Without wishing to deviate from the aviation theme of PPrune......
The railway line between London and Cambridge is at maximum capacity south of Broxbourne. It has to accommodate
1. Stansted Express trains.
2. Fast service to Cambridge
3. Slow service to Cambridge
4. Services to Hertford East
5. Slow services to Broxbourne.
The only way that this will be resolved is to “four track” the line from Broxbourne to Liverpool Street. I am sure that if this was seriously considered the people who’s houses would have to be demolished to accommodate the additional tracks would be setting up a campaign all of their own. Nice try but there is more chance of linking Stansted airport to Braintree by rail than four tracking this section.