An overview of traffic control schemes for freeway systems

Some of the criticalities associated with traffic phenomena in freeway networks can be mitigated or even eliminated with suitable control strategies. The most important and evident drawback of traffic is surely congestion and, consequently, congestion reduction is one of the main objectives of traffic control policies. More recently, other control objectives have become relevant, including reduction of fuel consumptions and pollutant emissions, number of accidents, noise and so on. Researchers have investigated traffic control approaches for some decades and are still working on developing control schemes that, on the one hand, are more and more effective for improving the performance of the traffic system and, on the other hand, are easily implementable in real contexts.