Use of AVL Technology to Optimize Transit Service Restoration Strategies

The objectives of this research project are to assess the effectiveness of techniques of service restoration used in certain bus routes at Chicago Transit Authority (CTA), to understand the pros and cons, as well as the conditions of using different service restoration techniques; and to make recommendations or rules on when to use what techniques under what conditions. The goal is to reduce service interruptions and improve bus service reliability by making better use of transit technologies like Automatic Vehicle Location (AVL), Automatic Passenger Counter (APC) and wireless communications. Reliable service is essential for transit agencies to attract and maintain passengers and for customer satisfaction. Unfortunately, there are many factors detrimental to reliable transit services, such as weather, traffic, road construction, and scheduling, insufficient maintenance, and personal issues of operators. These factors often lead to unreliable services like bus bunching, schedule deviation, and large headway gaps. Service restoration is a process of restoring service to its scheduled time and/or headway by using different techniques such as single-headway hold or the Prefol hold. Traditionally, service restoration is handled by deploying a team of supervisors in the field to monitor, maintain, and restore bus services. But, as well documented in the literature, these field supervisors do not have real-time information about what is going on beyond their visual observations, and there is no or poor communication between bus operators, field supervisors and dispatchers in the control center (Pangilinan, 2006). For example, the field supervisor has no access to real-time information on bus operations downstream. This lack of information and poor communication has prevented field supervisors from doing their job of maintaining and restoring reliable services. Some service restoration techniques have also been proposed to restore services, such as schedule-based holding for low frequency routes and headway-based holding for high frequency routes (Turnquist, 1981). However, due to lack of real-time information, some strategies are very difficult to implement. Furthermore, there is very limited empirical research on how effective these strategies are under different conditions (Strathman et al., 2001). The deployment of transit technologies like AVL and APC has provided us an opportunity to address these problems, because they provide bus location information in real time. But the question is how to best to use the information to assess the effectiveness of these technologies, and more importantly how to use the AVL information to aid the field supervisors and dispatchers in selecting strategies and techniques to maintain or restore service reliability under different situations of service disruption.