(AP) — A Lincoln transit system official says a third of its bus and minivan fleet will be running on compressed natural gas within two years.

StarTran manager Mike Davis said five new buses that run on compressed natural gas should arrive and be in service by early August.

StarTran plans to buy eight more compressed natural gas buses and 11 compressed natural gas vans as replacement vehicles. Eventually, a third of its 75 vehicles will fuel up on compressed natural gas.

Brandy Johnson of Black Hills Energy says greenhouse gas emissions from compressed natural gas buses are 20 percent to 30 percent cleaner than the most efficient diesel bus.