I was involved in a feasibility study into shared use of Wednesbury to Brierley Hill by tram-trains and NE-SW freight trains on a reopened route between Walsall and Stoubridge in 1997. And again in 2008. At some point in between a scheme was drawn up for a single track freight line alongside a (mostly) double track Metro route. None of these has attracted enough funding to go ahead.
One of the main reasons why Centro and Network Rail were so keen to reopen the South Staffs line to freight traffic is that it (along with the Sutton Park Line) would free up capacity on the Camp Hill line to allow a passenger service to be re-introduced between King's Norton and Birmingham Moor Street. But last I heard is that Centro have practically given up on this project because they've sold the land on which the Bordesley cord was to be built. So therefore I can't now see any reason why they shouldn't just go ahead and build a standard double track Metro line on the old British Rail alignment between Wednesbury and Dudley with street running onwards to Brierley Hill.
Centro have recently announced that they're conducting a study into the possibility of using the Metro as a way of improving the connectability of the Birmingham city centre HS2 station. A draft map I found on the BBC News website shows no fewer than 3 new lines being considered alongside the smaller projects which are already listed on Centro's website as being in development.
These lines are:
Wednesbury to Brierley Hill.
Centenary Square to Hangley Road (terminates at a park and ride site next to junction 3 of the M5).
Adderley Street to Birmingham Airport (a loop line with two routes to the airport, one running along the Coventry Road, another via Chelmsley Wood.
There's no mention of new lines running to the Walsall area, something which Centro have had detailed plans for for about 10 years now. So no route from Birmingham City Centre to Walsall via Great Barr and no route from Wolverhampton to Wednesbury via Wednesfield, Willenhall, Walsall and Darlaston. I think we can now assume these plans have been scrapped.
But even for the lines they're still committed to, if they have business cases of over 1.5 and Centro insist they'll improve HS2 connectivity, then there's no reason why the government shouldn't commit funding and get all 3 lines built ready for when HS2 opens, if not before. If a big bang expansion has worked in Manchester, I can't see why the same success story can't be repeated in Birmingham.
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I'd also like to add that I think the Wednesbury to Brierley Hill lines should be built in two stages with the line being opened as far as Dudley town centre before construction starts on the extension to to Brierley Hill. Brierley Hill may have to wait two years longer to get it's Metro service, but the priority needs to be getting the Metro to the main population centre in a part of the conurbation which is currently very badly served by public transport.
And secondly, regardless of the business case for the major expansion projects I've mentioned, Centro need to revisit their plans for the Birmingham and Wolverhampton city centre extensions. They need to go back and resurrect the more ambitious plans for a Wolverhampton city loop tacking trams deeper into the city centre and then onto the bus and railway stations. Not only would it better serve the city centre but it would also not create a situation whereby there are two tram termini in Wolverhampton city centre, and all trams can run onto the railway station.
Secondly, the New Street to Centenary Square extension needs to run through to Five Ways, even if the Hagley Road extension to Junction 3 is never built. Extending it to the other end of Broad Street would allow it to better serve the Bridley Place and Five Ways business and entertainment areas. After all, that's why the Metro is being extended on to city streets in the first place, to take it to places where people actually want to go in the city centre instead of just terminating at Snow Hill.