PSU reseachers found bike boxes may contribute to less traffic incidents
By Sharon E. Rhodes
Published: Thursday, February 11, 2010
Updated: Thursday, February 11, 2010
Last year, the City of Portland installed 10 bike boxes—seven of which are painted bright green—in the hopes of preventing future right-hook accidents, such as those in which two bicyclists died in 2007.
To determine the efficiency of the bike boxes, the City of Portland partnered with researchers at Portland State who are part of the Oregon Transportation and Research and Education Consortium. The team’s preliminary research suggests that the bike boxes improved both the perceived and actual safety of bicyclists and motorists.
Dr. Christopher M. Monsere, assistant professor of civil and environmental engineering, and Dr. Jennifer Dill, OTREC director and associate professor of urban studies and planning, led the bike box study. Nathan McNeil, a master’s student in urban and regional planning and OTREC student of the year in 2009, also worked on the project assisting Dill and Monsere both with the study’s design and the analysis.
According to the surveys collected, 77 percent of cyclists surveyed feel that bike boxes make cycling safer. Dill established the importance of bicycle infrastructure and perceptions of safety in encouraging people to travel via bicycles in OTREC’s 2008–09 annual report.
Researchers looked for conflicts between motorists and cyclists in video footage and categorized each as either a minor, substantial or major conflict. They found two major conflicts: those in which the cyclist had to use some sort of quick evasive maneuver in order to avoid a collision, and five substantial conflicts. In all, there were 20 conflicts before the installation of bike boxes and only 14 since.
Monsere said that after adjusting for the number of cyclists—1,471 before the bike boxes compared to 2,301 since—there were significantly fewer conflicts after the installation of the bike boxes at most of the intersections studied.
“One thing that surprised me a bit at first was that many right turning cars took a narrower turn [i.e., went closer to the curb] after the bike boxes had been installed—part of the reason for this may be that, with the bike boxes, the bicycle lanes don’t go all the way to the intersection,” McNeil said.
Monsere said they based the bike box study on two experimental traffic-control devices: the sign near the bike boxes that depict a yield sign and cyclist on a strip of green, and the bike boxes with a green bike-lane strip preceding and succeeding each bike box.
The green lane is “supposed to make [motorists] more aware of bikes,” Monsere said.
According to a survey given to motorists, 89 percent of motorists surveyed prefer the green-colored bike boxes to those that consist only of a white outline. Also, 43 percent of motorists surveyed feel the bike boxes make driving less convenient at the intersections, while 55 percent believe the bike boxes make drivers more aware of bicyclists generally.
“Critics say it does nothing to prevent right hook [accidents] on green,” Monsere said. However, the preliminary research shows that “it most likely hasn’t made things worse, [but it] most likely has made things better.”
While the current research does not definitively show that bike boxes prevent right-hook accidents, they do keep both cars and bikes out of crosswalks, Monsere said.
Two sources of data—video from cameras set up at intersections with and without bike boxes, and surveys given to both bicyclists and motorists—were analyzed.
“I spent a number [of] rush hours out on street corners giving postcards to passing cyclists directing them to the online survey,” McNeil said.
The City of Portland solicited motorists via e-mail.
Although the cameras collected 918 hours of video, time constraints forced researchers to select only six hours of video from each intersection.
“It took myself and two other students 3 to 4 hours per hour of video to collect all of the data on cars, bicycles and pedestrians at each intersection to get all our data and examine how they interacted,” McNeil said.
Unfortunately, a dearth of data limited the conclusions that researchers could draw.
“It’s just not a lot of data,” Monsere said. “If the City does go ahead and implement more bike boxes, [they will] set up cameras differently, so that we could see cyclists’ head turns [and other movements].”
The researchers did not have as much control in the experiment as they might have wished. For instance, Monsere said that the quality of the video changed before and after the bike boxes were installed and that cameras were not set up in a way that allowed researchers to see traffic signals and whether or not pedestrians were present.
Asked whether motorists and bicyclists may have struggled with the unfamiliarity of the bike boxes, Monsere said, “There probably was a learning curve, but [it was] probably pretty short.”
Monsere said that in some places, experimental bicycle infrastructure confuses drivers, who mistakenly drive around something that transportation officials had intended them to drive through.
“Portland is the first city in the U.S. to have this many bike boxes,” Monsere said.
Currently, Austin, Texas, Tuscon, Ariz., and New York City, N.Y., are working to install their own bike boxes.
“They have an advanced stop bar for cars about 15 feet before the intersection, with a stencil of a bicycle in the space in front of cars—however that area is regular pavement and not colored. The bike boxes in Portland definitely catch your eye more than those in New York,” McNeil said, who recently visited New York.
There are also bike boxes in Europe.
“[In London] they call them advanced stop lines, they are almost identical, but they used red and are provided for left turns,” Monsere said.
Though some believe that what works well in Europe may not work in the U.S., McNeil conducted preliminary research on similar forms of bicycle infrastructure such as those found in Denmark, New Zealand, and England and related studies.
In London, 53 percent of all vehicles stopped before the advanced stop line, according to www.westminstercyclist.org.uk.
In Portland, however, Monsere said that over 80 percent of all cars that observed stopping did not encroach on the bike box.