Mobile marked and unmarked speed cameras: their time and distance halos and relative effectiveness in reducing speeds.

Mobile speed cameras were deployed at an urban 50 km/hr speed limit site, an urban 70 km/hr speed limit site and a site on a rural two lane, two way road with a 100 km/hr speed limit. Both unmarked vans and marked camera vehicles were used. Speeds were measured in the vicinity of the sites with and without the presence of camera vans. The extent of time and distance halo effects was investigated as was the effectiveness of marked and unmarked camera vans in reducing speeds. Both marked and unmarked cameras, as they were used at the locations surveyed are effective in reducing speeds in their immediate vicinities with evidence that marked cameras were more effective at the urban (50km/hr and 70km/hr limits) sites. There was little difference in effectiveness between marked and unmarked deployments at the rural (100 km/hr location).The study indicated a time halo of around an hour in the urban sites while speeds began to increase when the camera deployment terminated at the rural site. The best estimates of a distance halo are around 500 metres for the urban sites and 1 kilometre for the rural site. There was no strong evidence that halo effects differed between marked and unmarked vehicles.