We hear this morning a Japanese bullet train is being tested on the London to Channel tunnel line. I awoke to a sales pitch on Radio 4 for these new faster trains, which we were assured were "safe" and "green". No challenge was offered to either of these propositions.

Faster trains use more energy for the same weight pulled than slower trains. They are only greener than modern cars if they run with good occupancy of the seats, and if the passengers find green ways to get to and from the stations.

No method of travel at speed is completely "safe". Train travel is relatively safe because they do not allow pedestrians or cyclists onto the tracks, because they only allow trains to run in one direction on any given main line, and because they do not run more than around 20 an hour on the track. Increasing either or both the speed and the weight of the train makes it more likely a rail will crack because that increases the force onto the rail, especially on bends where the pressure through the wheels is greatly increased. There will need to be a very vigorous inspection regime to avoid trouble, as damaged rails can create horrendous crashes.

The good news about importing Japanese trains is that they are lighter in weight. Part of the answer to the poor fuel consumption of our old trains on the network is to buy lighter weight modern trains from elsewhere that require less fuel to propel them. Buying slower lightweight trains would be better still, as it would allow us to run more trains per hour on the same piece of track. They would be both greener and safer than current trains and than the Shinkansen.

Greens should admit that all forms of engine driven travel burn fuel. The comparisons between some of the trains on our network and the motor car are not favourable to the train.