The organisation ran 21 of its 40,000 vehicles on one of these alternative fuels, each one paired off with petrol and diesel-only vehicles as controls. Mike Horlor, the Royal Mail's head of fleet, said: 'I'm convinced we will have LPG and possibly CNG vehicles and will know where we are going on this by early next year. We are moving away from the universal use of diesel because of the need to address the drive by local authorities to improve air quality. We want to take the initiative before we are forced to change.'
While the pump price of gas is cheaper than the price of diesel, Horlor said the maintenance costs of the bi-fuel vehicles were higher which impacted on their wholelife costs. A further discovery was that after market conversions could actually lead to worse emissions when using gas compared to petrol.
Peter Histon, fuels technology manager for BP Amoco, the LPG supplier during the trial, said: 'We discovered that care must be taken when selecting vehicle technologies. The best choice is the manufacturer option 'from new'. Our experience is that retrofit conversions of vehicles to gas can have the opposite effect and can actually make emissions worse.'