Green solutions have made lofty claims in the last few decades but they have been optimistic hope more than reality. Simulations from the University at Buffalo may change that; they say it's possible for drivers to cut their tailpipe emissions without significantly slowing travel time. 

In computer models of traffic in Upstate New York's Buffalo Niagara region, they found that green routing could reduce overall emissions of carbon monoxide by 27 percent for area drivers, though they did it by increasing the length of trips an average of 11 percent. 

Still, simple changes can yield great gains. Funneling cars along surface streets instead of freeways helped to limit fuel consumption and intelligently targeting travelers - rerouting one fifth of drivers who would benefit most from a new path - reduced regional emissions by about 20 percent. 

Green routing is appealing is because it's a strategy that consumers and transportation agencies could start using today.  You just have to be someone who doesn't mind traveling longer.  But instead of being more heavy-handed rules that only apply to non-government workers, GPS navigation systems and online maps could promote green routing by giving drivers the option to choose an environmentally friendly route instead of the shortest route. 

"We're not talking about replacing all vehicles with hybrid cars or transforming to a hydrogen-fuel economy -- that would take time to implement," said Adel Sadek , an associate professor of civil, structural and environmental engineering at the University at Buffalo. "But this idea, green routing, we could implement it now." 

The researchers tied together two computer models, the Motor Vehicle Emission Simulator (MOVES), created by the Environmental Protection Agency, which estimates emissions, and the Transportation Analysis and Simulation System (TRANSIMS), which simulates traffic in great detail, taking into account information including the location and pattern of signals, the grade of the road and the trips people take at different times of day. 

After incorporating Buffalo-specific data into TRANSIMS, they ran a number of simulations, rerouting travelers in new ways each time. After running the models numerous times, the researchers reached a "green-user equilibrium", a traffic pattern where all drivers are traveling along optimal routes. With the system in equilibrium, moving a commuter from one path to another would increase a user's overall emissions by creating more congestion or sparking another problem. 

The simulations were part of a broader study Sadek is conducting on evaluating the likely environmental benefits of green routing in the region. His project is one of seven that the U.S. Department of Transportation has funded through a Broad Agency Announcement that aims to leverage intelligent transportation systems to reduce the environmental impact of transportation.

Sadek and Liya Guo, a PhD candidate, presented their research on green routing at the 18th World Congress on Intelligent Transportation Systems in October.