Occupancies and flows were jointly sampled from numerous freeway segments in nearly stationary, unqueued traffic. The data from one segment were typically averaged across all lanes there and plotted. Each plot was compared with one sampled at a neighboring freeway segment, with the two segments differing only in their number of travel lanes. Such comparisons were repeated for a total of five pairs of segments on five freeways in and near Toronto, Canada and in California. All occupancy-flow relations were piece-wise linear in form for average flows up to about 2,000 vehicles per hour per lane. Only when traffic became moderately dense did average vehicle speeds diminish with increasing occupancies. The occupancy above which these speed diminutions occurred was the same for both segments in a pair. Notable, however, the average vehicle speed corresponding to a given occupancy was always higher on the segment with the larger number of lanes. The driver psychology that can explain some of these findings is discussed. Findings are also contrasted with information currently provided in traffic handbooks.

This paper focuses on the estimation of highway maintenance marginal costs. Highway maintenance marginal cost has been estimated in the literature using the perpetual overlay indirect approach. This approach assumes that pavement overlay costs dominate maintenance costs and ignores other maintenance activities. This paper focuses on two questions. First, is it acceptable to ignore the less costly activities? Second, if multiple maintenance activities are to be considered, is it acceptable to ignore their interdependence? The results show that less costly maintenance activities cannot be ignored. Furthermore, if multiple activities are to be considered, their interdependence should be taken into account.

A bottleneck with a diminished capacity is shown to have arisen on a freeway segment whenever queues from the segment's off-ramped spilled over and occupied its mandatory exit lane. It is also shown that longer exit queues from the over-saturate off-ramp were accompanied by lower discharge rates for non-exiting vehicles. The explanation appears to be rubber-necking on the part of the non-exiting drivers. Whenever the of-ramp queues were prevented from spilling over to the exit lane (by changing the logic of a nearby traffic signal), much higher flows were sustained on the freeway segment and a bottleneck did not arise there. These observations underscore the value of control strategies that enable diverging vehicles to exit a freeway unimpeded. Key words: Freeway Traffic Control, Off-Ramps, Bottlenecks