You could have made all the same ridership arguements about reopening the North London Line to Stratford and look how busy it is now!

Considering what traffic in Watford is like whenever I visit I would expect abstraction from both bus and car traffic as well as new journey opportunities. The link caters for travel to Watford from a large slice of north west London and travel to the Harrow and Wembley areas from Watford and interchange at Watford Junction for journeys that would otherwise require travel to central London.

I never understand why some people are convinced that public transport is only used to commute to Central London.