From Transport for London
A trip on the London Underground (or Tube) always has a lot of advertising posters, some quite clever. But over a century Transport for London have prepared some very clever messaging. This poster was released in 1981 and is dated a bit by the use of the funky font which gives away the era. You can also take a look at this design blog that features one hundred of the best posters that have been posted for the London Underground from 1911 on.
And below, one of my favourites from London Northwestern Railways: