The paper describes the conceptual background and latest results of an ongoing investigation into the characteristics of environmental capacities of urban arterial streets for traffic management purposes. In the study reported in this paper, environmental impacts are limited to air pollution and the focus is on the situations around the major intersections. Using available data on the physical, control and traffic demand conditions together with emission characteristics of vehicles, a simulation study of the traffic operations around three major intersections in the city of Nairobi, Kenya was carried out. The traffic performance characteristics of the facilities and the concentrations of major air pollutants of 15m and 40m from the roadside were determined. The results were then used to derive the maximum traffic volumes of different air quality standards. Finally, the effects of some possible changes in the control and demand conditions on the magnitudes of the capacities were determined and analyzed. The results show that under the current conditions, the concentrations of lead (pb) and hydrocarbon (HC) are 30 to 40 times the WHO standards and that the environmental capacities are much less than the conventional traffic capacities at all the locations. In addition, changes in signal settings and other supply management measures did not result in significant improvements in the environmental capacities. One main implication of the results of the study is that environmental capacity of an urban arterial street appears to be its critical load. Thus, it is proposed that the value of volume to environmental capacity ratio should be used to define level of service criteria for planning urban street improvement schemes to enhance better quality of life in the cities. For the covering abstract see IRRD 877018.


  • English

Media Info

  • Features: References;
  • Pagination: p. 23-37

Subject/Index Terms

Filing Info

  • Accession Number: 00722309
  • Record Type: Publication
  • Source Agency: Transport Research Laboratory
  • ISBN: 0-86050-282-1
  • Files: ITRD
  • Created Date: Jun 28 1996 12:00AM