Incorporate real-time bus and train location information in the Connection Protection algorithm.
Experience of the Utah Transit Authority in implementing a Connection Protection program for rail-to-bus passenger transfers in Salt Lake City.
Made Public Date


United States

Evaluation of Utah Transit Authority's Connection Protection System


The Utah Transit Authority (UTA) implemented a Connection Protection (CP) system to improve the reliability of transfers from the higher frequency light rail trains to the lower frequency bus services at selected connecting rail stations. The CP system examines the status of trains and issues a "hold at {station name} until {time}" message to buses waiting at the connecting rail stations via the bus' onboard Mobile Data Terminal (MDT), if the lateness of train is within a pre-determined time threshold. The system was completed and tested in January 2002 prior to the Winter Olympic Games in Salt Lake City. Operationally, the CP messages are triggered by the late train events. One late train could potentially trigger multiple CP messages to hold one or more buses at each of the next three down-line stations, based on the CP assignment. An evaluation was conducted to assess the performance of the CP system and the response of passengers and system operators. This lesson is based on experience with the early operation of the CP system with the objective of identifying potential improvements and offering guidance to other transit agencies elsewhere that may be considering implementing a similar system.

Lessons Learned

UTA's CP system algorithm integrates both train and bus schedule data, taking into account estimated train arrival time, train schedule, real-time train position based on Global Positioning System (GPS), and bus schedule to determine whether a late train would potentially jeopardize bus connections at down-the-line stations. While train on-time performance can be assessed and forecast with good accuracy, only some of UTA's buses are equipped with Automatic Vehicle Location (AVL)/GPS. Thus, schedule adherence of buses cannot be identified on a real-time basis. The CP algorithm, therefore, must rely upon static bus schedules rather than known real-time bus locations, compare the static bus schedule information with identified late train events, and then determine whether or not to issue a "hold until" message to buses at a particular station.

While UTA was planning to implement AVL/GPS on their entire fleet, at the time of the project's evaluation, most did not have this capability. UTA's experience with implementing their Connection Protection system in the absence of accurate real-time bus location information suggests the following guidance:

  • Consider scenarios that may not need a CP message. When buses are running late, a CP message may not be needed. When a train makes up lost time, a CP message may not be needed if no prior "hold until" message was issued. When a later bus on a given route can more efficiently pick up passengers from a prior late train, a CP message may not be needed. Almost two-thirds (64%) of all CP "hold until" messages received by the UTA bus operators were reported to have been unnecessary. Unnecessary CP messages could presumably occur because: the train made up time and, hence, was not late enough to cause missed connections; or because no train showed up after the bus operator waited the requested time period; or because no riders transferred to the bus; or because the bus was running behind schedule and could pick up late train passengers without further delaying the bus. Many of these kinds of unnecessary CP messages could be avoided if the CP algorithm had access to up-to-the-minute accurate information on both train and bus locations.
  • Equip every train and bus to be covered by the system with AVL. Due to the lack of real-time bus location information for most of the buses in UTA's system, the CP algorithm was not able to consider actual bus status in its computation. Real-time knowledge of the exact location of every train and bus could be incorporated into the CP algorithm, resulting in much more accurate CP messaging. Incorporating the real-time location of the train and bus into the CP algorithm would potentially reduce unnecessarily issued CP "hold until" messages by at least 50 percent, based on the UTA evaluation findings.

Efficient and accurate issuance of CP messages is expected to enhance customer satisfaction and encourage higher CP compliance by bus operators. Although UTA's train and bus riders are largely unaware of the CP program, it has served as a useful tool that can help UTA operators better meet the needs of their transit customers. The evaluation of this system identified the importance of accurate knowledge of both train and bus locations, and incorporating this information on a real-time basis into the CP algorithm. A well-designed CP system helps achieve ITS goals to enhance efficiency, mobility, productivity and customer satisfaction.