Montreal's transit corporation is switching to biodiesel fuel and buying hybrid buses in an attempt to green its fleet and cut carbon emissions.

All Société de transport de Montréal (STM) buses will run on biodiesel fuel by 2008, and the transition should be fairly inexpensive, said president Claude Trudel.

Bus engines can run on biodiesel fuel without requiring any modifications, and the cost of a fill-up should be the same. The STM even stands to save money on maintenance, because biodiesel is "a cleanser, so it will keep your engines and your cylinders cleaner," said spokesman Luc Tremblay.