Abstract
Traffic speeds and flows were observed at nine road tunnels at different times between October 1972 and August 1976 to obtain speed/flow relationships. At two sites, speeds were also observed on sections outside the tunnels for comparison with speeds inside the tunnels. The measured speed flow values for the tunnels generally fall within the range of speeds and flows observed on suburban main roads and were somewhat lower than those found on rural main roads. From the limited evidence at two sites, short, straight, well-illuminated tunnels do not markedly affect traffic speeds. (Author/publisher)