Speaking to TOI, chief engineer S.M. Borse said that PMPML buses have to maintain a norm and keep their emissions below 65 Hartridge Smoke Unit (HSU is the basic unit for auto emission. Diesel-driven vehicles must not exceed 65 HSU).

He pointed out that the engine overhauling of old buses is undertaken by PMPML workers themselves. However, it was found that this did not bring about the desired quality in engines and the plan now is to get engine rehauling done by the bus company itself. "This will help maintain the quality of engine and indirectly reduce pollution," Borse said. The PMPML has also last year undertaken a pilot project to run buses on a combination of biodiesel and diesel.

While the experiments were conducted on 100 buses, it was determined that the combination of 20 per cent biodiesel and 80 per cent diesel gave the best results, with respect to pollution by reducing exhaust emissions of carbon monoxide, sulphur dioxide, particulate matter and unburned hydrocarbons.

However, since the prices of bio-diesel shot up, the idea of converting the entire fleet into diesel and bio-diesel was scrapped by the PMPML.