Montreal’s Hivestack is continuing its push to be one of the global leaders in digital out-of-home, partnering with Clear Channel Outdoor Americas to make one of the U.S.’s biggest outdoor advertising inventories available on its platform.

In addition to its direct sales, Clear Channel will make its PMP buys available programmatically through Hivestack’s digital out-of-home SSP, as well as in an open exchange through Hivestack Ad Exchange.

Clear Channel’s U.S. inventory includes digital billboards and posters, spectaculars, airport media, bus shelters and commuter rail stations that reach over 100 million people monthly. Globally, Hivestack currently activates against 343 billion monthly impressions.

Hivestack’s founder and CEO, Andreas Soupliotis, says the partnership gives the Hivestack SSP a level of scale that is “unprecedented” in the rapidly growing but still relatively new programmatic out-of-home space. Through omnichannel DSPs that are integrated with Hivestack, it also allows digital marketers to buy and measure Clear Channel’s inventory alongside digital and mobile buys.

This is the latest big move Hivestack has made this year to increase its reach, having also teamed up with The Trade Desk, Talon and Bombora.