I shall certainly look into that. It is a responsibility of my right hon. Friend the Chancellor of the Exchequer. I know that my hon. Friend has first-hand knowledge of this subject. I am sure that my right hon.

Friend the Chancellor will be interested in his experience, and I will ensure that these comments are drawn to his attention.

Compressed natural gas has to be stored at very much higher pressures—up to 3,000 psi—and compressed to very high pressure to store reasonable quantities in the vehicle. This requires much stricter standards for safe storage and use. That is why the number of vehicles using CNG is very small, and the number of special approvals that we have given is also very small. If the demand for the use of CNG were to increase, we would have to consider an amendment to the Road Vehicles (Construction and Use) Regulations, setting out standard specifications for the gas systems to be used.

We permit reputable organisations to experiment with CNG in road vehicles, but they must apply to the Department of Transport for approval, with details or the gas system that they propose to use, its design specifications and how they propose to inspect and test it. At present, to my knowledge, three organisations hold such approvals, with 29 vehicles running on the roads. In the past, some have experimented with gas reclaimed from waste disposal areas, but all are now obtaining their supplies from the gas mains.

British Gas plc recently said that it wishes to promote the use of CNG in road vehicles, and it is setting up an organisation for that purpose. As my hon. Friend said, it is currently setting up field trials in the United Kingdom which will make use of experience in the Netherlands and Canada—the latter arising out of the recent acquisition of Consumers Gas. A great deal of work will need to be done before any results become apparent, but my officials are working in collaboration with British Gas to formulate suitable specifications for the gas system for inclusion in the regulations. Early developments in this market are likely to be in relation to commercial vehicle fleets having the relevant characteristics, and that is where the important environmental benefits will be most evident. I must stress, however, that it will be a long time before vehicles running on CNG are commonly available for the private motorist.

Natural gas has advantages, in that it is abundant and its CO₂ emissions can be about 30 per cent. lower than those of petroleum fuels. However, natural gas, or methane, is itself a greenhouse gas, and must be compressed or—in what are at present rare cases—liquefied when used in vehicles. One survey taking possible methane losses and compression and liquefaction into account puts the relative greenhouse emissions of natural gas used in vehicles at 19 per cent. lower for CNG and 15 per cent. lower for liquefied gas, compared with those in vehicles using conventional fuel.

But that advantage is largely offset if account is taken of performance and space standards. That stems partly from the weight and space penalties associated with storage of CNG in the vehicle, and the likelihood that any transition to CNG vehicles would involve dual fuelling, so that cars use petrol or CNG.