THE ENVIRONMENTAL IMPACT OF NATURAL GAS VEHICLES The natural gas vehicle (NGV) presents one of the few options to current automobile related environmental problems that is both feasible with today’s technology and commercially viable. NGV technology is not new, in fact natural gas preceded petrol as the preferred fuel for internal combustion engines and further approximately 1 million vehicles currently run on natural gas around the world. The primary reason for choosing natural gas as a fuel to date has been economic - in countries which have there own gas reserves, gas is cheaper than liquid fuels. There is also a significant advantage to the gas utilities in terms of optimising the utilisation of the natural gas network. The novelty is that NGVs are proving to be significantly cleaner than their liquid fuelled equivalents. Whilst these gains are in part very evident they are unfortunately inadequately recognised by the legislation that is intended to protect the environment. The gains for NGVs have been shown to be outside the official test cycles and measure and huge errors in predicted vehicle emissions have been shown to exist.