The editorial ‘Emissions “out of control”’ (December 14) highlights an important environmental problem but meanders when it comes to discussing remedies.

Improving the country’s road network is not at all likely to bring transport emissions under control, if anything, quite the contrary as car numbers will soon take up the ‘slack’ created by the improvements. The effect, known as traffic induction, has been observed and well-documented for at least 50 years.

Restricting car numbers is a move in the right direction but simply taking off the road the worst polluters and restricting the importation of second-hand cars with high emission levels is not enough. We need to have fewer cars of every type on our roads if we really want to cut down on transport CO2 and other transport GHG emissions, not to mention other pollutants of more direct relevance to human health like fine particulates from diesel and ozone derived from both diesel and petrol emissions.

Two instant reactions to the European Commission’s report gave cause for concern.

The first, by Noel Aquilina, of the University’s Department of Physics, said gasoline engines are major sources of nitrogen oxides and diesel engines of carbon monoxide (CO). I believe the situation is the opposite, with diesel engines giving off less CO2 than gasoline per kilometre.

Then, Ray Ellul poured scorn on the idea that electric (battery) cars would cut down on transport emissions. The battery charge would have to be obtained from the power stations, so the emissions of CO2 would be merely transferred from tailpipes to power station chimneys.

There are many comparisons of the amounts of CO2/km emitted by diesel, petrol and electric cars. Of course, CO2/km emitted by the last depends on the type and efficiency of the electricity supply. But even with coal-fired or HFO power stations, battery electrics (BEV) come out slightly lower than petrol and on a par with diesel.

With a natural gas-powered supply as we now have, BEV produce less than half of IC CO2 and, moreover, this changes very little with age of car. In fact, a shift to BEVs is quite worthwhile for CO2 cut-back in our case.

Ellul went for fuel cell cars, on grounds that hydrogen “combustion” in a fuel cell will generate electricity to drive a motor, with the only end product being water. The problem here is to obtain hydrogen in the first place by a method that does not generate any CO2. Using renewable energy would be CO2 free but then one could use such sources to charge BEV batteries directly.