Safety effects of automated section speed control on the Italian motorway network

• Published in: Journal of safety research 2019-06, Vol.69, p.115-123
• Main Authors: La Torre, Francesca, Meocci, Monica, Nocentini, Alessandro
• Format: Article
• Language: English
• Subjects: Accident Prevention - instrumentation; Accidents, Traffic - prevention & control; Accidents, Traffic - statistics & numerical data; Automated section speed control; Automatic control; Automation; Bayes Theorem; Bayesian analysis; Before-after study; Controlled Before-After Studies; Crash modification factor; Crashes; Empirical analysis; Empirical Bayes; Highways; Humans; Injury prevention; Italy; Law Enforcement - methods; Photography - instrumentation; Property damage; Road safety; Speed control; Studies; Traffic safety; Traffic volume
• ISSN: 0022-4375; 1879-1247
• DOI: 10.1016/j.jsr.2019.03.006

Introduction: Automated Section Speed Control (ASSC) has been identified as an effective countermeasure to reduce speeds and improve speed limit compliance. Method: An Empirical Bayes (EB) before-and-after study was performed in this research in order to evaluate the impact of the ASSC system on the expected crash frequency. The study was carried out on a sample of 125 ASSC sites of the Italian motorway network covering 1252 km, where a total of 21,721 crashes were recorded during a 10-year analysis period from 2004 to 2013. Results: Overall, the EB analysis estimated a significant 22% reduction in the expected crash frequency due to the implementation of the ASSC system. The analysis indicated that the effect is slightly larger on property damage only (PDO) crashes (−23%) than on fatal injury (FI) crashes (−18%) and that the highest reductions in crash frequency are expected for multi-vehicle FI crashes (−25%) and multi-vehicle PDO crashes (−31%). Furthermore, the results indicated that the ASSC system is more effective in reducing crash rates when traffic volume increases and it is therefore strongly recommended as a countermeasure to improve safety on high-traffic-volume motorway sections. •An EB before-after study was performed in order to evaluate the impact of the ASSC on the expected crash frequency.•The methodology allows a good transferability of the models and a reliable estimation of the safety effects of the ASSC.•The CMF values are lower than 1 for all crash types when all the traffic conditions are considered together.•The CMFs has been evaluated by using a very large sample size consisting of 1252 km of motorway and 10-year analysis period.•The implementation of the ASSC system led to a statistically significant 22% reduction in the expected crash frequency.