Vehicle probe technology is emerging as a means of monitoring traffic without the need for deploying and maintaining equipment in the right-of-way. In contrast to speed sensors, which log the velocity of the vehicles passing a fixed point, vehicle probes directly measure travel time by comparing the location of a vehicle at different points in time.
Commercial traffic-data services are emerging based on vehicle probe methods. The most common probe methods are cell-phone probes or GPS probes. Cell-phone methods rely on the cooperation of cellular carriers to mine the timing and handoff data emanating from the cellular tower switching network.
GPS probe methods rely on data obtained from automated vehicle location (AVL) systems using Global Positioning System (GPS) technology. AVL systems are common in trucking fleets and are beginning to spread to taxi, bus, delivery and other types of fleets. Early demonstrations of probe technology relied heavily on a single method, technology or data source. Current offerings combine information from multiple probe sources as well as data from existing fixed-sensor networks into a comprehensive traffic-information service.
The vehicle probe data market is fueled by the high cost of deploying and maintaining fixed-sensor networks and the growing demand for comprehensive traffic information from travelers and transportation agencies. The proliferation of low-cost wireless data communications is whetting consumers’ appetites for accurate, real-time congestion information. Timely reporting of incidents and road closures allows drivers to optimize their routes and take alternative routes to avoid delay.
The I-95 Corridor Coalition is a partnership of state departments of transportation, regional and local transportation agencies, toll authorities and related organizations, including law enforcement, transit and port and rail organizations. The partnership area ranges from Maine to Florida (including the District of Columbia) with affiliate members in Canada.
I-95 Corridor Coalition members work together to reduce congestion, increase safety and security, and ensure that the entire transportation network supports economic vitality throughout the system. In order to achieve the coalition’s mission of “working together to improve multimodal transportation services in the region through information sharing and coordinated management and operations,” the coalition initiated a regional traffic-monitoring project in 2006 based primarily on vehicle probe technology.
The project established a system that will act as a continuous source of real-time transportation-system status information along a major portion of the corridor. The data from the system will drive multiple coalition applications related to traveler information and performance measurement, as well as support a myriad of other internal engineering and planning applications at member agencies.
Required for proposal
In early 2007, the I-95 Coalition released a request for proposals (RFP) to procure a traffic-monitoring system within the corridor. Critical requirements of the monitoring system are summarized as follows:
- No particular probe technology was specified. The approach is limited only to methods that do not require additional physical equipment to be located in the right-of-way. Vendors are encouraged to propose innovative probe-based approaches while taking advantage of data from existing systems that rely on field assets, such as loops, radar or toll-tag systems;
- Data quality specifications were determined based on its intended use. The specs limit the error in reported speed (and associated travel time) under varying roadway conditions;
- The accuracy of traffic data will be independently validated. Payment is contingent on validated accuracy;
- The vendor retains ownership of the data for resale in commercial markets. The coalition retains rights to the data to support all intended applications, and member agencies retain the right to use the data for all internal applications in perpetuity. Restrictions are placed only on the extent, form and granularity of the data that can be released to the public or shared with other private entities;
- Vendors must be able to support ITS standard protocols and deliver data to the coalition using open and published data formats;
- The initial contract is for three years, with options to renew for an additional seven years;
- Coverage will include I-95, beltways, parallel freeways, parallel signalized arterials, cross-linking freeways and cross-linking arterials. The coalition’s intent is to designate a system of roadways that contribute to interstate through movement and provide opportunities to divert between parallel facilities when incidents and congestion occur; and
- Coalition members may expand system coverage within their own jurisdictions through the contract.
References (provided by the vendor) were contacted to corroborate vendors’ claims of quality and accuracy. Due to the uncertainties of deploying cutting-edge technology as well as adopting new business models, vendors were required to submit a plan to manage project risks. The RFP was issued on April 27, 2007. Proposal evaluation concluded in December 2007 when a multiyear contract was awarded to a team headed by Inrix Inc.
Inrix uses a method to fuse various data sources into a comprehensive picture of traffic flow. The dominant source of data is fleet systems that use GPS tracking to monitor vehicle location, speed and trajectory. Inrix’s proposed technical approach appears capable of providing quality traffic data on all freeways as specified in the RFP.
Traffic data on the initial core systems, which span New Jersey to North Carolina, is expected by July 1, 2008. A periodic and ongoing data-quality-validation program is currently under development.
Opening up arteries
Inrix, Kirkland, Wash., also provides an innovative approach to obtain quality traffic data on arterials. No probe-based technology has been demonstrated to date that can provide traffic data on arterials to the level of accuracy specified for freeway networks. During the initial three years of the contract, Inrix will provide traffic data on 1,000 miles of arterials within the core system. Inrix and the coalition will work together during the initial three-year period to assess the accuracy, the timeliness and the application potential of the arterial traffic data.
The initial deployment, referred to as the “core network,” is a network of approximately 1,500 miles of freeways and 1,000 miles of arterials spanning New Jersey to North Carolina. These states intend to integrate the data into their existing operations soon after the system begins operation. The core network reflects the primary routes that contribute to interstate movement along the corridor and provide cross-links between major through facilities in the event of incidents or heavy congestion.
The I-95 Corridor Coalition is moving forward with an aggressive program to procure travel-time and speed data as a pure traffic-data service for the coalition and its members. When operational in mid-2008, this service will provide a comprehensive traffic-monitoring system without the need for additional fixed sensors in the right-of-way.
By specifying the quality of data, the ownership and the dissemination rights needed to support coalition and agency applications, vendors were given the freedom to propose innovative solutions with minimal constraints. By pooling the resources of several states, this project attempts to bridge jurisdictional boundaries in order to provide long-distance travelers with information relevant to interjurisdictional highway travel. Additionally, this project will provide the information needed to support implementation of long-distance diversions that are characteristic of major incidents that disrupt traffic in multiple states.
Member agencies will benefit by receiving traffic-flow information to support external applications such as 5-1-1 systems, display travel times on variable message signs and manage traffic during incidents, as well as all internal applications.
The success of this project is a showcase of the fundamental shift from agency-owned, application-specific data-collection systems toward vehicle-probe-based, outsourced data procurement that supports multiple applications, spans large geographical areas and bridges jurisdictional boundaries in order to provide travelers and agencies the information needed to efficiently navigate and manage our highway system.
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