Analysis of data collected at 8 turnouts along 2-lane roads in the California mountains, showed that approximately 10 to 12 percent of all drivers with one or more followers, used any given properly designed turnout along roads, which had an annual average daily traffic of about 1,000 to 4,000 vehicles. Large trucks tended to avoid using turnouts. Turnouts on moderate grades were used by drivers with one or more followers almost as much as similar turnouts on steep grades. The most commonly observed potentially hazardous maneuvers involved cutting-back-in before the entire platoon has passed. Few turnout users actually stop; average speeds of 26 and 31 mph were observed at 2 of the longer turnouts. The turnouts with total lengths of 200 to 250 feet appear suitable for low speed roads, and 400 to 450 feet appear suitable for high speed roads. Optimal lengths of turnouts are not necessarily the same as optimal lengths for chain control locations, and paved widths of 9 to 12 feet are adequate along cut slopes. Adequate sight distance is necessary so that low speed vehicles leaving the turnouts could be spotted. Comments are made on the standard signs, pavement markings and operations at turnouts in California. The study concludes that turnouts are safe and can provide considerable benefits, but are not a substitute for a passing lane of adequate length.

  • Corporate Authors:

    California Department of Transportation

    1120 N Street
    Sacramento, CA  United States  95814
  • Authors:
    • ROONEY, F
  • Publication Date: 1976-11

Media Info

  • Features: Figures; Photos; Tables;
  • Pagination: 63 p.

Subject/Index Terms

Filing Info

  • Accession Number: 00147730
  • Record Type: Publication
  • Report/Paper Numbers: Eval. Rpt.
  • Created Date: Feb 16 1977 12:00AM