A multi-university research team involving University of Arizona transportation planning expert Arlie Adkins applied that question to the yielding behavior of motorists at crosswalks to examine potential racial bias. And, with a new $30,000 grant from the National Institute for Transportation and Community, the researchers have begun investigating the influence of gender-based bias on drivers' stopping behavior.

In the original investigation -- the first known field experiment of its kind -- the team found that African-Americans experienced a wait time about 32 percent longer than for whites before drivers chose to yield. The team also found that African-Americans were twice as likely as white pedestrians to be passed by multiple vehicles.

"We were surprised at just how stark the difference was," said Adkins, an assistant professor in the UA School of Landscape Architecture and Planning and a transportation planning expert, noting that the team controlled for age, clothing and other socioeconomic factors of the pedestrians.

"It was not a very large study, so we weren't sure the amount of data collected would be enough to reach statistical significance, so we were surprised to see how quickly the significance showed up," Adkins said. "Drivers were clearly displaying behaviors consistent with implicit racial bias."

Findings from the study -- involving 88 pedestrian trials and 173 driver-subjects -- were published in August by Transportation Research Part F: Traffic Psychology and Behavior in the article, "Racial Bias in Driver Yielding Behavior at Crosswalks." Adkins co-authored the article with Portland State University researchers Kimberly Kahn, an assistant professor of social psychology and principal investigator on both NITC grants, and Tara Goddard, a doctoral candidate in urban studies at Portland State. The trio began working together while Adkins completed his doctorate at Portland State.

"It's nice to have this cross-university collaboration," Goddard said. "We are really excited about building on psychological theory and social psychology, applying both to transportation domains that are clearly relevant to people's experiences and actual physical safety."

Studying Implicit Bias

Combining expertise in urban transportation and planning with social psychology enabled the team to study discrimination and the possibility of implicit bias, which references the various unconscious stereotypes and beliefs people hold that shape how they think and act.

"We are not saying drivers are overtly racist," Kahn said, emphasizing that the study results are consistent with implicit biases that individuals may hold beneath their awareness against certain groups of people.

"Improving the pedestrian experience is not just going to be an engineering problem," she said. "You have to bring in psychology to get a deeper understanding of the issues we are trying to solve."

Comparable questions about implicit bias have been posed by researchers studying why people of certain backgrounds are medically misdiagnosed in greater numbers, have more difficulty having their resumes seriously considered for potential jobs and even struggle to hail a taxi.

"These subtle forms of stereotyping are pervasive across society, and the majority of Americans hold some level of subconscious bias or association just by growing up in this culture," said Kahn, an expert in implicit stereotyping, biases and discrimination.

"That's what makes contemporary forms of bias so pernicious -- we may not be aware that we have these biases," she said. "That's where implicit bias comes from in the first place. So, you can think you're just driving to work and won't even notice that you were differently stopping for one pedestrian over others."

With the new funding, the team has this month begun the new 18-month project conducting field research in Portland. While studying the possibility of gender bias, the team will expand its study of racial bias while also studying the influence of crosswalk design and signage on yielding behavior. The team also will capture data on the race and gender of drivers. Thus, the study will involve men and women and individuals who are African-American and white at two different types of crosswalks.

"Cars don't drive themselves and, as humans, we are somewhat flawed in our processing, especially in the roadway environment where there are a lot of distractions and we are moving at much higher speeds," Goddard said.

"A lot of information processing is involved, which means we may fall back on automatic processing quite a bit," she said. "Clearly, there is so much work to be done everywhere with racism and discrimination. The more we deal with that on a systematic level, the greater chances we have in terms of long-term impacts."

Disparity Indicated by Data

Motivating the team's research is nationwide data indicating a disparity in pedestrian injuries and fatalities.

The National Highway Traffic Safety Administration this year reported that 4,735 pedestrians were killed in traffic crashes in 2013, representing 14 percent of all traffic-related fatalities. The agency estimated that 66,000 pedestrians were injured that same year. The U.S. Centers for Disease Control and Prevention also reported that during a period that spanned 2000 to 2012, African-American and Hispanic male pedestrians were more than twice as likely then white men to die in traffic crashes.

Kahn said experiences with subtle forms of discrimination could then result in individuals altering their transportation choices. That is also true about the pedestrian experience, she said.

"You can imagine how, if you are constantly experiencing these disparities, you might choose to avoid walking or force the right of way when cars are not stopping, potentially putting yourself in dangerous situations," Kahn said. "That may play into these shocking statistics."

Goddard and Adkins said their work carries numerous implications for public safety and urban planning, particularly in informing planners and engineers on ways to improve spaces used by pedestrians and motorists. The team also hopes to initiate a larger investigation in cities across the country, and eventually to help improve public awareness around pedestrian safety.

"We want this work to continue, and it will be very important to see if there are disparities in other parts of the country," Adkins said.

"While implicit bias does not explain the disparity in safety outcomes, it may be a contributor," he said. "These microaggressions in different contexts add up to become a very negative situation for some people. It is a problem if people feel threatened, or if they are treated unequally."