Archived operational ITS data is a rich source of information for a range of transportation functions including policy and planning, monitoring system performance and the variability of performance, and identifying and diagnosing defective components. The Portland Regional Transportation Archive Listing (PORTAL), activated in July 2004, is located at portal.its.pdx.edu within the Portland State University (PSU). PSU is designated as the region's official data archiving entity, and has a direct fiber-optic connection to the Oregon DOT (ODOT).
PORTAL archives data from the 436 inductive loop detectors in the Portland area's advanced traffic management system (ATMS) and ramp metering system. The detectors, located on ramps and upstream of on-ramp locations, capture vehicle count, average speed, and utilization (the percentage of the sample period when a vehicle was over the detector). The data was only used for operational and real-time purposes prior to the implementation of PORTAL, with the raw data being discarded after a short period of time. Now, PORTAL enables users to access and query the archived data through a web interface, and analyze the data for transportation planning, administration, and research purposes.
A paper on the Portland Regional Transportation Archive Listing (PORTAL) reveals the steps involved for a successful implementation of an ITS data archive, which include several of the following recommendations.
- Ensure that the archive adheres to the recommendations of the National ITS Architecture for the Archived Data User Service (ADUS). The PORTAL fulfills the major processing functions of ADUS as outlined in the national architecture, as summarized below.
- Store data in the same format as received from ITS subsystems.
- Accommodate levels of aggregation and reduction of data.
- Sample raw data flows for permanent storage in accordance with user specifications.
- Apply quality control procedures, including flagging suspect data and editing data.
- Distinguish between unprocessed (raw), edited, aggregated, and transformed.
- Consider using a regional ITS coordinating organization as platform on which to build regional partnerships. Archived data has many beneficiaries, but historically archiving has been the domain of a single agency that has informal arrangements with users. However, advances in web-based services and data management tools however create the possibility for users to access large data sets remotely from their own workstations. One of the challenges of implementation is determining who will bear the responsibility and cost of maintaining an ITS data archive. The agencies that produce the data may use it for operational real-time purposes, and may not have a need to access archived data. In the case of PORTAL, metropolitan planning organizations (MPOs), transit operators, a port, state DOTs, and a university cooperated through the auspices of TransPort, the regional ITS coordinating organization. TransPort also facilitated the development of the region's ITS architecture.
- Consider using an academic organization deeply involved in transportation research as the responsible entity for the data archive. PSU is a major user of regional ITS data for transportation research, and operates in cooperation with the ODOT, TriMet (the transit provider for the Portland metropolitan region), and the city of Portland. TransPort views PSU as being in an ideal position to host transportation data in its Intelligent Transportation Systems Laboratory. The laboratory is designated as the regional archiving site for ITS data from Portland and adjacent areas of southwestern Washington state. An added benefit is that PSU researchers who have experience working with ITS data have facilitated the use of the data by ADUS stakeholders including the Metro, the Portland regional planning organization.
- When developing an archive, realize that effective archiving systems have frequently started as small prototypes using a single data source, and that detector data are among the most useful archived data. Research indicates that detector data are the most useful archived data. As the archive stabilizes and at the appropriate time, consider adding data from additional sources. PORTAL initially archived detector data. Other candidate sources include computer-aided dispatch from the incident management system in Portland's ATMS, and transit bus data that includes automatic vehicle location via Global Positioning System (GPS), automated passenger counters, and bus schedule adherence data.
Archived ITS data is a multimodal resource for monitoring system performance, understanding causes for performance variation, identifying maintenance problems, and determining policy and planning. The successful implementation of an archive system, as demonstrated by PORTAL, provides valuable lessons learned and guidelines for future ADUS projects.