Transportation agencies throughout the United States have begun implementing advanced parking information systems with the goal of increasing customer satisfaction and improving traffic operations. Through the use of variable message signs (VMS), these systems provide motorists with real-time information about parking availability at appropriate decision points on their route so that they can make an informed decision about where to park.
To determine the benefits of transit applications of parking management systems, the United States Department of Transportation's (USDOT) ITS Joint Program Office and the Federal Transit Administration (FTA) conducted a national evaluation of two of the first transit parking management systems deployed in the United States. One system serves two Metra commuter rail stations in Chicago, Illinois, while the other serves a Metro Station in Montgomery County, Maryland.
The parking management system in Chicago, Illinois monitors parking utilization at two adjacent Metra Stations with the use of loop detectors and conveys this information to motorists via eight VMS located at key decision points along expressways and arterials near the stations. The Montgomery County system monitors parking utilization at the Glenmont Metro Station with the use of video detection and conveys information to motorists via three VMS located near the station.
Depending on the type of communications technologies used, the project team should consider conducting a field study to ensure that there are no unforeseen field conditions that could affect system communications. In the case of the Chicago project, the team elected to use unlicensed radio frequency to support wireless communications between select system components since much of the area was undeveloped at the time and it was more economical to make use of wireless communications than to bury cable.
This technology has sufficed with the exception of a few minor problems experienced initially due to streetlights interfering with the system line-of-sight. Interference could have been a more significant problem had the team not conducted a Radio Frequency Field Study prior to deployment. This study detected some unforeseen field conditions which resulted in unexpected costs to the project. It was found that a highway vehicle weigh station located in close proximity to the communications tower would cause radio frequency interference. To address this problem, repeater poles were installed to provide an uninterruptible, seamless wireless communication link between the various system components. Although additional costs were incurred, the Chicago Regional Transportation Authority (RTA) and Metra identified the source of the interference early enough in the construction process to enable them to undertake corrective actions that would minimize the cost and time impacts. It is expected that costs would have been higher if the issue had been discovered after the system was in place.
The evaluation of Chicago's advanced parking information system provides the following valuable insight for other agencies considering deployment of similar ITS technologies:
- Expect that topographical encumbrances and other radio transmission interferences could require additional equipment and result in higher costs to achieve full communications capability. In the case of the RTA/Metra project, a requirement for a Radio Frequency Field Study was specified as part of the contract with the General Contractor performing the system installation and testing, and this study did uncover obstacles. Identifying these challenges early in the design process allowed the team to modify the design early on, and avoided surprises later.
- Be aware that unique capital requirements resulting from unforeseen field conditions are quite a common reality for ITS applications. Despite the fact that the Chicago project team conducted a field study prior to system design and installation, they still experienced a few minor problems initially due to streetlights interfering with the system line-of-sight. Installation of repeater poles solved this problem, but was an added unexpected cost.
This lesson recommends that it is important to conduct a study of the surrounding area for topographical encumbrances and radio interference when deploying a project relying on radio frequency communications technology. The RTA/Metra team found that conducting such an assessment early in the construction process detected unforeseen field conditions which would have added additional costs after construction and delayed the final deployment. The lessons learned above, if applied in designing new systems, are expected to improve operational efficiency at transit parking facilities.