Change of Acoustic Climate Following Introduction of Road Narrowing on Divided Street

Abstract

Challenges involving road safety in town and cities have increased recently, due to development of motoring. Local authorities are facing the dilemma of how to decrease the number of road accidents through the use of various traffic calming devices. Moderate traffic calming devices are used on throughways crossing towns with higher permissible speeds and occasional pedestrian traffic. One of such divided streets in Szczecin was narrowed on both sides by the introduction of traffic separators and U-21 road sign. The authors conducted a series of speed and road noise measurements of the street. Measurements were performed at the same traffic volume levels to assess changed road conditions and probably changed acoustic climate. The paper presents speed measurement results along the applied road narrowing and acoustic maps before and after the application of road narrowing on both sides. The narrowing resulted in non-uniform speed changes along the device. Only motorists in the inside lane, moving along heavy vehicles on the outside lane, reduced their speeds. The presented Leq measurement results of road noise along the road narrowing on both sides, on divided road, showed that the narrowing did not produce rapid changes of road noise levels. Differences of ΔLeq noise levels at successive test sections in the vicinity of the narrowing were 1-2.5 dB(A). Analysis of the applied traffic calming devices of slight lane narrowing (0.5-0.6 m) was conducted. It showed that although speed changes occurred compared to the period before the narrowing had been introduced, the narrowing was not effective and can be used only at preliminary stage, i.e. before more restrictive measures of traffic calming may be introduced. It is crucial, however, that since the narrowing was introduced no road accidents involving pedestrians have been reported so far.