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An Observational Study of Pedestrian and Bicycle Crossing Experience in Two Modern Urban Roundabouts

John Hourdos, Director, Minnesota Traffic Observatory, and Adjunct Assistant Professor, Department of Civil Engineering, University of Minnesota

September 29, 2011

Responding to reports that pedestrians and cyclists were finding it difficult to cross roundabout intersections, the Minnesota Department of Transportation (MnDOT) asked researchers at the Minnesota Traffic Observatory (MTO) to take a close look at interactions between motor vehicles, pedestrians, and cyclists. MTO director John Hourdos highlighted some interesting findings from the project at an ITS Institute Advanced Transportation Technologies seminar on September 29.

Two sites were selected for the project—one in a suburban setting with a high volume of vehicle traffic, and another near a public park in Minneapolis. The City of Richfield, where the suburban site is located, was a key partner in the project. The two sites differ in terms of road geometry, traffic control features, and traffic characteristics, allowing the researchers to compare and contrast different roundabout situations.

The researchers used a mobile data collection system, designed by MTO lab manager Ted Morris, that consists of eight cameras mounted atop an extendable mast that continually recorded vehicles and pedestrians entering and leaving the intersections. The camera mast was attached to a trailer, which also housed a battery power source that allowed the unit to operate for nearly a month without recharging. Back at the lab, students carried out the painstaking work of combing through the data and logging every interaction between a pedestrian or cyclist and a motor vehicle for statistical analysis.

Hourdos explained that identifying factors that affected drivers’ decision to yield was one of the project’s principal objectives. The researchers looked at a wide variety of possible influencing factors, including whether the driver was entering or leaving the roundabout, the presence of other vehicles behind and in front of a target vehicle, the positions of other vehicles in the roundabout, time of day, volume of traffic, and the number and location of pedestrians and cyclists waiting for an opportunity to cross.

Several factors appeared to influence the willingness of a driver to yield. Drivers who were exiting a roundabout were significantly less likely to yield. However, drivers at both sites were more likely to yield to pedestrians standing in the center of the roundabout than to those waiting outside the intersection. In addition, drivers were more likely to yield to larger groups of pedestrians and cyclists. Overall, drivers at the Richfield site—where traffic volumes are higher and pedestrians and cyclists are fewer—were far less likely than drivers in Minneapolis to yield the right of way.

Analyzing the delay times experienced by pedestrians and cyclists produced some interesting results, Hourdos said. Taking into account all pedestrians—both those who had to wait to cross and those who did not encounter any vehicular traffic at the intersection—the average delay was around 2.3 seconds, and even those who had to wait for a car to stop waited an average of only 3.8 seconds. However, there was a huge variation in wait times, with some having to wait up to 30 seconds or longer. Compared to a signalized intersection, where the average delay is roughly half the time it takes for the signal to complete one full cycle, roundabouts offer much better average wait times, Hourdos said. But having to stand at the crosswalk while cars speed through (despite a state law requiring drivers to yield) could make the wait seem much more onerous, Hourdos noted.