Influence of Various Restrictions on Speed-Flow Models

The paper presents traffic speed models developed on the basis of numerous measurements. In studies of the speed–flow relationships the following research issues were analyzed: impacts of the speed limit, traffic flow, traffic flow composition, and time of day on speed flow; and impacts of qualitative road and roadside features on free-flow speed (cross sections, road function, accessibility, intensity of development, and roadside pedestrian traffic). The research included road sections with numerous constraints of traffic freedom. Such sections comprise sections of roads through built-up areas (small communities and towns). The regression analyses, with use of generalized multiple regression, was the basic tool in investigations. Additionally, in analyzing data from speed measurements, the classic form of the logit function for a multiple-valued regression was applied. The analyses showed that even at general and posted speed limits the characteristic traffic flow–speed relations can be identified. The shape of these relations is characteristic for empirical results in which spread of recorded values is typical for randomness and impacts of local factors. Average speed in traffic flow depends not only on geometrical alignment of a road cross section but also on local factors as well as speed limits. Speed in free-flow traffic is significantly influenced by qualitative road and roadside characteristics. Most important of these factors are: type of cross section, intensity of roadside development, and accessibility of the road.

• Record URL:
  • http://www.trb.org/Publications/Blurbs/165625.aspx
• 
• Availability:
  • Find a library where document is available. Order URL: http://worldcat.org/issn/00978515
• Authors:
  • Tracz, Marian
  • Gaca, Stanislaw
• Conference:
  • Greenshields 75 Symposium
  • Location: Woods Hole MA, United States
  • Date: 2008-7-8 to 2008-7-10
• Publication Date: 2011-6

Language

• English

Media Info

• Media Type: Web
• Pagination: p 85
• Monograph Title: 75 Years of the Fundamental Diagram for Traffic Flow Theory: Greenshields Symposium
• Serial:
  • Transportation Research Circular
  • Issue Number: E-C149
  • Publisher: Transportation Research Board
  • ISSN: 0097-8515

Subject/Index Terms

• TRT Terms: Accessibility; Alignment; Flow speed relationships; Free flow speeds; Logits; Multiple regression analysis; Real estate development; Speed limits; Traffic flow; Traffic flow theory; Traffic models
• Subject Areas: Highways; Operations and Traffic Management; I71: Traffic Theory;

Filing Info

• Accession Number: 01349733
• Record Type: Publication
• Files: TRIS, TRB
• Created Date: Aug 15 2011 11:04AM