Parking controls have been used for many years as a means of influencing travel demand and managing traffic. However, little is known about the changes in parking activity associated with different parking controls and the resulting effects on vehicle emissions and ambient air pollution. This report describes an evaluation of parking duration and vehicle exhaust emissions using the remote sensing technique. Remote sensing surveys were conducted at three car parks which covered a broad range of parking duration, and at each site the volumetric concentrations of carbon monoxide (CO) and hydrocarbons (HC) in the exhaust plume of vehicles entering and leaving were measured using the system. Functions relating the %CO and %HC values at the exit of a car park to parking duration were obtained, and a procedure was developed for deriving corresponding mass-based emisson functions. The relationships indicate that the CO and HC exit mass emissions per vehicle following long parking durations (9 hours) are around three times higher than exit mass emissions following short parking durations (1 hour). A simple theoretical example is provided to show how the relationships between fleet mass emissions and parking duration could be used to evaluate the impacts of parking controls. The example involves the evaluation of the effects of changes in parking duration at an off-street car park. The results indicate that, for parking durations shorter than around four hours, changes in vehicle turnover are a more important determinant of total daily emissions of CO and HC than changes in emission levels per vehicle. In such situations it is likely that substantial changes in daily emissions would occur if the average parking duration at a car park changed. Any changes in parking control that result in the average parking duration remaining longer than four hours would have comparatively little impact on total daily emissions. (A)

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