82% of us leave home each day, and that's where out-of-home advertising comes in. Billboards, the sides of buses, even the little screens at the petrol bowser.

But how do you measure a moving audience? And how do advertisers know they're getting value for money?

Elizabeth McIntyre, Chief Executive of the Outdoor Media Association, talks to Sean Aylmer about outdoor advertising, and how the industry is future-proofing itself.