Travel Time on Arterials and Rural Highways: State-of-the-Practice Synthesis on Rural Data Collection Technology
To assess state–of–practice and identify lessons learned from experience, a literature search was conducted. The following lessons highlighted experience from a deployment in Minnesota where a real-time travel time information system was implemented to improve travel during roadway improvements on a 70 mile section of I-35 from Hinckley to Duluth, Minnesota. Using commercial off the shelf (COTS) software (TrafAlert™), MnDOT posted travel times on eight dynamic message signs (DMS), and a website with an online map. The following lessons were gathered from MnDOT staff and partners at the conclusion of the project in 2012.
- Avoid unnecessarily restrictive requirements and ambiguous terms in bid documents. MnDOT requirements focused more on performance outcomes rather than detailed design specifications. This gave the contractor more ability to innovate and optimize the system. It was noted, however, that additional details in the design specifications for some aspects of the system such as sensor spacing and detection capabilities could have improved system performance. The project staff acknowledged there were tradeoffs between cost and system performance.
- Require contractors to provide detailed quality control documents that outline how they will set up and test the system and monitor and correct issues. The methods and criteria that the transportation agency plans to use to verify travel time data accuracy should be specified to contractors during the bid process so that they can assess the validity of the methods and the potential risks of not meeting performance criteria. The verification method should include multiple assessments at different times and days.
- Avoid penalization for inconsequential issues. The MnDOT contract initially stated that monetary deductions would be assessed against the contractor if any part of the system was not functional, but was later revised to state that deductions would only occur if the nonfunctional component adversely affected travel times. This revised language provided contractors with an incentive to design a robust system.
- Provide motorists with travel time information prior to decision points to allow them to make effective routing choices. Feedback from travelers indicated that they would have liked to receive the travel time information before passing an exit to a viable alternate route.