Empirical Evidence of Speed Management Effects on Traffic Flow at Freeway Bottleneck

摘要

Since speed was recognized as the most important contributory factor in fatal road crashes, speed managementhave been widely implemented in several countries in order to improve road safety. Thus, Automated SectionSpeed Enforcement System is being increasingly used as an effective way to tackle speeding especially onmotorways and in tunnels. However the effects on traffic flow patterns of such systems is still controversial.Therefore, in this work it is presented an empirical analysis of traffic flow patterns Before-After theintroduction of such a system along a freeway section with recurrent congestion. Data gathered consisted both inpoint measurements at detectors and in Average Travel Speeds of each individual vehicle crossing the stretch.Main observed features were i) a strong homogenization of individual speeds and of mean speeds among thelanes, ii) a reduction of the strength of the bottleneck with a consequent iii) increase in the amplitude and theperiod of the oscillations of traffic characteristics iv) a sensible reduction of travel times also during thecongestion pattern (in apparent contradiction with point measurement results) caused by the moving of thebottleneck downstream of the section.Empirical evidence suggests that mutual benefits in terms of both road safety and traffic efficiencywould be produced by the concurrent application of such enforcement systems with dynamic speed limitstrategies.