Results of the scientific investigation accompanying the pilot trial of 30 kph limit in side streets and 50 kph limit in priority streets.

Following the success of pilot 30kph limit zones in the city of Graz, Austria, a city-wide 30kph scheme was adopted with the exception of 50kph `priority' roads. This paper describes a study of the traffic situation before and after the implementation of the scheme. Aspects considered include a) road accidents, b) average speed, c) driver behaviour, d) changes to mode of transport, e) exhaust emissions and fuel consumption, f) traffic noise and g) public attitudes to the scheme. The speed limit was found to improve safety, reduce noise pollution but make little difference to emissions.