Intermittent Bus Lane System: Demonstration in Lisbon, Portugal

The concept of Intermittent Bus Lane (IBL) was introduced by Viegas (1996) as an innovative approach to achieve bus priority. The IBL consists of a lane in which the status of each section 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, open to general traffic. Therefore when bus services are not so frequent, general traffic will not suffer much, and bus priority can still be obtained. The theoretical development of the IBL has already been concluded, though which the relationships among bus messages, general traffic flow and the related IBL signals and normal traffic signals are established. Also a simulation of the concept has been developed, and its results suggest that average bus traveling times can be reduced by as much as 30% with small decrease in the general traffic average speeds. Besides these results a real world demonstration was considered necessary to act as a prototype. This paper describes the demonstration carried out in Lisbon, in cooperation between the University, the Municipality and the urban bus operator (CARRIS), for a period of 6 months starting on September 2005. The main results obtained reveal an overall increase of 5 to 20% in the bus average speed, with very limited impacts to the general traffic movements.