Merseyrail heavy rail rolling stock is in need of replacement. One approach is to replace gradually the existing heavy rail rolling stock with cheaper light rail rolling stock, similar to use on the London Docklands Light Railway. This would give more cars to a train, however in off-peak times only a few of these shorter, more economical to run cars need be used.
A great advantage is that smaller light rail cars can negotiate tighter curves than longer heavy rail train cars. This entails tighter curves when extending Merseyrail, like out of the Wapping and Waterloo tunnels.
On certain lines heavy rail dual power trains could remain, such as the proposed Wrexham to Liverpool Line when electrified.
Below: Docklands Light Railway train: