Beware that modeling may not be a suitable substitute for before-after studies of ITS integration projects.
Experience from Minnesota's Traveler Information Guidance and Emergency Routing (TIGER) Project.
An independent evaluation of the project assessed the safety and mobility impacts of the deployments by determining the number and severity of vehicle crashes, and speed and travel time. However, the evaluation effort was challenged by the lack of clear "before" and "after" conditions. Despite these challenges, the evaluation identified preliminary lessons learned of importance for similar projects, as follows.
- Beware that modeling as a tool for assessing mobility impacts from ITS deployments may incur significant costs and have considerable limitations. The evaluation plan initially called for a "before-after" study of mobility performance measures of the mobility impacts on the corridor of the project deployments. However, there was no clear "before" or baseline condition because ITS technologies existed on the corridor before the project launch. Complicating the "after" condition was the staggered and at times interrupted deployment schedule, as well as the dynamic conditions of the corridor arising from a rapidly growing region that was placing increased demands on I-94 and Highway 10. Nonetheless, it is highly desirable for project stakeholders and the public to have an estimate of the mobility impacts on the corridor from the project deployments. Faced with unclear "before-after" conditions, the evaluation team initially recommended using modeling to evaluate safety and mobility impacts. However, a careful review of available models revealed significant limitations associated with each of them, and the likelihood of incurring substantial costs to modify existing models or develop a new model. Finally, the evaluation team concluded that modeling was not workable for this project. The alternative proposal was to assess mobility by evaluating driver behaviors during incident conditions, primarily through collecting and analyzing detector data to estimate diversion rates. To assess safety impacts, the evaluation team recommended using incident and accident logs to compare the number of accidents before and after the deployment of TIGER components.
- Capitalize on the learning opportunity created by the coordination required in multi-jurisdictional and multi-agency deployments. The preliminary evaluation of the TIGER project revealed that the project partners gained increased awareness and understanding of the needs of partnering agencies. This outcome was unexpected but proved to be beneficial by increasing the situational awareness of the different partners in regards to other partners' needs. For example, Mn/DOT staff developed a stronger understanding of the needs of the Highway Patrol during enforcement activities, and in turn, the Highway Patrol gained insight into the implications of their enforcement and incident investigation activities on traffic management.
- Be aware that ITS deployments can provide unexpected and unplanned benefits to law enforcement. The project partners described two experiences in which the surveillance system provided benefits to law enforcement. In one case, patrol vehicles were in pursuit of a high-speed motorcycle traveling along the I-94 corridor. The patrol vehicles were unable to keep pace with the motorcycle, but the surveillance cameras tracked the suspect vehicle, eventually finding an opportunity for patrol cars to be prepositioned in time to successfully apprehend the suspect. In the second example, a patrol officer pulled his vehicle over to assist a disabled vehicle on the roadside. Finding that the disabled vehicle was not occupied, the officer determined that the vehicle had been stolen. In coordination with the dispatcher, the officer checked the camera feed from a nearby interchange and sighted the presence of individuals walking toward a truck stop. The dispatcher monitored the individuals, who were attempting to get gas to refuel the car, until another patrol officer arrived and the suspects were arrested.
- Be aware that unanticipated circumstances can lead to a reassessment of project priorities and deployment goals. The TIGER project included the much anticipated deployment of a remote platform with mobile closed circuit television (CCTV), dynamic messaging signs (DMS), and a detector station. The plan called for the platform to be stationed in the corridor where the need was greatest. An unexpected turn of events occurred when the I-35 bridge collapsed in August 2007, compelling Mn/DOT to re-deploy the remote platform from the corridor to the bridge for the purpose of supporting traffic management. As of 2008, Mn/DOT had reported that the platform was performing well in providing critical traffic management capabilities since the closure of the I-35 bridge.
The Minnesota TIGER project was a complex technical and institutional effort, requiring the integration of existing and new ITS technologies and the coordination of different agencies. The preliminary evaluation found that the deployment provided unanticipated benefits for different agencies, from an increase in situational awareness of the needs of other agencies, as well as the supporting role surveillance technologies can have in law enforcement. The evaluation also found that determining the mobility and safety outcomes of the ITS deployments is not necessarily feasible. The experience in Minnesota demonstrates that before-after studies or modeling may have significant shortcomings and may not provide a viable approach for determining impacts of a deployment. Nonetheless, as demonstrated by the findings, the Minnesota ITS integration project has produced benefits that support safety and mobility.
Author: Doug Sallman, Robert R. Sanchez
Published By: US DOT- ITS Joint Program Office
Source Date: 14 May 2008
EDL Number: 14454
Other Reference Number: DTFH61-96-C-00098; Task SA61029URL: http://ntl.bts.gov/lib/30000/30600/30645/14454.pdf
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Major Initiatives > Cooperative Intersection Collision Avoidance Systems
Major Initiatives > Integrated Corridor Management Systems
Major Initiatives > Integrated Corridor Management Systems
Major Initiatives > Emergency Transportation Operations
Other Program Activities > Public Safety
Other Program Activities > Rural ITS Deployment
CCTV, closed circuit television cameras, road monitoring, camera imaging, sensors, vehicle detector, traffic detection, traffic monitoring, congestion monitoring