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Study uses infrared sensors to count bicyclists, pedestrians on Minneapolis trails (USA)

In June 2011 the Univesity of Minesota's Centre for Transportation Studies reported on a research project which is using infrared counters to measure how bicycle and pedestrian trails are used in the City of Minneapolis. 

In an effort to provide transportation decision makers with more information on nonmotorized transportation facilities, a team of researchers from the Humphrey School of Public Affairs at the University of Minnesota is conducting a study on the use of bicycle and pedestrian trails in the City of Minneapolis. Using infrared counters, the team is collecting data on when and how often these trails are used.

The ITS Institute-funded project is led by Greg Lindsey, professor and interim dean of the Humphrey School. Lindsey and his team are using the data they collect to develop more sophisticated models for estimating nonmotorized traffic on Minneapolis streets, sidewalks, and trails. Their models are helping policymakers and planners make better decisions about how, when, and where to invest in nonmotorized infrastructure.

The team installed seven infrared devices in Minneapolis from June to December 2010: three on the Midtown Greenway, two at Lake Calhoun, two at Lake Nokomis, and one at Wirth Park. When a passing cyclist or pedestrian breaks the infrared beam spanning the trail, the event is registered on an electronic counter. According to Lindsey, this is an unobtrusive way to measure how many people are using a given trail and at what times of the day traffic levels are highest.

The three infrared sensors on the Midtown Greenway are positioned near Minneapolis Department of Public Works bike counters, which are magnetic devices in the trail that register an event when a bike travels over them. Placing both types of counters at the same locations has allowed the research team to test and compare the two measurement technologies.

Each type of counter has limitations, according to Lindsey. Magnetic devices will not register pedestrians because the detectors are not designed to detect the small amount of metal typically on a person, while infrared sensors systematically undercount because they cannot detect if two or more people are traveling side by side. To account for the infrared sensor error, the research team used field observations to develop equations that adjust the data.

Data collection is planned to continue indefinitely at all seven locations, Lindsey said. As more data are collected, the researchers hope to gain a clearer understanding of how variables like weather and time-of-day affect trail use. Additional data will also help researchers examine how the use of trails and bike lanes varies depending on the presence of nearby employment opportunities or the land-use mix in a given area. This information could help decision makers invest in infrastructure where it will be most heavily used.

The data collected by the sensors may also affect trail management in the short term, Lindsey said, citing traffic control changes on the Midtown Greenway as one example. When the trail was developed, there were stop signs on the trail, and vehicles on the streets intersecting the trail had the right-of-way. When traffic counts revealed that non-motorized traffic on the trail exceeded auto traffic on the cross streets, some of the stop signs were reversed. Trail users were given the right-of-way at certain intersections, and vehicles on the cross streets had to stop.

Ultimately, the new models of nonmotorized traffic will provide transportation planners with tools to make more informed choices about investing in new bicycle and pedestrian facilities and reduce the amount of customized work needed for individual projects. “Traffic counts are a basic building block for decision making,” Lindsey said. “They provide evidence to make transportation decisions rationally.”

From the University of Minnesota Centre for Transportation Studies Research E-News June 2011