Longitudinal annoyance responses to a road traffic noise management strategy that reduced heavy vehicles at night.

A traffic management strategy was designed to reduce trucks using an urban corridor. The intervention had potential to affect night-time truck flows, but did not target truck traffic in the day, or vehicles other than trucks at any hour. A two-year long panel study measured the community's response to this intervention, using five repeated measurements of response. There were significant reductions in the panel's response to noise, both for night-time annoyance and for interference with activities. This was remarkable given that noise monitoring showed that the intervention produced no change in conventional traffic noise indicators. However, there were measureable changes in the number of articulated truck movements at night, and the benefit can be attributed to reduction in the number of noise events from heavy vehicles. The parallel tracking of changes in reported noise effects and the numbers of heavy vehicles in the night hours in this longitudinal study provides strong support to the notion that noise effects at night depend on the number of noise events experienced, not only on the overall level of traffic noise. The latter appear to be unresponsive indicators by which to assess the noise-effect benefit of heavy vehicle reduction strategies.