In 2015, the Wisconsin Legislature increased the speed limit from 65 to 70 mph on hundreds of miles of interstate highways. That same year, statewide fatalities attributed to vehicle crashes jumped to 566, up from 506 in 2014, the first significant increase in decades. At first glance, it seems like a simple case of cause and effect.
But much like driving in bad weather, the answer is … not so fast. Funded by state and federal grants, Yue “Troy” Liu and Xiao (pronounced “Shaw”) Qin are researching ways to better understand and manage traffic. The College of Engineering and Applied Science associate professors pore over data pulled from roadside sensors, mobile phones and simple police crash reports, all with the goal of making driving safer, be it in a construction zone or on the open road.
“Crashes can be caused by a variety of reasons,” explains Qin, who’s studying the issue for the Wisconsin Department of Transportation. He thinks a main reason for the 2015 increase in traffic fatalities is that the number in 2014 was so low.
In fact, he says, the number of fatalities had fallen so far since the end of World War II that an increase might well have been expected. “Basically,” he says, “when you hit rock bottom, there’s nowhere to go but up.”
He believes the decline in those years can be attributed to technology, in a variety of ways.
“We have better vehicle technology – smarter cars with better safety equipment that’s more affordable,” Qin says. The roads themselves are safer, too, and there is greater enforcement of traffic laws. He also notes that first responders and other emergency medical staff are more skilled than ever, meaning some serious injuries are less likely to become fatalities.
As of now, there remains no clear verdict on how higher speed limits affected traffic fatalities. “It’s controversial,” Qin says. “Speeding has been a problem for a long time. And speed plays a significant role in injury severity. But there’s no clear evidence that raising the speed limit will lead to more crashes.”
His work is aided by collecting better crash-related data, which allows for better models to determine statistically significant crash factors. Law enforcement authorities are revising the MV4000 form used to document crash sites. “And now,” Qin says, “we’re expanding our analysis to include more human factors – driver behavior, law enforcement effort and even socioeconomic status of the drivers.”
The socioeconomic data helps determine if there’s an association with better safety, even if it’s not a direct correlation. “The families with a higher income can afford new cars, better cars, safer cars,” Qin says. “And their communities may be able to build better roadways with better pavement conditions.”
Liu’s work, focused on improving traffic safety and efficiency related to road construction zones, is also bolstered by advances in data collection.
He’s been awarded a federally funded $1.56 million grant to help create the next generation of work zone management. Governments develop transportation management plans to guide drivers through construction zones, and currently, they do so the way it’s always been done – manually. “That means people base it on their theories,” Liu says. “But we have a lot more useful data, and we can take advantage of the data that’s available.”
In Wisconsin, Liu explains, the state collects data about traffic conditions from thousands of sensors and cameras along highways. “It’s easy for them to streamline the data into their server. And then we have access to this data, so we can do our research to improve traffic management.”
We also carry advanced sensors in our cars, even if we don’t realize it. “A lot of us are using smartphones,” Liu says, “and sometimes, their location data – their trajectories – will be recorded. So, we can understand their behavior, their travel patterns and the travel time they spend on the roads.”
All of this helps inform better design for highways and better traffic management, and there’s a lot at stake from using that data. Large cities like Washington, D.C., can have 700 to 800 construction zones per year.
“It’s pretty important to have a very good system to try to schedule those projects so that we can minimize their impact on the overall [traffic] network,” Liu says. He’s helped the D.C. Department of Transportation implement such a system, and it could be adapted to other congested places, like Chicago – or Milwaukee. A comforting thought the next time you see a “Detour Ahead” sign.