Impact of the dedicated infrastructure on bus service quality: an empirical analysis

An econometric analysis is conducted to quantify the impact of different variables on the service quality of the Santiago, Chile bus system. The indicators tested as measures of service quality are the average bus speed, the bus trip time coefficient of variation and the bus headway coefficient of variation. The analysis uses peak hour data obtained for all the routes served by the system's various concessionaire operators. A separate multiple linear regression model is estimated for each indicator, with the latter as the explained variable. The main explanatory variables are a series of design factors representing different types of dedicated route infrastructure and the incorporation in some routes of segments of urban motorway. The results of the models show that the existence of dedicated bus route infrastructure positively impacts all three service quality indicators. The use of motorway segments in particular has a major positive effect on average speed. The model estimates also reveal that the main explanatory factor in headway variability at the end of a route is the headway variability at the start of it, the latter factor determined by operator management decisions regarding bus despatches.