EXPERIMENTAL MEASUREMENTS OF PERCEPTUAL THRESHOLDS IN CAR-FOLLOWING

A SERIES OF EXPERIMENTS WAS CARRIED OUT TO MEASURE PERCEPTUAL THRESHOLDS OF DRIVERS IN CAR-FOLLOWING. EARLY RESULTS FROM PILOT EXPERIMENTS REVEALED 2 BASIC DIFFICULTIES ASSOCIATED WITH PREVIOUS ATTEMPTS REPORTED IN THE LITERATURE TO MEASURE RELATIVE MOTION THRESHOLDS IN CAR- FOLLOWING: FIRST, IT WAS SOMETIMES POSSIBLE FOR THE SUBJECT TO PERCEIVE THE PITCHING OF THE LEAD CAR IN RESPONSE TO THE INITIATION OF AN ACCELERATION OR DECELERATION MANEUVER AND THEREBY INFER IMMEDIATELY THAT A CHANGE HAD OCCURRED. SECOND, PERMITTING THE SUBJECTS TO RESPOND WHEN THEY WERE SUFFICIENTLY CONFIDENT THAT THEY HAD DETECTED A CHANGE INTRODUCED AN UNMEASURABLE VARIABLE. THIS UNMEASURABLE VARIABLE ARISES BECAUSE A SUBJECT WISHING TO MAKE NO ERRORS MIGHT WAIT FOR LARGER STIMULI THAN ONE WISHING TO REGISTER QUICK RESPONSES, EVEN THOUGH BOTH MIGHT HAVE THE SAME SENSITIVITY. AN EXPERIMENT WAS DESIGNED TO CIRCUMVENT THESE DIFFICULTIES. BY MEANS OF AN OCCLUSION DEVICE, SUBJECTS SEATED AS PASSENGERS IN A FOLLWOING CAR TRAVELING AT 45 MPH WERE GIVEN CONTROLLED LOOKS, NORMALLY OF 4-SEC DURATION, AT A LEAD CAR MOVING AT A CONSTANT SPEED. FOR EACH EXPOSURE THE SUBJECTS INDICATED WHETHER THEY PERCEIVED NEGATIVE (THAT IS, THE CARS CAME CLOSER) OR POSITIVE RELATIVE MOTION. THE RESULTS INDICATE THAT (A) THE DOMINANT CUE USED TO JUDGE THE SIGN OF RELATIVE MOTION IS THE AVERAGE VALUE OF RELATIVE SPEED DIVIDED BY SPACING; (B) THERE IS RESPONSE BIAS IN FAVOR OF INDICATING NEGATIVE RATHER THAN POSTIVE RELATIVE MOTION; AND (C) THERE IS A HIGH LEVEL OF SENSITIVITY TO RELATIVE MOTION. FOR EXAMPLE, IF A LEAD CAR WERE CLOSING ON A FOLLOWING CAR AT 3 MPH, THE FOLLOWING DRIVER'S PROBABILITY OF CORRECTLY IDENTIFYING THE SIGN OF RELATIVE MOTION AS NEGATIVE RATHER THAN POSITIVE AFTER A 4-SEC OBSERVATION IS 0.99 WHEN THE SPACING IS 200 FT. /AUTHOR/

• Record URL:
  http://onlinepubs.trb.org/Onlinepubs/hrr/1973/464/464-002.pdf
• Availability:
  • Find a library where document is available. Order URL: http://worldcat.org/isbn/0309021979
• Supplemental Notes:
  • Publication of this paper sponsored by Committee on Road User Characteristics. 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:
  • Evans, Leonard
  • Rothery, Richard
• Discussers:
  • Mortimer, Rudolf G
  • Snider, John N
• Conference:
  • 52nd Annual Meeting of the Highway Research Board
  • Location: Washington District of Columbia, United States
  • Date: 1973-1-22 to 1973-1-26
• Publication Date: 1973

Media Info

• Media Type: Print
• Features: Figures; References; Tables;
• Pagination: pp 13-29
• Monograph Title: Driver behavior: research methods
• Serial:
  • Highway Research Record
  • Issue Number: 464
  • Publisher: Highway Research Board

Subject/Index Terms

• TRT Terms: Behavior; Distance perception; Drivers; Experiments; Headways; Perception; Reaction time
• Uncontrolled Terms: Driver reaction
• Old TRIS Terms: Perception distance; Thresholds (Perception)
• Subject Areas: Highways; Safety and Human Factors;

Filing Info

• Accession Number: 00224524
• Record Type: Publication
• ISBN: 0309021979
• Files: TRIS, TRB
• Created Date: Apr 20 1974 12:00AM