Croxley Rail Link
The Croxley Rail link was a proposed rail link between the Metropolitan Line at Croxley and the West Coast Main Line at Watford Junction. It would have taken over the former British Rail Croxley Green Branch. The Croxley Green Branch was closed in 1996 due to low passenger usage because of the British Rail Closure by Stealth on the Branch in addition a new road bridge severed the link just before Croxley Green.
Tube
The original proposal was that it would be an extension of the Metropolitan Line. This would see the existing Metropolitan Line station at Watford close as all services would be divert via the Croxley Rail Link to Watford High Street ware they would join the Watford DC Line to Watford Junction. To allow passengers to connect to Avanti West Coast, Southern Rail and London Northwestern Railway services. The proposed frequncey was 8 trains per hour of Metropolitan Line services from London with an additional 2 trains per hour from Chiltern Railways.
Tram
Some more recent proposals have been to make it a tram link to save money as the funding of the Croxley Rail Link is proving to be a challenge with first being considered well over a decade ago.