MEASURES OF VISIBILITY, AND EFFECT ON TRAFFIC OPERATIONS, (2) DETERMINE THE EFFECTS OF DAY AND NIGHT FOG LEVELS ON DRIVER PERFORMANCE AND TRAFFIC OPERATIONS, (3) EXPLORE THE FEASIBILITY OF WARM AND COLD FOG ABATEMENT AND OF VEHICULAR GUIDANCE SYSTEMS UNDER HIGHWAY CONDITIONS, (4) TEST FOG ABATEMENT METHODS AND GUIDANCE SYSTEMS UNDER HIGHWAY CONDITIONS, AND (5) SUGGEST WAYS AND MEANS OF OBTAINING MAX. EFFECTIVENESS OF SYSTEMS TO COMBAT REDUCED VISIBILITY DUE TO FOG. HIGHWAY SAFETY IMPROVEMENT IN ENVIRONMENTS WHERE FOG IS ENCOUNTERED IS DESIRED. A REVIEW OF THE LITERATURE INDICATED THAT FOG HAS THE FOLLOWING EFFECTS: (1) A SLIGHT REDUCTION IN ACCIDENT FREQUENCY, (2) AN INCREASE IN THE LIKELIHOOD THAT AN ACCIDENT WILL RESULT IN A FATALITY, AND (3) AN INCREASE IN THE LIKELIHOOD THAT ACCIDENTS WILL INVOLVE EITHER A SINGLE VEHICLE OR MORE THAN THREE VEHICLES. TRAFFIC MEASUREMENTS MADE DURING THIS PROJECT INDICATE THAT: (1) SPEEDS WERE SLIGHTLY LOWER IN FOG, (2) THE PROBABILITY OF OVERDRIVING ONES VISUAL RANGE WAS GREATLY INCREASED, AND (3) LATERAL LOCATION AND VEHICLE INTERACTIONS WERE NOT AFFECTED BY FOG. IT IS CONCLUDED THAT DRIVERS EXERCISE MORE CAUTION IN FOG, BUT THAT THE INCREASE IN OVERDRIVING PROBABLY EXPLAINS THE INCREASED SEVERITY OF ACCIDENTS. FIELD TESTS DEMONSTRATED THAT VISIBILITY IN DENSE FOG CAN BE IMPROVED BY SEEDING WITH PRACTICAL AMOUNTS OF CAREFULLY SIZED HYGROSCOPIC MATERIAL. OTHER CONCEPTS (VEGETATION BARRIERS TO INFLUENCE THE MOVEMENT OF SHALLOW FOG, MONOLAYER TO INHIBIT EVAPORATION FROM WATER RESERVOIRS, USE OF HELICOPTERS TO MIX DRIER AIR WITH FOG) HAVE LIMITED APPLICATION AND MAY BE TAILORED TO SPECIFIC TYPES OF HIGHWAY FOG. PREVIOUSLY SUGGESTED VEHICLE GUIDANCE PROCEDURES WERE STUDIED. SPECIALLY DESIGNED LIGHTS MOUNTED NEAR THE ROAD SURFACE, PRODUCING AN AREA OF ILLUMINATION DIRECTLY ABOUT 110 DEGREES TO THE DIRECTION OF TRAFFIC FLOW CAN BE USED EFFECTIVELY TO PROVIDE ILLUMINATION FOR NIGHT DRIVING IN FOG. A VEHICLE GUIDANCE SYSTEM INVOLVING THE USE OF POLARIZED HEADLAMPS WAS EVALUATED IN FIELD EXPERIMENTS AND JUDGED IMPRACTICAL AS AN AID TO DRIVERS IN FOG. MEASUREMENTS OF THE EFFECT OF VEHICLE LIGHTING ON VISIBILITY SHOW THAT REAR LIGHTING SYSTEMS CAN BE IMPROVED TO ALLOW BETTER DETECTION OF VEHICLES IN FOG.

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    • 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. Nchrp PROJECT 5-6 48 PP, 4 FIG, 3 TAB, 18 REF, 8 APP
  • Publication Date: 1970

Media Info

  • Media Type: Digital/other
  • Serial:
    • NCHRP Report
    • Issue Number: 95
    • Publisher: Transportation Research Board
    • ISSN: 0077-5614
  • Publication flags:

    Open Access (libre)

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Filing Info

  • Accession Number: 00225835
  • Record Type: Publication
  • Files: TRIS, ATRI
  • Created Date: Oct 13 1970 12:00AM