In the 1965 Highway Capacity Manual levels of service at signalized intersections are related to load factor, which was intuitively judged the best level of service indicator available. Load factor has, however, presented such problems as its insensitivity to low service volume, absence of any rational basis for defining breakpoints, and difficulty in identifying loaded cycle. A rational method for quanifying the different levels of service at signalized intersections was therefore needed. In our research we used a road-user opinion survey that involved depicting and rating different traffic situations at a carefully selected single signalized intersection. Over 300 drivers rated randomly arranged film sequences of two types--a driver's view (microview) and an overall view (microview) of a intersection--and evaluated these films, segment by segment, in terms of appropriate levels of service. Field studies and the attitude survey provided data for the development of two psychophysical models. Statistical analysis indicated that average individual delay correlated better with level of service rating than with measured load factor and encompassed all levels of service. Of all parameters affecting levels of service, load factor was rated highest by road users. /Author/

Media Info

  • Media Type: Print
  • Features: Figures; References; Tables;
  • Pagination: pp 107-113
  • Monograph Title: Highway capacity, traffic flow, and traffic control devices
  • Serial:

Subject/Index Terms

Filing Info

  • Accession Number: 00183553
  • Record Type: Publication
  • ISBN: 0309026733
  • Files: TRIS, TRB
  • Created Date: Dec 3 1978 12:00AM