Car Travel Time Variability on Links of a Radial Route in London: Results

This working paper describes the results of a study of the variability of travel times and its causes on links of a secti.on of the A41 radial route in north London in the spring and summer of 1987. The objectives were to estimate the extent of variability of travel times of private car users and to explain the observed variability by means of models incorporating a range of traffic factors, including traffic flow, and incorporating seasonal differences. In general the spring was slower and showed more travel time variation between time periods than the summer. slower and more variable links in the spring tended to behave similarly in the summer. The models produced explained around two thirds of the travel time variation between periods, but the explanatory power and explanatory variables differed between links. Blocking of the downstream exit from links was the single variable which was significant in affecting traffic times on most links.