In recent years interest has grown for granting priority to bus within signals control, by the developments of the technologies in computer, communication sensors, and Automatic Vehicle Locating (AVL). But in the cases with heavier traffic, even if dynamic locations of bus are exactly known, when no dedicated bus lanes are provided buses may still be involved in the general traffic flow, sometimes having to suffer heavy time losses. Here, the concept of Intermittent Bus Lane (IBL) is introduced: this is a lane whose status changes according to the presence or not of a bus in its spatial domain: when a bus is approaching such a section, the status of that lane is changed to BUS lane, and after the bus moves out of the section, it becomes a normal lane again. The IBL signals are co-operated with normal traffic signals at the intersections. This will ensure that privileged lane status only for the time strictly needed for the bus to run through it with less delays, and the normal traffic does not suffer much. This paper presents the concept and structure of IBL system, its signal settings, the movements of vehicles and buses on IBL and how its interfaces are connected with the normal traffic controllers to obtain useful vehicle and bus messages and transmit IBL signal control parameters, as well as the controls of integrated system on a new objective function. Several models are also constructed, based on the methods of some typical urban traffic control systems. Finally some simulation results are presented, showing the advantages for buses and small influences to general traffic flow when IBL signals are applied.
Abstract