Option one, called the 'Metro Option', would be a stand-alone Underground line with high-frequency services running from Wimbledon to Alexandra Palace. Central stops would include Clapham Junction, Victoria and Euston.
TfL said that this option would provide "valuable" crowding and congestion relief to the Victoria line and would help relieve Victoria, Waterloo and Liverpool Street rail stations.
Option two, the 'Regional Option', would operate in a similar way to the existing Crossrail route. It would follow the same route as the Metro option, but would be extended at both the northern and the southern ends of the route onto suburban rail lines.
TfL said that this option would remove some inner suburban trains from Waterloo and Liverpool Street by running them through a Crossrail 2 tunnel beneath central London.
"In addition to helping London's transport network keep pace with growth, Crossrail 2 would offer benefits to local residents and businesses by offering more direct, fast, frequent services that are not available at present. Passengers would have new travel choices to avoid crowded transport interchanges," said TfL in a statement.
Construction on the first phase of Crossrail, which will run from Maidenhead and Heathrow to Abbey Wood and Shenfield, started in 2009. Trains on the line are due to begin operating in 2018.
The Crossrail 2 consultation is open for responses until 2 August. TfL said it expected to report on the consultation to the Mayor of London later this year, following which the safeguarded route for the line could be updated. The application is expected to be submitted around 2018 – 2020.
