In 1976, the Local Transportation and Roads Directorate of the Department of Transport organised a survey of journey speeds and flows on all main roads in the principal cities of five conurbations outside London (population range 300000 to 1100000) and in eight towns (population range 80000 to 560000). The study was similar to those undertaken in 1963 (eight towns only), 1967 and 1971 to monitor long term trends in urban traffic characteristics. TRRL undertook the analysis of the survey results and this report outlines the survey techniques used, and presents summaries of measurements made during the weekday daytime off-peak and peak periods. In 1976 the overall mean flow in the conurbation towns was 1360 PCU/h in the off-peak, rising to 1915 PCU/h in the peak. The flows were about 15 per cent higher than those observed during the same periods in the eight towns (1165 PCU/h and 1635 PCU/h respectively). Speeds in the conurbation towns as a whole (38.0 km/h, off-peak, and 33.7 km/h, peak) were on average 4 km/h higher than the corresponding eight towns' speeds. In the central areas, off-peak and peak traffic flows in the two groups were similar (about 1380 PCU/h and 1735 PCU/h respectively), as was the mean peak speed of around 20.6 km/h. The eight towns' average off-peak speed (25 km/h) was about 4 km/h higher than the conurbation value. Since the surveys began there has been very little growth in overall traffic flows, but a dramatic reduction has occurred in street parking, particularly during off-peak periods in the central areas, where the parking density is now on average only about one third of what it was in 1967. Average speeds have shown a slow but steady increase, no doubt related to the reduction in parking and to other traffic management schemes. (Author/publisher)
Samenvatting