Evaluation of the effect of fixed speed cameras on speeding behavior among Iranian taxi drivers through telematics monitoring.

Objective: Installation of speed cameras is a common strategy to reduce over-speeding; however, there is evidence that their efficacy in speed reduction is limited to the proximity of the camera. This study aimed to evaluate driving speeds in relation to the position of cameras among Iranian taxi drivers.

Methods: Speed data were collected from April 2020 to January 2021 via telematics devices (using on-board computer, gyroscope, and GPS) installed on taxis in southern Tehran, Iran. All drivers were males above 20 years of age. Throughout the study, taxi drivers were not changed. Eligible road segments were selected based on: a) not containing any obstacle that would cause speed reduction; b) having ≤5 entry/exit points; c) absence of park and ride or taxi stations; and d) availability of at least 5,000 datapoints. The average speed was compared between the camera- and non-camera zones. Camera zone was defined as the area within 300 meters of the speed cameras.

Results: The telematics system included 2,644,846 datapoints gathered from 50 taxis. Two highways' segments with three lanes in each direction were included: Tehran-Varamin (18 taxis, 18,978 datapoints) and Ghadir (17 taxis, 8,203 datapoints). On both highways, speed was significantly lower in the camera zones (Tehran-Varamin: 84.9 ± 12.2 km/h versus 86.7 ± 13.7 km/h;  = 0.005; Kolmogorov-Smirnov test (KS)  < 0.001/Ghadir: 68.7 ± 13.7 versus 73.1 ± 11.3;  = 0.008; KS  < 0.001), indicating a V-shaped distribution of speed near the position of cameras (Presence of Kangaroo effect). Drivers were more likely to exceed speed limits in the non-camera zones compared to camera zones (Tehran-Varamin: 14.6% versus 8.4%/Ghadir: 23.1% versus 17.3%). This effect of the cameras was consistently observed in a subgroup analysis based on time of day (daytime versus nighttime).

Conclusions: Among Iranian taxi drivers in southern Tehran, average speed was significantly lower in the vicinity of speed cameras, suggesting the presence of camera manipulation. Alternative speed control interventions are required to improve the safety of the taxi service.