The entire aisle in a Mk3 is a bottleneck, getting on and getting off - it's only got room for one person to move along.
You complain about 1/3 2/3 doors - in fact, is there anything on British trains that isn't entirely wrong because you seem to have pretty much worked your way through everything on the rails here moaning about it - but these have wide vestibules and short aisles and load and unload a whole lot faster. If someone stops about three rows of seats into a Mk3 and starts putting up their bag/taking off their coat without taking any notice off all the people behind, that causes a bottleneck.
So Mk3 stepboards are too narrow - well at least they don't involve clambering up and down steps like so much of the rolling stock in Scandinavia and other places across Europe. Not exactly the height of design perfection and a first-rate bottleneck, I would say.
As for the position of the toilets, have you forgotten where they are going on 26m IEP coaches that you have previously told us are another example of terrible British train design? That's right, in the end corners, beyond the doors.
My criticism of British train design seems to be making you angry for some reason. British trains were at one time the best in Europe. Compare BR mark 1s or pre-nationalisation stock with contemporary stock anywhere else in Europe.
Modern European trains have retractable steps, platform-gap bridges, low floor centre sections, all sorts of devices and features to make them accessible. The issue on continental railways is the variety of station platform heights which have to be catered for.
Not every feature of the IEP is terrible. At £2.7 million a vehicle, there ought to be something right about them. They are just incredibly bad value for money. But putting the luggage in that part of a vehicle is a bad idea unless the intention is to provide secure lockers. As for their station dwell time performance, we shall see. The doors had to be located away from the extreme outer ends to avoid excessive stepping distances at convex platform faces. They are described as being "no worse than mark 3".
My point about the relative loading performance of the two types of vehicle configuration is that there are no types of stock where all the other characteristics are the same. An all-other-things-being equal judgement can not be made, which would separate out the effect of the one factor. It is just bad science to come an any conclusion at all, yet whole fleets of stock eg the 395 have been designed on the assumption that moving the doorways away from the ends is in itself going to shorten station dwell times.
With a single file of people at each doorway, the bottleneck on mark 3 stock is likely to be - and in the absence of solid research I would put it no stronger than that - the speed at which people can get on and off the train. Clapham Junction, East Croydon and Brighton have curved platforms which gives rise to wide gaps at convex faces. The stepboards on the class 442 stock are narrow, the only handholds are the pillars for the swing-plug doors, which are of large diameter and difficult to get hold of. So people are cautious when boarding and alighting from the train, which takes time.
Passengers on the Brighton line tend not to have much luggage unless they are travelling to or from Gatwick. On inter-city routes, when people are putting luggage on or taking it off the shelves, they will cause an obstruction. The length of the aisles makes no difference to dwell time as people are moving along inside the vehicle at the rate that people can get off the train or past the people dealing with their luggage. Thus in this situation, that is likely to be - again I will put in no more strongly than that - the pinch point.
The most recent generations of 1/3:2/3 stock eg classes 376/378 have wider doorways than earlier types and standback space as well, enabling people to go through the doorways two abreast or to pass each other with one boarding and one alighting. That will definitely speed things up at stations but at the cost of seating capacity.
If you watch people getting off class 375/377, they tend to go through in single file even though the doorways are wide enough for two (assuming the train is not so crowded that people are standing in the vestibule and causing a blockage). On unrebuilt classes 313 etc, people almost never went through the doorways two abreast.
The effects of having wide doorways at the ends, and unobstructed access to the saloons are speculation because such trains do not exist. Someone ought to find out by building a realistic mock-up and carrying out realistic loading and unloading tests. When several billions are being invested, the cost is peanuts and the information valuable. That is the sort of thing the Railway Technical Centre used to do but alas they are no more.
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But it could require the adaptation of every single vehicle to make them DDA compliant...
What adaptations would those be? The big expensive one is wheelchair accessibility, is it not? The rest covers things like the colours of push buttons and the force required to operate them.
