Crossrail is now running about three years late. Several layers of bad decisions have led to this.
Crossrail was originally conceived as an east-west relief route for the Metropolitan and Central Lines. A quick and easy fix would have been a new tube line on roughly the same alignment. This could have used small bore tunnels and been self-contained, with self-driving trains as currently operating successfully on other tube lines. Being a self-contained route without junctions, the line would have been optimally reliable, with a service of 34 trains an hour being achievable, as on the Victoria Line. It might have been extended to Heathrow, or it might have run to Hammersmith over part of the present Metropolitan Line. It might have joined end-on to the Jubilee Line at Stratford, avoiding two sets of reversals. Such a line would have been running at least five years ago.
As it was, there was mission creep. Large bore tunnels were used, with full size trains and overhead electrification, the trains had to be designed to accommodate three different systems of signalling, and the route is shared with the main lines, which builds-in unreliability and potential widespread disruption.
Having got to that point, however, risk could have been reduced by putting in a conventional signalling system on he tunnel section, which is the current obstacle to getting the service running.
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