19 May 2011

IEP - A flawed concept

Details of the IEP project have been published in the June issue of Today's Railways. It does not look like a clever design.

The first point of criticism is that most of the units are hybrids and will be fitted with diesel engines, adding 16 tons to the weight of a 5-car unit, whilst being unused for most of the time, when they will be operating under the wires.

The second point of criticism is the length of the vehicles - 26 metres. Whilst this is a standard length on the Continent, it it too long for the UK, as the width then has to be reduced significantly to prevent excessive overhang on curves. Some work is being done on the infrastructure to reduce this overhang, but there must be better ways of spending the money. Passenger vehicles designed to run in the UK should not be more than 22 metres long so that they can be constructed to the full width of the available loading gauge.

With such long vehicles, to prevent having large gaps at stations with sharply curved platforms, the doorways have been moved well in from the vehicle ends, creating odd spaces which will be occupied by toilets, which is fine, and luggage space. That is not fine, because passengers cannot keep an eye on their property if it is far from where they are sitting, a situation which gives rise to anxiety every time the train stops at a station.

It is claimed that the stepping distance will be no worse than a mark 3 vehicle, but the stepping distances are one of the features of mark 3 stock where improvements are needed. In addition to being a hazard, awkward steps onto the train add to station dwell time as people have to be more careful when getting on and off.

Seating layouts are of course a matter for the operators to decide, but with rolling stock as expensive as the IEP, there is no alternative but to cram in as many seats as possible, which means that most of the seats are in an airline configuration. Although about one-third of passengers prefer this, and another third are indifferent, the problem with airline style seating is that it leads to a loss in the most desirable luggage space, between the seat backs where the owners can keep an eye on their things. Luggage space then has to be provided in special shelving, which also consumes seating space.

That the design has turned out like this it is no criticism of the engineers and designers involved. It is implicit in the concept of a hybrid train that can go everywhere without the need to change locomotives when it gets to the end of an electrified route. IEP is a good example of how a flawed concept has knock-on effects leading to a flawed design.


  1. This is getting increasing non-sensical - the original reason given for 26m carriages was that it gave more space per train length eg assuming a ~1m intercarriage gap and comparing to a standard 10 car 23m carriage train gives (23+1)*10/(26+1) = 9 (approximately) - ie a 9 car train instead of a 10 car train - giving an increase in usuable train length of (9*26)-(10*23) = 4 meter .. (or similar calculations of your own devising)

    Now they say they are to move the door inwards to maintain stepping distance (are they incapable of designing and manufacturing a fold out step? - the mind boggles) - I'd assume the end space becomes unavailable for seating - I really can't see how they are going to get an increase in capacity from this. (http://www.agilitytrains.co.uk/agilitytrains_superexpress.htm still claims 30% more seats !)

    My hope was that at least the electric version would be a good product - I really am doubting this now - initially I would have attributed flaws to the DfT's specifications, but now it looks like the hitachi's engineers are 'smoking crack' too (as the Americans say). It's difficult for me to see these design decisions, which are Hitachi's own choice, as anything other than folly.

    I would be interested to see an independant defense if someone thinks they've got the design right.

  2. A slide-out step is feature of most recent Swedish rolling stock such as the X31 and Regina series. End of problem.

    As regards width, running the relevant figures through a spreadsheet, reveals that there is an optimum length for passenger vehicles in the UK and it is certainly not 26 metres. There are also, surprisingly, a few extra centimetres of width available at floor level.