A method to calculate commercial speed on bus corridors

This paper presents a macroscopic simulation method for the operation of a public transport corridor. The method includes enough detail to take into account all sources of delay, which mainly include running time and signal and stop delays. We use up-to-date traffic theories to describe these sources of delay and ad hoc models to decide the optimum stop spacing. Outputs of the method include the commercial (mean) speeds of public transport vehicles as well as their delays at each road element. The method has been validated against real data from a busway in Santiago de Chile showing an average commercial speed discrepancy of less than 1%. The impact of various traffic measures has been tested with the model, including the optimum stop spacing, the number of berths, the availability of overtaking facilities at stops, and signal timings; all of these factors consider the progression of public transport vehicles. As a result, we have found that commercial speeds can be improved by 9 to 20% if stops are optimally spaced. A further 2 to 7% increase in speed can be achieved if overtaking facilities are provided at stops. If traffic signals are set such that they take into account bus progression, an additional 3 to 5% increase in commercial speed can be attained. In summary, the method developed in this work is more accurate than simplified analytical models yet less complicated than microscopic simulations, in terms of ability to assess traffic measures toward improving public transport operations.