It has been suggested that the old single track rail line between the City Line - just north of Fairwater station - to Cregiau be re-opened in order to serve new housing areas that might be built in the countryside between Cardiff & Llantrisant. It has also been suggested that this route continue NW from Cregiau to maybe Beddau or Talbot Green and then link with the mainline at Pontyclun - possibly into a restored bay platform. (Some planners thought that it could be a tram route which would continue as a street tram from Cardiff Central to Cardiff Bay - little realising that this would be impossible due to the fact that trams would not be able to operate on the national rail 25Kv network - plus the platforms on the City Line are unable to accommodate trams due to height).
It has also been suggested that a new Park & Ride be built on the northern side of M4 Junction 33 (Cardiff West) with people then being transported in buses via Culverhouse Cross, Ely & Canton to the city centre. Clearly this is a ridiculous idea due to the length of time it would take to reach the city centre. The P&R (plus associated business park at J33) would also cause delays at this strategic junction which surely needs flyovers /loops to produce a continuously flowing junction between the M4 & A4232. (It is also the main junction serving the whole of Barry as well as the rest of the Vale of Glamorgan including Cardiff Airport).
I am not sure that Network Rail would be too keen on re-building the Pontyclun to Beddau railway as it would involve a new level crossing over a busy 'A' road. Having said that, it would be possible to build a bridge. From Pontyclun to Cardiff Central takes around 13 minutes via the main line - far faster than any P&R from Junction 33 or a re-built Cregiau route could get people to the city centre.
The car parking situation at Pontyclun is a shambles with cars now strung out along the approach road and local streets. Clearly, Pontyclun is a very attractive railhead for the local population - especially as it has fast non-stop trains to Cardiff Central. I think that some additional parking could perhaps be provided on disused rail land to the NW of Pontyclun station and more could also be placed on the SW side. If the Beddau line is not re-built, then surely it would make sense to convert the track bed into a road to help provide better access to an extended car park at Pontyclun for people driving down from Llantrisant, Beddau & Church Village. (No signposts to Pontyclun station exist in the wider area such as near Matalan etc.).When the main line is electrified and a fast half hourly service is provided from Pontyclun - with modern electric trains (with plenty of capacity), then clearly passenger growth would likely increase dramatically from this station.
At the moment, few buses actually come from Beddau to meet with the trains at Pontyclun. (NAT provide a service that meets the occasional train). Other operators only go as far as Talbot Green. This lack of co-ordination is surely one of the reasons why so many people from this area rely on car transport to reach Cardiff?
It surely is in the best interests of everyone to encourage people to get to their nearest railhead for journeys further afield. Providing free parking at local stations is one way of doing this and would help alleviate overloaded highways at the approaches to cities.
PS. With electrification, I would think that a half hourly Maesteg (+ all stops between Bridgend & Cardiff Central) to Ebbw Vale would be the most logical service.