VERTICAL ALIGNMENT EFFECTS ON SAFE VEHICLE OPERATION

THE VERTICAL ALIGNMENT DESIGN CRITERIA USED ON MODERN HIGHWAYS HAS EVOLVED FROM THE STANDARDS OF THE PAST. EMPHASIS PLACED ON IMPROVING THE ROADWAY CROSS SECTION HAS NEGLECTED THE VERTICAL ALIGNMENT, RESULTING IN A ROADWAY WITH A 70-MPH HORIZONTAL ALIGNMENT AND A 50-MPH VERTICAL ALIGNMENT. MODERN OPERATING SPEEDS COMBINED WITH HIGHER SAFETY STANDARDS REQUIRE CONSIDERATION OF A NEW APPROACH TO THE ESTABLISHMENT OF VERTICAL DESIGN CRITERIA. EXAMPLES ARE PRESENTED ILLUSTRATING THE NEED FOR A DESIGN CONCEPT WHICH PROVIDES THE DRIVER VISUAL CONTACT WITH THE ROADWAY SURFACE GREATER THAN IS CURRENTLY BEING PROVIDED. THE IMPORTANCE IS EMPHASIZED OF DRIVER EXPECTANCY IN SAFE MOTOR VEHICLE OPERATIONS. WHEN THE PHYSICAL SITUATION DIFFERS FROM THE EXPECTED SITUATION, A VERY COMPLEX DECISION-MAKING PROCESS IS INVOLVED REQUIRING THAT: (1) THE INFORMATION AVAILABLE TO THE DRIVER MUST BE SUFFICIENT TO CONVINCE HIM THAT HIS EXPECTED SITUATION IS INDEED INCORRECT, (2) THE INCORRECT SET OF EXPECTATIONS MUST BE REPLACED WITH A NEW SET, AND (3) THE USUAL PERCEPTION-REACTION PROCESS IS CARRIED OUT TO ARRIVE AT AN APPROPRIATE COURSE OF ACTION. A NEW CONCEPTUAL FORMAT FOR VERTICAL ALIGNMENT WHICH SHOULD MORE NEARLY MEET THE NEEDS OF THE DRIVER CAN BE DEVELOPED BASED ON RESULTS PRESENTED IN A TABLE ON MINIMUM RESPONSE DISTANCES FOR UNEXPECTED SITUATIONS. THE DESIRABLE DESIGN CRITERIA ARE ALSO PRESENTED IN A TABLE. WHEN SIGHT DISTANCES TO THE PAVEMENT SURFACE CANNOT BE PROVIDED FOR, CARE SHOULD BE EXERCIZED TO INSURE THERE IS A MINIMUM PROBABILITY OF OBJECTS, PEDESTRIANS, ANIMALS, OR SLOW-MOVING VEHICLES IN THAT AREA.

• Availability:
  • Find a library where document is available. Order URL: http://worldcat.org/oclc/1587330
• Supplemental Notes:
  • pp 3-4, 3 TAB, 3 REF
• Authors:
  • Woods, D L
• Publication Date: 1970-4

Media Info

• Serial:
  • Texas Transportation Researcher
  • Publisher: Texas Transportation Institute
  • ISSN: 0040-4748

Subject/Index Terms

• TRT Terms: Alignment; Curves (Geometry); Decision making; Design; Drivers; Highway design; Information dissemination; Perception; Reaction time; Sight distance; Vehicle safety
• Uncontrolled Terms: Design criteria; Driver reaction; Vertical curvature
• Old TRIS Terms: Vehicular safety
• Subject Areas: Data and Information Technology; Design; Highways; Operations and Traffic Management; Safety and Human Factors;

Filing Info

• Accession Number: 00225769
• Record Type: Publication
• Files: TRIS
• Created Date: Jul 27 1970 12:00AM