A suggestion from Paris
As the London tube system will only get more complicated, maybe it is time to consider using an idea from the Paris Metro: make more of names of the terminii of each line. I think that one of the biggest problems for new users of the system is the use of compass-point directions (‘Eastbound and Westbound’) at tube stations.
Sometimes I need to change at Westminster. When I do, I see that the Jubilee platforms are labelled as being for trains going ‘Westbound’ and ‘Eastbound’. Surely from the point of view of most Londoners, certainly for those who navigate by the tube map, the Jubilee line goes north-south at that point, and the sub-surface lines east-west. The District and Circle aren’t marked as going Northbound and Southbound at Westminster (which are the directions it travels at that station).
Both the Jubilee and Bakerloo lines leave Baker Street to the east. Their platforms aren’t described as Eastbound.
Signage could look like this:
With a revised (2012) tube map looking like this:
Click to enlarge.
alex4D old blog 
No thank you! As an only occasional visitor to Paris, I find it confusing. With time I’m sure I’d learn the names of the termini. But “fresh from the colonies” in London, I found the concept of eastbound on the tube incredibly intuitive. Why change what ain’t broke? With so many lines branching at the extremes, that’s an awful lot of termini to learn. How about “Piccadilly westbound – for Heathrow or Uxbridge”. Wait: don’t a lot of signs already state that?
Something needs to be done. East-West is naturally confusing for people, especially when making a decision under pressure. It caught me out myself the other day. And, somewhere like Liverpool Street, with Circle Line westbound and H&C eastbound from the same platform is just nasty. I’ve never liked the way that the Piccadilly Line starts off eastbound, but then changes its mind and ends up being northbound either.
People with excellent knowledge of London are less likely to make mistakes, but what about tourists?
Perhaps because of the legacy from BR, London Overground uses end-of-line directions, as seen on pages 25-27 of the Signs Manual PDF: http://www.tfl.gov.uk/tfl/corporate/media/designstandards/assets/downloads/overground/OvergroundSignsStandardIssue01.pdf