I have searched the forums for dedicated thread but not found one.
There is a good article in the current edition of RAIL which got me thinking. When I lived in Glasgow I often travelled to Paisley from Milngavie. The journey was relatively long due to changing at Partick and the Central.
I really don't get the resistance to a common sense scheme. (I know TS are difficult to deal with)
You didn't always need to change at Patrick and Central. At least half of the trains from Milngavie go through Central LL. A change at Patrick can be exceptionally quick - IIRC it's a 6 minute connection on your outbound journey when you're on the train going via GLQ?
I have gone on record on the forum as being opposed to the scheme, and I have yet to be persuaded otherwise. It's a scheme that gets a lot of support because lots of the infrastructure is in place, but I don't think it solves any of the problems that it claims it can solve - it generally puts the problems elsewhere.
First of all, it completely bypasses the city centre. Relatively few people want to go to Glasgow Cross or The Gorbals. People want to go to Glasgow Central and Queen Street. If you divert people away from the city centre, they probably won't take the train.
So the solution to this is the chord at High Street station, allowing Crossrail trains to run to GLQ. I'm no expert on the infrastructure works required, but it looks like you have to create a line that turns the train about 140 degrees in the space of about 100m. It also has quite a steep incline going towards High Street. That seems painfully slow and expensive, and I suspect you'd need to move High Street station further to the West (i.e., into the tunnel under High Street itself) which would prove very expensive and disruptive. And I don't think that whoever owns the public car park that's in the way will shut down business without a substantial pay off. Even if you did this, the journey time is going to be considerably slower than the equivalent into Central. You'll take commuters away from a mainline station (in some cases, like Paisley Canal services, they'll even be able to see Central) and onto a ten minute detour through the East End before dumping them into the bowels of Queen Street.
Next, you have the capacity on the North Clyde Line. It's already at 8tph through Queen Street. Yes, there is capacity there, but there's no capacity further West through Patrick which is very close to its capacity at the moment, with few (if any) options to improve the situation. The Kelvinhaugh turn back is an option, but it eliminates the benefits of direct services to Patrick and the North West and it reduces capacity on the line through Charing Cross, limiting the number of trains that could make use of Crossrail. Looking at your journey, Paisley-Milngavie simply won't happen.
What trains would you divert? If we assume a ten minute addition to journey time (which I think is reasonable), no-one will want this for their own line. Commuters will be peeved if their service is chosen to take longer in order to create capacity. There's suggestions for alternative services, for example 2tph EK-GLC and 2tph EK-GLQ-somewhere, but that's not a great option for commuters who won't know which station to use - and unlike the North West of the city there's no "Patrick" where you can easily change (West Street is mooted, but it relies on all the trains going to Crossrail being Ayrshire trains. I think these trains will simply empty at West Street and run through to GLQ essentially empty, as it will likely be quicker to transfer than to stay on the train if your destination is the city centre).
And another question that's never quite been answered - what are we creating capacity for? The only thing that's likely at the moment seems to be an extra 2tph to EK which I would suggest could be achieved in a much more cost effective way. I have no doubt that more capacity will be needed in the future, but you have to have a coherent plan and I don't think this is it. Diverting at most 4tph (and that is the most you will achieve) to Queen Street Low Level is a short term solution, and I remain to be convinced that it's needed. I would argue that 4tph to EK could fit into GLC high level as it stands, and diverting the Lanark trains back to the low level could create another two slots. No infrastructure required.
Another option that's mooted is the possibility of Edinburgh-Ayrshire direct via Bathgate, Airdrie and the new Crossrail. Sounds very good, but the end-end journey times won't be competitive. This is one of the slower routes between the two cities. And given that the existing service is between 2-6tph into Glasgow, the reality is that to facilitate the new service two trains will be diverted away from the city centre and out to Paisley. What do you divert? The express service becomes less competitive if you're not going to the city centre. The all stops is too slow for end-end journeys and deprives passengers of a journey opportunity to Glasgow City Centre. And the Airdrie terminator would half capacity at the intermediate stations. And the same argument can be had for whatever Ayrshire/Inverclyde services are chosen to bypass Glasgow. There's also talk of this being used as GARL - again, why waste money taking airline passengers away from the city centre? That's where incoming traffic wants to go!
Crossrail is inherently flawed. It will cause significant disruption during construction. Most people will not want their trains to go over this route, as it will be longer and take them away from where they want to go. It will not create significant additional capacity at Central, and will instead cause capacity problems through Queen Street Low Level.
Yes, there are problems in Glasgow's rail network, not least that trains from the South and trains from the North arrive at two unconnected termini. However, Crossrail (despite being promoted as "the missing link") does not solve this or indeed any other problem. The only reason I can see why it's frequently cited as "The Answer" is because lots of the infrastructure is in place already.
I think to overcome the problems, we need to think a lot bigger. Think more along the lines of London Crossrail. I would suggest a new line from Paisley to Renfrew (giving that town a station), South Glasgow University Hospital (Bus connections aplenty and a major employment centre), Govan (for the Subway and more buses), Buchanan Street (new underground station, offering connections to Queen Street, Central and the Subway -provides an underground travelator link between the two existing stations), and out to Cowlairs to integrate into the North Glasgow commuter lines. This would largely be in tunnels, of course (Exact route is open to revision!). This would be exceptionally ambitious and very costly, but it would provide a real solution. It would create capacity in Glasgow Central, as you can divert lots of Ayrshire and Inverclyde trains this way (and run a GARL through this corridor too). It would create capacity at Queen Street as well, by diverting (say) Cumbernauld services and Stirling locals through the new tunnels. It would not impact on capacity on existing lines. It would link Paisley to the West End by linking into the Subway at Govan. It would give Renfrew a heavy rail station. I'd rather that a proposal like this (better thought out, of course) would be a better use of public money than a short term stop-gap like the proposed Glasgow Crossrail.