If SELNEC had been able to secure the funding for the Vic-Picc tunnel we might be having a very different conversation.
On the other hand, one only has to look at the Aire Valley lines, which were also slated for closure in the 80's, to see how a route could be transformed as a conventional railway.
Comparing apples and pears. Manchester-Oldham is about the same distance in miles as Shipley-Leeds. From Keighley or Skipton it's very definitely not an inner-urban system.
But look at Leeds' traffic to see how it's crying out for a light rail system.
LO is good in parts, but in other parts less so. The Watford DC lines service is actually pretty poor at 3tph, far worse than any of the Metrolink lines.
Inner-urban lines are often better suited as light rail. Compare the old West Croydon-Wimbledon train to the Tramlink. It's night and day.
Fact is the Oldham Loop train service was *dire* and several stations were very inconveniently sited. Mumps was a long- and intimidating at night- walk from the town centre. Metrolink blows it out of the water.
Not every line is suitable for conversion to light rail, but Oldham and Bury have got a much better service than they had with heavy rail.