Adshel won the contract, which will run for ten years, following a competitive pitch. It previously held the business, but under the new terms will increase the number of advertising panels across the West Midlands.
Starting on 1 July, the deal covers areas in which the bus operator Centro runs its services. This comprises Birmingham, Dudley, Coventry, Walsall and Wolverhampton.
The award of the West Midlands contract, the second largest outside London, comes ahead of pitches for many of the remaining Network Rail outdoor contracts, a large proportion of which are held by Maiden.
Julie France, the managing director of Adshel, said: "We are delighted that Centro has chosen Adshel as its partner for advertising. This new contract will enable Adshel to strengthen its coverage of the UK and reinforces its position as the leader in the six-sheet market."