Study Details

Study Title: Effects on Speed and Safety of Point-to-Point Speed Enforcement Systems: Evaluation on the Urban Motorway A56 Tangenziale di Napoli

Authors: Montella, et al.

Publication Date:FEB, 2005

Abstract: In this paper, we evaluated the effects on speed and safety of the point-to-point (P2P) speed enforcement system activated on the urban motorway A56 in Italy. The P2P speed enforcement is a relatively new approach to traffic law enforcement that involves the calculation of the average speed over a section. To evaluate the speed effects, we performed a before-after analysis of speed data investigating also effects on non-compliance to speed limits. To evaluate the safety effects, we carried out an empirical Bayes observational before-and-after study. The P2P system led to very positive effects on both speed and safety. As far as the effects on the section average travel speeds, the system yielded to a reduction in the mean speed, the 85th percentile speed, the standard deviation of speed, and the proportion of drivers exceeding the speed limits, exceeding the speed limits more than 10 km/h, and exceeding the speed limits more than 20 km/h. The best results were the decrease of the speed variability and the reduction of the excessive speeding behaviour. The decrease in the standard deviation of speed was 26% while the proportion of light and heavy vehicles exceeding the speed limits more than 20 km/h was reduced respectively by 84 and 77%. As far as the safety effects, the P2P system yielded to a 32% reduction in the total crashes, with a lower 95% confidence limit of the estimate equal to 22%. The greatest crash reductions were in rainy weather (57%), on wet pavement (51%), on curves (49%), for single vehicle crashes (44%), and for injury crashes (37%). It is noteworthy that the system produced a statistically significant reduction of 21% in total crashes also in the part of the motorway where it was not activated, thus generating a significant spillover effect. The investigation of the effects of the P2P system on speed and safety over time allowed to develop crash modification functions where the relationship between crash modification factors and speed parameters (mean speed, 85th percentile speed, and standard deviation of speed) was expressed by a power function. Crash modification functions show that the effect of speed on safety is greater on curves and for injury crashes. Even though the study results show excellent outcomes, we must point out that the crash reduction effects decreased over time and speed, speed variability, and non-compliance to speed limits significantly increased over time. To maintain its effectiveness over time, P2P speed enforcement must be actively managed, i.e. constantly monitored and supported by appropriate sanctions.

Study Citation: Montella, A., L.L.Imbriani, V. Marzano, and F. Mauriello. "Effects on speed and safety of point-to-point speed enforcement systems: Evaluation on the urban motorway A56 Tangenziale di Napoli". Accident Analysis and Prevention, Vol. 75, (2015) pp. 164-178.


CMFs Associated With This Study

Category: Advanced technology and ITS

Countermeasure: Install automated section speed enforcement system

CMF CRF(%)QualityCrash TypeCrash SeverityRoadway TypeArea Type
0.68325 StarsAllAllPrincipal Arterial Other Freeways and ExpresswaysUrban
0.9514.93 StarsAllAllPrincipal Arterial Other Freeways and ExpresswaysUrban
0.51248.84 StarsAllAllPrincipal Arterial Other Freeways and ExpresswaysUrban
0.56343.75 StarsSingle vehicleAllPrincipal Arterial Other Freeways and ExpresswaysUrban
0.79120.95 StarsRear endAllPrincipal Arterial Other Freeways and ExpresswaysUrban
0.77622.44 StarsOtherAllPrincipal Arterial Other Freeways and ExpresswaysUrban
0.78421.65 StarsAllOPrincipal Arterial Other Freeways and ExpresswaysUrban
0.63236.85 StarsAllK,A,B,CPrincipal Arterial Other Freeways and ExpresswaysUrban
0.70429.65 StarsOtherAllPrincipal Arterial Other Freeways and ExpresswaysUrban
0.42757.34 StarsOtherAllPrincipal Arterial Other Freeways and ExpresswaysUrban
0.70629.45 StarsOtherAllPrincipal Arterial Other Freeways and ExpresswaysUrban
0.49150.94 StarsWet roadAllPrincipal Arterial Other Freeways and ExpresswaysUrban
0.66633.45 StarsAllAllPrincipal Arterial Other Freeways and ExpresswaysUrban
0.71528.55 StarsAllAllPrincipal Arterial Other Freeways and ExpresswaysUrban
0.62437.65 StarsAllAllPrincipal Arterial Other Freeways and ExpresswaysUrban
0.83116.94 StarsAllAllPrincipal Arterial Other Freeways and ExpresswaysUrban
0.79220.84 StarsAllAllPrincipal Arterial Other Freeways and ExpresswaysUrban
0.9138.74 StarsAllAllPrincipal Arterial Other Freeways and ExpresswaysUrban
0.71428.64 StarsAllAllPrincipal Arterial Other Freeways and ExpresswaysUrban
0.47352.74 StarsSingle vehicleAllPrincipal Arterial Other Freeways and ExpresswaysUrban
0.9910.94 StarsRear endAllPrincipal Arterial Other Freeways and ExpresswaysUrban
1.097-9.73 StarsMultiple vehicleAllPrincipal Arterial Other Freeways and ExpresswaysUrban
0.88124 StarsAllOPrincipal Arterial Other Freeways and ExpresswaysUrban
0.74325.74 StarsAllK,A,B,CPrincipal Arterial Other Freeways and ExpresswaysUrban
0.81818.24 StarsAllAllPrincipal Arterial Other Freeways and ExpresswaysUrban
0.48951.14 StarsAllAllPrincipal Arterial Other Freeways and ExpresswaysUrban
0.83816.24 StarsDry weatherAllPrincipal Arterial Other Freeways and ExpresswaysUrban
0.44555.54 StarsWet roadAllPrincipal Arterial Other Freeways and ExpresswaysUrban
0.84715.34 StarsDay timeAllPrincipal Arterial Other Freeways and ExpresswaysUrban
0.61738.34 StarsNighttimeAllPrincipal Arterial Other Freeways and ExpresswaysUrban
0.81194 StarsAllAllPrincipal Arterial Other Freeways and ExpresswaysUrban
0.74264 StarsAllAllPrincipal Arterial Other Freeways and ExpresswaysUrban