ERTMS will reduce headways so there’s no need to build new lines to create more capacity, is there?
On plain line, the specification for ERTMS would reduce headways, perhaps from 3 minutes to 2.5 minutes. But it is not clear at all that any meaningful improvement can be delivered at junctions, since critical section clearance times will not change. It is ultimately junctions that constrain route capacity. So a necessary concomitant to get the capacity benefit of ERTMS is probably to invest in disruptive and expensive junction improvement schemes. It is also only fair to point out that there is a long way to go to establish even these modest capacity benefits from ERTMS, for which the business case actually primarily rests on savings in maintenance costs once lineside signals and track circuits can be done away with.
