After some discussion on this subject, what are people's views of what has been called variously the Varsity Line, the East-West Rail Link and the London North Orbital Railway? There have been several versions
Other than the rowing lake problem, and I'm sure it's possible to bridge a rowing lake, the lanes can run between the piers if necessary, the first version seems the easiest to do. Most of the route is still intact. Sending trains via Hitchin might save on new line, but puts extra pressure on the ECML section. The Bedford-Hitchin route is not necessarily as easy to build. Much of it is still there, but there are some missing sections. The Luton route either involves cutting through virgin countryside or rebuilding a line that has been built over in many places, not to mention trying to thread extra trains through the Welwyn Tunnels. The southern route would also involve a heavily-developed line, plus some sort of flyover at Watford, so that's also unlikely. Overall, I'd go for the first version, including the Stansted-Braintree-Whitham extension.
I reckon that there would be sufficient traffic to justify the line. Firstly, the North London Line is losing freight paths because of the increased passenger service. Perhaps there will be no freight paths during the day in a decade or two's time. Without a relief line, this means that Felixstowe and Tilbury will be entirely dependent on the Ely-Peterborough line. Passenger services act more as a cost-saving measure, to avoid the expensive in-and-out runs to London or time-consuming loops via Peterborough and Leicester.
- Oxford-Bletchley-Bedford-Sandy-Cambridge
- Oxford-Bletchley-Bedford-Sandy-Hitchin-Cambridge
- Oxford-Bletchley-Bedford-Hitchin-Cambridge
- Oxford-Bletchley-Bedford-Luton-Stevenage-Cambridge
- Oxford-Bletchley-Bedford-Luton-Welwyn-Cambridge
- Rickmansworth-Croxley Green-Watford Junction-St Alban's-Hatfield-Cambridge
Other than the rowing lake problem, and I'm sure it's possible to bridge a rowing lake, the lanes can run between the piers if necessary, the first version seems the easiest to do. Most of the route is still intact. Sending trains via Hitchin might save on new line, but puts extra pressure on the ECML section. The Bedford-Hitchin route is not necessarily as easy to build. Much of it is still there, but there are some missing sections. The Luton route either involves cutting through virgin countryside or rebuilding a line that has been built over in many places, not to mention trying to thread extra trains through the Welwyn Tunnels. The southern route would also involve a heavily-developed line, plus some sort of flyover at Watford, so that's also unlikely. Overall, I'd go for the first version, including the Stansted-Braintree-Whitham extension.
I reckon that there would be sufficient traffic to justify the line. Firstly, the North London Line is losing freight paths because of the increased passenger service. Perhaps there will be no freight paths during the day in a decade or two's time. Without a relief line, this means that Felixstowe and Tilbury will be entirely dependent on the Ely-Peterborough line. Passenger services act more as a cost-saving measure, to avoid the expensive in-and-out runs to London or time-consuming loops via Peterborough and Leicester.