San Diego Metropolitan Transit Development Board has selected 117 buses equipped with the Cummins Westport C Gas Plus engines that its low- emissions C Gas Plus engine with the right to increase the order to 357 if certain options are exercised.

The 8.3-litre natural gas engine will be installed in 35 to 40- foot transit buses scheduled to go into service with San Diego Transit Corp. (SDTC) from early 2003.

While the bus manufacturer has not yet been selected, the C Gas Plus was the only low-emissions engine to meet the performance standards set. The 280-horsepower engine is intended mainly for buses and urban work trucks like refuse haulers and pickup and delivery trucks and was introduced by Cummins Westport in 2001.

Some of the new buses for San Diego will be used to retire older diesels while others will augment the 350-strong fleet. If all of the options are exercised, San Diego's fleet will grow to 744 by 2006 and will be 100% natural gas powered at that time.

In test results released by the California Air Resources Board (CARB) in August this year, emissions of oxides of nitrogen (NOx) from a bus powered by the C Gas Plus were claimed to be significantly below a diesel engine running on low sulphur diesel fuel and fitted with a particulate trap.