To some extent comes back to no one has built a regional train since the 158s over 30 years ago, tend to have express trains or commuter trains and nothing between.
Agreed, we haven't had any new regional (express) trains for ages, apart from the class 175s (and there aren't many of them - although they are available). Assuming we are talking for non-electrified routes here - there has also been the class 444s for electrified routes which as far as the train is concerned is a reasonable regional design (interior fit out is changeable - bodyshells are not).
For clarity my idea of a regional train is a 100mph (maybe 110mph on 25kv), with seats suitable for 3+ hour journeys, doors suitable for churn, and some commuter work, about 5 or 6 cars long and multi-mode traction
I'm not sure why you include 'doors suitable for churn' - if you do that surely 158s wouldn't count and 170s/168s would. My specification for an ideal regional express train would be:
- multi-mode traction (a pantograph, or provision for one to be easily retro-fitted, should be mandatory for all new rolling stock, not just regional express)
- unit-end gangways (not relevant to regional express vs suburban, hence I consider the 175s to be a regional express design, but very much prefrable)
- low track damage (ability to use Sprinter differential linespeeds) and low running costs (fuel economy etc.) to help the economics of rural lines (as above, the class 175s don't meet this requirement but are still a better choice than 170s for the buiser regional express routes like Cardiff-Nottingham and Manchester-Swansea)
- top speed of at least 90mph, probably 100mph (could be higher, but must consider the above two points - I think I've seen 115mph suggested as the limit for end-gangways)
- flush-closing (ie. plug) exterior doors
- sufficient toilets to meet the rail delivery group best-practice for inter-urban services (85 seats per toilet if I recall correctly) - this is likely to mean one toilet per carriage
- generous seat pitch (spacing between rows) - I think on the class 175s this figure is 84cm for the airline-style seats and would be my starting point*
- roughly 50% of seats to be grouped in bays of four around tables, and these to be perfectly aligned with the windows to avoid even partial view-blocking
- internal doors between vestibles and passenger saloons (and between passenger saloons and gangway connections, if applicable), to prevent draughts when the exterior doors are open (and cut noise from gangways)
- toilets should be accessed from the vestibles and not the passenger saloons (so you always need to walk through two doors to go from toilet to seat or vice-versa)
- a reasonable provision of luggage racks
- large windows, both horrizonally (to ensure the tables can be aligned with them without compressing seat pitch) and vertically (Pendolino-style narrow-slits need not apply)
- seats suitable for 3+ hour journeys* (not even InterCity stock is getting these at the moment, we seriously need a new design of seat that will appeal to car users who have been away from rail for a while and have not had their expectations managed downwards at each refurbishment / fleet renewal)
- 2+2 seating
- a high-quality door mechanisim that opens and closes as rapidly as possible, to limit the impact on dwell times
- reasonable acceleration at low speeds, recognising that some regional express routes have lots of closely-spaced request stops on part of the route
- a recognition that the comfort (and luggage) requirements above, plus the fact that passengers should not be expected to have to stand on such services,** mean that the design should provide the maximum possible furnishable space - thus vestibles (and therefore exterior doors****) should be as narrow as possible (or reduced in number) while still allowing wheelchair access etc. and crumple zones for high-speed operation should be avoided
Really, this is the same as an InterCity train but with fewer coaches (so no buffet, due to having fewer passengers to provide custom), no first class and a reduced top speed to improve acceleration (gear ratios), reduce running costs and allow end-gangways.
* the overall design needs to be tested with some sort of mock-up BEFORE any contracts for the actual fleet are signed, to allow changes if the initial supplier is not up to scratch
** regional express services make fewer stops on the more-congested parts of the network (in big cities) where passsenger numbers are highest (meaning a high number of passengers will be making journeys of well over 20 minutes***, compared to a much small number of passengers doing five minute hops between rural request stops)
*** I believe this is (or was) used as a PIXC definition for SWT services out of London Waterloo - for services that were not scheduled to stop within 20 minutes after departing Waterloo the definition of 'capacity' was equal to the seating capacity of the train - ie. ANY passengers standing on such a service would have seen the TOC penalised
**** this is the
opposite of the wide doors that tend to be recommended for dealing with 'passenger churn'
