Between car exhaust that pollutes the air and runoff that pollutes waterways, roads can be detrimental to the environment.

A group of transportation, environmental and government leaders gathered at Benedictine University in Lisle Thursday for DuPage County’s sixth annual environmental summit to discuss ways to make the region’s transportation more environmentally friendly.

Jesse Elam of the Chicago Metropolitan Agency for Planning said a quarter of the region’s greenhouse gas emissions come from transportation.

The Chicago area is expected to gain about 2 million residents in the next 30 years, and if trends continue, experts predict a decline in the water level of Lake Michigan and more extreme storms and flooding, Elam said.

A “three-legged stool approach” is recommended to reduce emissions and stave off climate change by improving fuel-efficiency standards for cars, reducing the carbon content of fuels, and lowering the number of miles people travel in their vehicles, he said.

The agency is developing a comprehensive regional plan called Go to 2040. Among its goals are improving public transportation to reduce congestion and creating and preserving open space.

Roger Bannerman of the Wisconsin Department of Natural Resources discussed his research about the effects of road runoff on the health of waterways.

As road salt and other pollutants run off road surfaces into streams and rivers, fish species decline and bodies of water become less healthy, Bannerman said.

To address the issue, he recommended measures such as using alternatives to salt to remove ice from roads and building roads that are more permeable for water.

The city of Warrenville recently has experimented with building a road that reduces runoff.

Mayor David Brummel spoke at the summit about the city’s experience using permeable pavers instead of traditional concrete or asphalt in rebuilding a one-mile stretch of Warrenville Road.

The $4.7 million project is expected to be finished this fall, Brummel said.

The new road is being constructed on a gravel base with small gaps between the brick pavers. As water drains through the gaps in the road surface, the gravel filters out contaminants before the water soaks into the ground.

While the road is more expensive than a traditional surface, it reduces the possibility of flooding and prevents the “freeze-thaw cycle” that causes potholes, Brummel said.

The city has already had many visitors from other communities that are considering building similar roads, he said.

“There’s always a hope that there are ramifications beyond your own project,” he said.

Officials from the Regional Transportation Authority and the Illinois Tollway also attended the summit to discuss environmental initiatives their agencies are undertaking.

The event was sponsored by DuPage County, Benedictine University, The Conservation Foundation, The DuPage Community Foundation, SCARCE and the University of Illinois Extension.