Above: Framework for the evaluation of various sensor network configurations and algorithms.
By Josh Allen, Program Specialist, Illinois Center for Transportation
A recently completed project sponsored by the Illinois Department of Transportation (IDOT) and conducted by the Illinois Center for Transportation investigated the effectiveness of sensor network systems for detecting traffic jams or stopped traffic, estimating travel times and delays for motorists, and estimating speed of vehicles in and approaching roadway work zones.
The study relied on computer simulations of two work zones calibrated with data gathered from sensors in actual Illinois work zones. The goal was to offer information to help IDOT improve its decision-making process when implementing smart work zone systems, in order, according to Work, “to maximize their potential safety and mobility benefits for the drivers in our state.” Li adds, “Smart work zones are viewed as a promising solution, yet we currently lack a fundamental understanding of how to improve their effectiveness while balancing cost and performance, which motivated this project.”
The researchers faced two key challenges in this project. They were, as Li states, “the large quantity of smart work zone configurations that need to be evaluated and the difficulty in gathering necessary data, including field traffic data and cost data of existing work zones.” To overcome these obstacles, Work and Li ran a series of microsimulations. These simulations allowed them to test a large number of smart work zone configurations. According to Work, this allowed them to answer questions such as “How does the sensor spacing impact our ability to estimate travel times? and How much can the accuracy be increased, or the cost reduced, by improving the estimation algorithms or changing the sensor type?” While simulations take time to run, it is still much cheaper than trying to test these configurations in the field.
Work and Li’s simulations showed a number of potential ways to maximize safety at work zone sites. These findings still require field verification, but could represent a cost savings of smart work zone technology deployments. They found that real-time microwave sensors provide more accurate measurements than radar and low-energy radar sensors and that the existing technology seemed sufficient for accurate results—assuming optimization of the algorithms that interpret the data. However, they also found that the technology for estimating real travel times in work zones performed poorly because of the lack of technology able to predict changes in the traffic conditions necessary for good travel time estimates.
Lorton noted several key findings, stating, “This research project yielded some valuable information regarding optimization of sensor density as well as the inherent limitations of certain types of sensors, which will allow IDOT to provide better guidance to design engineers and to make modifications to special provisions for smart work zone monitoring systems.” Lorton is hopeful that future field work will verify the results of microsimulations performed under this project.
While this research gives a promising direction to the subject matter, there is still work to be done to fully maximize the value of the project. Li notes that “the findings in the project suggest a low-cost wireless sensor network (which can be densely deployed within a reasonable budget) is beneficial.” He projects that the next stage of work is testing their simulation results in the field to determine the real world impact.
Work adds, “Now that we better understand the trade-offs, the next step includes validation of the findings on active work zones. Ultimately, we hope to transition our findings into practice so that IDOT can continue to deploy these technologies as inexpensively and reliably as possible.”
Originally published 1/20/2017 by the Illinois Center for Transportation