Does the measured performance of bus operators depend on the index chosen to assess reliability in contracts? An analysis of bus headway variability

Document Type

Journal Article

Publication Date


Subject Area

place - south america, place - urban, mode - bus, operations - reliability, operations - frequency, operations - performance, planning - service quality, organisation - regulation, organisation - contracting, technology - geographic information systems, technology - ticketing systems


Bus contract, Reliability, Bus dispatching, Bus bunching, Quality of service, Transantiago


The choice of performance indicators in bus contracts is a complex problem for public transport regulators and financial incentives to provide a reliable service have been designed by several agencies. We study the issue of bus headway variability, focusing on headway variability at bus dispatching, which is a very relevant issue that has not been properly analysed in existing studies, despite the considerable influence of irregular dispatching on bus bunching. We identify the variables that are statistically significant in explaining bus headway variability at the beginning of routes, using large GPS and smartcard databases of all bus routes in Santiago, Chile. Three measures of headway variability are used: standard deviation, modified index per observation and an ad-hoc measure included in the Santiago bus contracts, called ‘minutes of incidence’. Significant variables to explain headway variability are bus frequency, number of bus services per terminal, distance from the bus depot to the first stop, route length, bus demand and operating speed. The measured performance of each bus operator is different depending on the headway variability indicator used, which points to the relevance of choosing an appropriate index of service reliability as a financial incentive in contracts. Implications for service planning are discussed.


Permission to publish the abstract has been given by Elsevier, copyright remains with them.


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