Traffic regulation is one of the concerns of road and rail engineers. In the first case, the aim is to reduce the causes of accidents. In the second case, the aim is to reduce unplanned downtime. In any case, we are looking to make better use of the taxiways. Road traffic theory is mainly concerned with saturated regimes when vehicles drive one after the other in a flow that is similar to a fluid flow. In this book we discuss free diets where vehicles are independent of each other and the transition from free to saturated diets. This concept of real-time intelligent signal can be implemented on any section of road provided that visibility has been recorded throughout that section. The theory of rail traffic is linked to signaling. It determines the state of traffic balance by blind obedience to signals from mechanics. . The TRAC system thus makes it possible to vary the length of the track sections provided that there is signaling in the cab and to avoid waiting at the red light,thus making better use of the line. These two studies are published together because they deal with the same subject and we thought it would be interesting to combine asphalt and rail way.