This research investigated the effects on traffic volumes, speeds and crashes of traffic calming devices on urban local streets. Eleven sites in Christchurch with street calming devices were evaluated using field surveys and network modelling using TrafikPlan, and compared with findings from a literature review.

The main findings of the studies were: at seven sites that used vertical devices for treatment, five of them had reduced traffic volumes and speeds; at ten sites that used horizontal devices, eight of them had experienced reductions in volumes and speeds; from the crash history, it was found that road safety has been noticeably improved after installation of the traffic calming devices, with average crash reductions of 15-20%; in terms of network performance, TrafikPlan modelling seems promising for estimating traffic volume and speed changes on treated local streets and adjacent arterial roads. This paper will discuss these findings and speculate on how the devices investigated affect traffic behaviour. It is recommended that further research be conducted at more sites and for longer time periods to build up a comprehensive local database of traffic calming treatments. Future studies should also investigate the effectiveness of environment impacts of the devices, i.e. noise and air pollution.