Advertising on the Underground

One of my proposals is advertising on the Underground, so I have looked into what formats are available. I found that the 48 sheet will be most appropriate.

Taken from CBS Outdoor:

48 Sheet
'The flagship site on the Underground; cross-track 48 Sheets are arguably the most important media property in the UK. Of course they deliver stature, they are large and consumers are a matter of feet away but also add to this the quality and weight of the Underground audience.
However, the true strength of Underground 48s lie in their ability to drive public awareness and debate in London. Demonstrated through various case studies such as the ‘Time To Consider’ campaign – whether you have long copy or a very simple creative execution, commuters welcome the stimuli and will spend time actively consuming your ad both on the platform and beyond.
So when the solution is right in front of you, why would you consider anything but cross-track advertising?'

This is only in Landscape format.