Primesight has held the outdoor contract on the Glasgow Subway for 20 years. The win means it will continue to sell traditional and digital advertising for the next three years, with the possibility to extend by another two.
A Primesight spokesman said the contract is estimated to be worth more than £8m over five years.
The estate currently includes 20 digital six-sheet screens and, following the retention, Primesight said it would be expanding the digital offer in the subway.
Last year, Glasgow Subway became the first undergound system in the UK to offer Wi-Fi to passengers, ahead of the London Underground, through a partnership with the Wi-Fi network, The Cloud (now owned by BSkyB.)
Keith Lammie, regional director, Primesight, said: "In the past five years, we have delivered some fantastic and unique campaigns for our clients in the Glasgow Subway.
"From special builds and wrapped trains, to live feeds and digital screens, we continue to push innovative offers for our clients. We have put forward some ambitious development plans and it will be with pride to see these come to fruition."
The regional transport partnership for west Scotland, Strathclyde Partnership for Transport (SPT), is undertaking a £290m upgrade of the Glasgow Subway, which will include the introduction of driverless trains and Oyster card-style "smart ticketing".
CBS Outdoor, who also pitched for the contract, had not responded to requests for comment by the time of publication.
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