It is claimed in some quarters - recently for example in Network Rail's Draft Route Utilisation Strategy (RUS) for Sussex - that using double deck trains would increase station dwell times and therefore reduce line capacity.

Less contentiously, they also say that many railway lines in Great Britain, built to a tighter loading gauge than those on continental Europe, would be too expensive to modify for double deck trains. Enlarging bridges and tunnels would be just uneconomic.

Do double deck (bi-level) trains increase station stop times? I was in Switzerland recently and timed a few at three stations in the Zurich area. This was totally unscientific: it was just that I was there, was able to do it and did it. I made no attempt to count passengers on and off: clearly this would impact on station stop time. Equally, it was mid-morning and not during the peak.

I timed a number of double-deck S-Bahn (suburban) trains, two double-deck InterCity trains and a few single deck InterCity trains: the stations were the low level (suburban) platforms at Zurich Hbf, Oerlikon Main station and Zurich Airport.

Of the double deck suburban trains, 2 had a station stop time of less than 30 seconds, 1 between 30 and 60 seconds, 2 less than 1 minute 30 seconds and one more than 2 minutes.
The two double-deck InterCity trains both stopped at the airport station for more than 2 minutes. One of the single deck ones stopped for between 1.5 and 2 minutes, one for just over 3 minutes and one for just over 4.
There were no single deck suburban trains.

It should be noted that the double-deck suburban trains were - to my eyes - by no means ideal for the purpose. In particular, when the Door Open button is pressed the bottom step deploys and only then do the doors open. Nominally this happens when the train has come to a stand, but in practice the doors start to open several seconds before! Similarly before the train re-starts, the doors close and then the bottom step is retracted (it actually folds up to lie more or less flush with the doors).

An alternative to double-deck trains is longer trains. This might not be a solution - and would also necessitate investment in infrastructure (ok, less than would be needed for double deck train clearances) and rolling stock.

Why isn't it a solution? The problem is that at so many London termini, the exits are at the front of the train. So that's where everyone wants to go, for a speedy getaway!

Some years ago I recall an ironic comment after one line was equipped - at some cost - with 10-car trains and 10-car platforms. The comment was to the effect that the solution wasn't trains with 10 coaches - it was trains with 10 front coaches! I also recall a survey done after the Clapham Junction accident where a morning peak train into Waterloo had more passengers than seats - but over 200 empty seats!

From my observations, I am not convinced that double-deck trains generally have longer station stop times than single deck trains.

Does anyone know of a more scientific survey of stopping times of double- and single-deck commuter trains, please?

In May 2008, the Stockholm Environment Institute (SEI) published a discussion paper, "Carbon offsetting and air travel - Part 1: CO2 emissions".

This discusses a number of systems whereby people can evaluate the amount of CO2 their flights are responsible for. It draws attention to the shortcomings of some of them: this revised paper includes some of the discussion by the organisations responsible for the calculators.

If you look at all of the calculators for the same flight, you can get quite a wide range of figures! The discussion highlights why this might be, and may motivate something better.

The paper, and part 2 dealing with non-CO2 emissions, can be found on the SEI's website. Visit the Stockholm Environment Institute website. It is also available to IARO members in the IARO library.