How much spare capacity is there under the river? The idea of all Merseyrail trains arriving in liverpool on its underground network seems attractive, but it is surely way beyond the scope of the original Mersey railway for outer suburban traffic and even inter-regional (Wrexham - Liverpool) trains to all go through the tunnel. So interchange has to be the only alternative. Having said that if the local north Wirral suburbs have sufficient demand should a new interchange be considered towards Neston and a 3rd rail Merseyrail service from there, possibly coupling up at Bidston to conserve train paths?