Currently Elstree & Borehamwood is served by Thameslink which extremely unreliable by random cancellations and breakdown of trains.

The town is currently growing and will have an extra 2400 homes in the next 10 years = extra 7000 + people = extra 3000 + cars. The crrent transport infrastructure cannot take this many cars and people. By 2020 population of Elstree and Borehamwood will be nearly 50,000.

Several options coud be considered:

1.  Extend the Jubilee Line from Stanmore to Elstree

2. Extend the Northern Line from  High Barnet Branch to Borehamwood

3. Extend the Northern Line from Mill Hill East to Borehamwood

4. Remove thameslink altogether and add it to the London Overground Line with occasional  Thameslink services

Past Ideas: 

http://en.wikipedia.org/wiki/Elstree_South_tube_station

http://www.1900s.org.uk/1940s50s-edgware-tube-trains.htm