Bastian Schroeder shows off a new photo on his computer desktop: “Have you seen this one? It’s a roundabout in Germany: Two lanes, single entry, single exit, with a bike lane tunnel.”

He admires the idealistic German traffic scene with the enthusiasm of a kid planning a model railroad, but Schroeder is a doctoral student in civil engineering, and his work simulating traffic dynamics at roundabouts impacts pedestrian safety and air quality as nearby as Hillsborough Street.

In November, Raleigh voters approved a bond referendum that included $3 million for Hillsborough Street improvements.

The money is likely to be used for the construction of roundabouts, a form of intersection control that eliminates traffic signals and left turns, Eric Lamb, transportation services manager with the City of Raleigh Public Works Department, said.

City Council will decide in June whether and where to build Hillsborough Street roundabouts based on public input.

“One goal of roundabouts is to make Hillsborough Street a destination,” Nagui Rouphail, professor at the Institute for Transportation Research and Education, said. “You slow it down, make it attractive for people to stop; to want to go to those businesses by reducing traffic and allowing safe pedestrian crossings.”

George Chapman, chair of the Hillsborough Street Partnership, said Hillsborough Street is one of the most dangerous streets in the state for pedestrians.

“It’s the fact that you have a couple thousand plus students crossing the street in conflict with 15 to 20,000 cars per day,” Lamb said. “There are a lot of people who don’t follow the rules. I witnessed a pedestrian accident on Hillsborough [Street]. This woman attempted to cross the street without waiting for the signal. The car didn’t even brake until after they hit her.”

Maybe that accident would have been avoided if signals had been obeyed, but according to Rouphail, traffic signals may actually exacerbate Hillsborough Street’s safety issues.

“When you have traffic lights, there is a lot of red-light running going on, and acceleration to catch the light,” he said. “There are no geometric features to cause drivers to slow down.”

With roundabouts, a smooth flow of traffic is maintained at 15 to 25 miles per hour without stoplights, as entering traffic yields to cars already circulating.

Roundabouts have a record of reducing crashes in problem areas. In a study of 11 U.S. intersections, conversion to roundabouts reduced the annual crash rate by 37 percent and annual injuries by 51 percent, according to an online publication of the U. S. Department of Transportation Federal Highway Administration.

Another advantage to smooth traffic flow is reduction of automobile emissions, hence, improved air quality.

“Most emission occurs when you have stopping and acceleration,” Rouphail said. “It’s not just your travel; emissions are episodic. At a roundabout, you only yield, you don’t have to stop, so emissions are decreased due to the smooth profile of deceleration and acceleration.”

The Institute for Transportation Research and Education plans to monitor the effect of roundabouts on vehicle emissions by driving Hillsborough Street routes in a vehicle equipped with a portable emissions detector before and after the construction.

Roundabouts are not, however, without a downside.

“It’s not like it’s a nirvana,” Rouphail said. “There are problems with roundabouts. On the exit side, it’s trickier. And there are issues with blind pedestrians.”

This is where Schroeder’s work comes in.

“We are looking at a toolbox of treatments to make roundabouts safe for blind pedestrians,” Schroeder said. “Things like yield signs, pedestrian-activated signals, raised crosswalks and textured pavement would provide auditory signals or ways for blind pedestrians to orient.”

Schroeder programs computer simulations to test the effects of various roundabout treatments on traffic flow and pedestrian behavior.

“This is the great thing about simulations,” he said. “We can figure out the details before we put these things out on the street and make people mad or cause an accident.”

Others have expressed mixed feelings about the plans to build roundabouts on Hillsborough Street.

“I’ve seen roundabouts in other places, in Europe and Israel, and they work fine,” Dorit Eliyahu, a doctoral student in entomology, said. “I like it because you don’t have to wait a long time for the light.”

In 2003, Eliyahu was in a car accident while making a left turn onto Hillsborough Street. She had a green light, but didn’t see another vehicle was coming straight across the intersection.

“That kind of accident wouldn’t happen at a roundabout,” she said,” But if people haven’t encountered them before and don’t know what to do, this could also be a problem.”

Coby Schal, professor of entomology, pointed to driver confusion at the Pullen-Stinson roundabout when it was built in 2002.

“Everybody better go to roundabout driving school,” Schal said. “When they built that roundabout on Pullen, nobody knew what to do; they stopped. The whole point of a roundabout is to yield and keep moving. And people lost a lot of hubcaps on that inner curb.”

Chapman, however, said the project is about more than just roundabouts.

“Roundabouts are just part of a more comprehensive approach to community revitalization,” he said. “Right now, Hillsborough [Street] is seen as a border between communities. We want it to be seen as a place where the communities meet.”