Impact of Individual Side Friction Factors on Free-Flow Speed: Case Study on Urban Road Links in Dar-es-Salaam, Tanzania

Operating speed is an important measure of performance on urban roads. There are many factors that affect operating speed; among them are the so-called ‘side friction factors’. These are defined as all those events along the road which have an impact on traffic performance measures. They are normally very frequent in densely populated areas in developing countries while they are random and sparse in developed countries bringing about less interest for research. In this paper, research was conducted to study the impact of four friction factors that were identified to be frequent on Dar-es-salaam roads. They included Pedestrians (PED), Bicycles (BIC), Non-Motorized Vehicles (NMV), and Parking-Stopping Vehicles (PSV). An empirical study was designed where two methods based on “average free-flow speed” and “free-flow spot-speed” were devised and applied for data collection and analysis. Data were collected in October 2005 on six urban major arterial road-links of two types; two-lane two-way and four-lane two-way roads. Traffic flow, traffic composition, speed, and side friction data were collected by extensive use of video recording and retrieved by application of a “semi-automatic video analyzer” (SAVA) computer program specially designed for traffic studies, whereas the analysis was carried out by application of statistical methods. The results showed that all the four factors exhibited significant impact on the speed of two-lane two-way roads, while only one factor (PSV) was significant on four-lane two-way roads. It was concluded that knowledge of side friction exposure is important for designing and planning purposes in places with high friction levels.


  • English

Media Info

  • Media Type: CD-ROM
  • Features: Figures; References; Tables;
  • Pagination: 15p
  • Monograph Title: TRB 86th Annual Meeting Compendium of Papers CD-ROM

Subject/Index Terms

Filing Info

  • Accession Number: 01055882
  • Record Type: Publication
  • Report/Paper Numbers: 07-1210
  • Files: BTRIS, TRIS, TRB
  • Created Date: Feb 8 2007 5:49PM