WALNUT CREEK -- The green trolley buses are about to get more green.

Thanks to a $4.3 million federal grant, the "Free Ride" will soon run on electrically charged batteries rather than by diesel power. It will make the downtown route the first in the county operated by all-electric powered buses.

The Central Contra Costa Transit Authority, commonly known as County Connection, secured the grant from the Federal Transit Administration's 2012 Clean Fuels Grant Program, which awarded $59.3 million to 27 projects throughout the country. With that money, the transit service will buy four electric trolley buses and two electric charging stations.

The electric trolleys will be used on Route 4, which starts at the Walnut Creek BART Station and then snakes its way around downtown to Broadway Plaza Shopping Center, and back to BART.

The amount of emissions to be eliminated, or possible electric-versus-diesel cost savings, are unknown at this point. That's why this pilot program is being done and is likely why County Connection got such a hefty grant, said Rick Ramacier, general manager of the agency.

"We can say for sure an all-electric-powered bus versus diesel will significantly reduce all emissions," he said.

But the energy used and emissions released to make the batteries to power the bus aren't known yet, because a vendor hasn't been selected and the project has not gone out to bid, Ramacier said.

While traditional

electric buses have meant electric wires overhead or on the ground, these buses will be powered by electrically charged batteries. There are no other busses in Contra Costa that run on this type of technology. The Valley Transit Authority and AC Transit both have electric demonstration projects, but those are for much larger full-route buses, Ramacier said. Route 4 is a good line for this trial because it's one of the most heavily used in the County Connection system, with 850 passengers a day, Ramacier said.

"The distance you can go is still relatively short, which lends itself nicely" to this type of electric battery service, he said.

Mayor Bob Simmons, who also sits on County Connection's board of directors, is thrilled.

"I'm very excited about this grant because it means the Free Ride Trolley will continue to serve the people who live, work and visit our downtown with quieter, cleaner vehicles that will make using the (bus) a more enjoyable experience for all," he said.The buses should be on the road in the next 12 to 18 months.

Contact Elisabeth Nardi at 925-952-2617. Follow her at Twitter.com/enardi10.