At present, trains from Hitchin to Cambridge have to cross three other lines to switch between the East Coast Main Line (ECML) and the line to Cambridge. This reduces capacity for other services and can lead to delays.

The new route will be a combination of embankment and viaduct, with the viaduct carrying the Cambridge line over the ECML. The length of the viaduct has increased as the plans have evolved in order to reduce the number of loads of fill required for embankment construction.