Index numbers for monitoring transit service quality

• Monitoring service quality over time can help to improve the service.
• Index numbers proved a practical tool for evaluating service quality evolution.
• Simple index numbers emerged as a useful tool for measuring the variation of each service aspect.
• Composite index numbers turned out suitable for the multidimensional service quality construct.
• Transport practitioners can easily monitor service quality through the index numbers.

The measurement of transit service quality is very important for guaranteeing a transport supply characterized by satisfactory service levels for the passengers. Even more important is the monitoring of the levels of service quality over time, which can be very useful to determine if the goals established by the transport planners are being met or exceeded. The status and evolution of transit service quality can be monitored through periodic and regular updating of the opinions expressed by the passengers about the service during the well-known Customer Satisfaction Surveys, allowing the effect of policies to be evaluated and specific interventions to be introduced. In this work, just the issue of monitoring service quality based on users’ opinions is approached, and the index numbers usually applied in the economic and industrial field are proposed for this purpose. Index numbers permit to study the fluctuations or variations of a variable or more variables over time, providing a powerful measurement for making comparisons and predictions of the analyzed concept. The index numbers were calculated on the basis of data collected from Customer Satisfaction Surveys addressed to the passengers of the metropolitan public service of Granada (Spain). The analyzed time period has been established from 2007 to 2013. Interesting results derive from the calculation of the index numbers. Since both perceptions and importance rates are considered in this methodology, the results can inform, not only on the satisfaction tendencies but also on the trend on customers’ priorities, which is actually the expected quality. Therefore, policies could more efficiently be designed to adjust the service to the users’ real needs.