Worcester's problem is that the three main flows through it, London to Hereford, Birmingham to Hereford, and Birmingham to Bristol, form a triangle through the city area, which is not easily possible to handle by one central station, and furthermore the flows to both Hereford and Birmingham come from two different directions. Given the UK inability to arrange reversing services sensibly (or even at all), that just makes it too difficult. West Midland Trains operate Shrub Hill, but as I understand it have very little service there, this probably leading to the decision to have it unstaffed outside working hours.
Shrub Hill has roughly one train an hour to Birmingham for pretty much the entire day, although it's not entirely regular and some hours do have an extra train in between. It's my impression (though I haven't checked the actual figures) that Birmingham-Malvern/Hereford is the route with the most passengers. The reversal at Shrub Hill adds a minimum of 5 minutes or so to the journey time for the majority of the Worcester passengers. The absence of Rainbow Hill junction and the consequent two single lines arrangement through Foregate Street limits capacity, and they have recently found it necessary to install a down IBS at Fernhill Heath to halve the length of the section to Droitwich and so reduce the minimum interval between trains being able to come off the single line into that section. It's one of those all too common situations where it was very quick and easy to irrationalise the track layout back in 1973 and pare down the capacity, but putting it back how it used to be is considered so impossibly difficult people are afraid to even mention it.
Foregate Street station itself can get pretty heaving at times. It would in a sense be possible to run all the services Worcester has now from Foregate Street alone, but you'd be immediately running into problems of station as well as track capacity that at present we just about get away with.
Birmingham-Bristol doesn't really come into it because there aren't any. Services to/from the Bristol direction mostly reverse at Shrub Hill, Henwick, or Malvern Wells. And the service in that direction is pretty rotten and awkward; it has been for years and years, although it's a little bit better now than it used to be.
Once upon a time, though, things weren't like that. From I think the 1880s, the Midland made the Worcester loop the standard route for passenger services between Birmingham and Bristol, and just used the direct line for freight. And of course once upon a time we also had the services from the London direction heading north at Worcester implied by the very title of the OW&W.
All the Worcester lines were originally GWR lines, the Midland passing some miles to the east, although in irony the main road to Shrub Hill station, including passing the Worcestershire Sauce factory, is called Midland Road.
The Midland actually got here first, as the section of route in from Abbotswood Junction became usable before anything the GWR could make use of was completed. They had a goods depot alongside Midland Road, which runs parallel with the railway to the south of Shrub Hill, and when the dust finally settled over whether the OW&W was going to end up with the GWR or the Midland, the freight avoiding line round the back of Shrub Hill remained as a Midland/GWR joint section.
Midland Road was never the main road to Shrub Hill station. Originally that was Cromwell Street, which provided the impressive direct approach I mentioned in my previous post. It then became Shrub Hill Road, which comes in from the north-west up past Heenan & Froude. Midland Road was the road to the Midland goods depot (and Lea & Perrins), south of Shrub Hill. The old depot entrance is still very obviously an ex-railway bit of construction with setts in the road. These days Midland Road is quiet enough that you can usually cross it without having to wait for cars to pass at all, which makes quite a contrast with the roads outside the station entrance itself.
The industrial branches between Shrub Hill and the river were a feature of several magazine articles from times when Pannier Tanks served them, they crossed the local roads on the level, controlled not by normal crossing gates but just by GWR lower quadrant signals facing road traffic. One wonders how much notice road traffic took of them.
I recommend
http://www.miac.org.uk/ for lots of information about those branches and other aspects of the railways in the area (including the irrationalisation of Rainbow Hill Junction I mentioned earlier). Also
http://cfow.org.uk/ is worth digging through for old photos.
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