Minimize technical issues encountered with integrating ITS components by planning for issues and developing solutions prior to project implementation.
TriMet’s experience with the deployment of Transit Tracker in Portland Oregon.
In the case of the Transit Tracker project, the Tri-County Metropolitan Transportation District of Oregon (TriMet) encountered several technical issues that were addressed successfully during project deployment. TriMet was faced with several technical issues and the following solutions were developed during project deployment.
- Comply with ITS standards and protocols to provide vendor and system flexibility. Compliance to standards and protocols can help to ensure that ITS components being integrated are compatible with each other and can function together. In TriMet’s case, no Transmission Control Protocol/Internet Protocol (TCP/IP) standards for the LED electronic sign display interface had yet been developed, so they had to work with sign vendors with proprietary protocols. Even though no standards were available, TriMet knew they wanted to interface with TCP/IP and they provided specifications that required the sign vendors to interface with the protocol. TriMet had originally purchased a couple of different types of signs, but the proprietary sign interfaces were difficult to integrate and they did not provide adequate communications between the signs and the central processor, so eventually those signs were taken out of service. There are some proprietary standards that are easier to work with and they were able to find two different sign manufactures that could interface with the Orbital TMS (Transportation Management System) software being developed for the project. These are the signs that are currently in service. There are actually four signs sold by different venders that support Orbital software so TriMet does have some flexibility in regards to which signs they use.
- Similar standards issues also applied to TriMet’s radio channel and other communication methods they were interested in implementing. TriMet believes that there was an advantage to using TCP/IP and standard protocols that would allow the use of different communication methods, yet retain the same applications. Complying with ITS standards and protocols helps to ensure a modular and compatible infrastructure.
- Consider communication infrastructure issues based on system size, current technology, system costs and system requirements.One of the system architecture issues for TriMet was identifying the communication protocol to be used between the central system and the LED sign displays. TriMet had their own radio frequency bandwidth, but the costs to interface with this communication system made this solution unfeasible in the early stages of the project. The first phase was a prototype phase that deployed a small number of signs and provided the central system. Future phases would expand the network. TriMet chose to use Cellular Digital Packet Data (CDPD) communication to provide a communications connection for their electronic displays. With CDPD communication, a monthly fee is charged to provide bandwidth. That type of communication is cost efficient when the system is small and does not have many signs that require communication connections. However, as the system grew and more signs were installed, more bandwidth was required. CDPD proved to be unstable, was being phased out, and the fees began to increase. Newer technologies were being proposed by AT&T, but that would require system integration at least two more times. It then became more cost efficient for TriMet to reconsider moving over to their own bandwidth.
- For Phase 1, TriMet looked at their existing infrastructure and the capital costs required to upgrade and based on the size and system requirements of the prototype system decided that it would be more cost efficient to consider outside sources for communication. However, as their system grew and technology changed they decided that using their own communications infrastructure was the more efficient way to expand the system.
- Consider integrating with existing legacy systems to save costs associated with implementing a new system. Oftentimes, one of the biggest hurdles when developing ITS systems is to make them compatible with existing systems already in place. The Transit Tracker project was no exception. This project builds upon the existing AVL bus dispatch system (BDS) and the rail central control system (CCS), disseminating real-time transit information collected through the BDS and rail CCS systems to transit customers. In TriMet’s case they did not encounter many problems integrating the Transit Tracker system with the existing legacy system. The existing systems were built on the same platform that was being proposed for the Transit Tracker system. This saved software development time and system costs. There were a few minor changes that needed to be addressed because of the different requirements necessary for reporting information to customers as opposed to reporting information to the dispatchers. As an example, for the real-time Transit Tracker system, TriMet had to change the rate at which information is provided and expand the type of information provided by the system to respond to the needs of the customer.
- Be consistent and comply with standards where possible when facing incompatible hardware/software issues. Using TriMet’s experience, they believe the best approach to keeping hardware/software compatibility issues at a minimum was to be as consistent and comply with standards where possible. Technology changes so quickly that it is often the case that the lag time between the system design and implementation is such that the requirements will change by the time the system is deployed. The system may start with one communications interface and processor and by the time it is completed, that processor may be obsolete and need to be replaced. The further the technology advances beyond the legacy system, the harder it is to interface successfully with that system. These issues usually significantly affect the cost and the schedule of deploying a project. Standards and open protocols will minimize these issues and should be used when available to limit the additional costs and time required to implement, test and debug the system.
This lesson suggests that agencies may not be able to eliminate all technical issues encountered with integrating ITS components that may occur; however, planning for issues and developing solutions prior to project deployment may help to minimize issues. Technical issues that occur during implementation can be very costly and may have significant impact on the budget and schedule for the project. Providing solutions in the planning stages will reduce the issues that may occur during implementation, provide the agency with better information for scheduling and budgeting the project, and prepare the agency to handle unanticipated issues more effectively.
Author: David Evans and Associates, Inc
Published By: ODOT and Tri-Met
Source Date: 4/1/2004URL: http://www.oregon.gov/ODOT/HWY/ITS/PDFs/ITSDocuments/ OR0206TransitTrackerSelfEvaluation.pdf
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