With the extension of the Merseyrail 3rd rail system in mind, hoping that I do not horrify the conservationists, how about reopening the West Kirby to Hooton line?
Well speaking as someone who admittedly probably knows more about the Wirral Peninsula than about the railways, this would be very difficult now I would think. At West Kirby, the "West Kirby Concourse" leisure complex (Swimming baths and library) was built over the ex-railway land specifically where this line would have ran out of station. Looking at old aerial photos of the Wirral, it appears to me that a bridge which used to cross the A540 carrying this line has also been removed, although I never saw it in person - it was before my time. I just can't see there's any room for this line to get out of the station now without some serious demolition.
In both Heswall and Neston, entire streets of semi-detached houses have been built over where the line used to run. (Davenport Road & Station Road respectively).
At least two further rail bridges have been removed that I know of in Neston. (One of which has been replaced with a narrow cyclist/pedestrian bridge).
The business case is also very weak. Despite the loss of this line, three of the towns on this route, Neston, West Kirby & Hooton are still connected to the rail network via the Wirral Line or Borderlands line. All still enjoying (admittedly indirect) connections to Liverpool, Chester & Manchester. Even Heswall (at a stretch) still is connected (via the out of the way station on the Borderlands line).
All of these places plus the smaller villages which lost their rail connection entirely (namely Willaston, Thurstaston & Caldy) are all connected to Liverpool and/or Chester via reasonably good bus services.
Add to that the fact the Thurstaston station was always a mile out from civilization anyway. (Apparently due to original landowner's objections). Then there's not much of a case for it. Also most of the areas of the Wirral that this line ran through are relatively affluent with near 100% car ownership with very low dependency on public transport.
Finally hikers (myself included), cyclists, birdwatchers & dog walkers etc.. are all so happy to have this excellent 12-mile long "Wirral Way" available for exercising and getting some fresh air. It really is quite a pleasant walk with excellent views across the River Dee to Wales. I don't think it'd be very popular locally to convert it back to a railway now.
Don't get me wrong though, I'm usually a strong proponent for reversing the Beeching Axe (and associated closures of that general era) where feasible, and reinstating as much as the full network as possible again. However, this is one 12-mile stretch where I just can't see it ever happening for the reasons above. (Really, I'd just love to be proved wrong though).
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As regards Bidston - Wrexham, I also have doubts to whether the passenger numbers would stack up. However, interest has been shown by several parties over the last few years, with various options being considered. A scheme was priced up by NR but came in as mega expensive so was not proceeded with. Certainly, I can see merit in opening some additional stations at the northern end of this line & extending the 3rd rail to the Woodchurch area. Going all the way to Wrexham would be more for operating convenience (eliminating the need for an isolated diesel service).
Indeed, there is the land there (an occasionally-used playing field) near the A552 primary road/M53 Junction 3 interchange for a park and ride station.
Not only that, but the site is right between the large Woodchurch estate and the Prenton suburb of Birkenhead.
These areas are currently only served by buses into Liverpool.
These happen to be the same buses I sometimes get on in Birkenhead going to work. Frequently they are full at peak times. Since, I'm only three stops from the tunnel, this is the reason why I get into work for 7:45 am and either leave at 4pm or 6pm (never 5pm!).
I think having an electrified station at the Woodchurch/Prenton site with a large car park would be a very good idea, perhaps even a bus interchange (or at least bus stop). I can see it as an area of potential growth for onward commuting via the Merseyrail network.
I'm not sure about the case for electrification from Merseyside further into North Wales though. I can see up to Shotton would be good initially giving access to the Deeside industrial estate from Merseyside. Likewise, the Wrexham end of the line is quite heavily used (particularly for short journeys from Gwersyllt into Wrexham), but how many people cross from Merseyside/Cheshire into Wales and vice-versa daily? It's a reasonably popular leisure/shopping route, but as for commuting I'm not so sure.
In my experience, most journeys on the Borderlands line seem to be short local journeys (e.g. Buckley-Shotton or Gwersyllt-Wrexham or Bidston-Neston etc..) rather than people traveling the entire length of the line. It's almost as if it's segmented around local communities.