QR codes on OOH work in specific conditions and are wasted ink outside them. The physics of scanning decides which is which.
The scanning test
A QR code earns its space when a viewer can physically scan it: they're stationary or slow-moving, within a few meters, with time to pull out a phone. Apply that test and the format map draws itself.
Where QR codes work
Transit shelters and street furniture: Eye level, pedestrian, waiting audience; the best QR environment in OOH.
Interior transit cards: Seated riders with dwell time.
Place-based screens: Gyms, elevators, bars, retail; close range and dwell.
Airport placements: Long dwell, seated or queued audiences.
Wild postings and posters: Street-level pedestrian formats.
Where QR codes don't work
Highway bulletins and any high or distant placement, and moving media (bus exteriors, truck sides, taxi tops). No one scans a billboard at 65 mph; a code there signals inexperience to anyone in the industry and does nothing for response. On these formats, use a memorable URL or just the brand; branded search is the actual response path.
Best practices where QR fits
Size generously (bigger than feels necessary; distance kills scans), high contrast on a quiet background, place it with a clear call to action, and send it somewhere campaign-specific with a fast mobile page. The QR destination also gives you a clean direct-response measurement stream; see the web traffic attribution article.
Is QR a credible response mechanic overall?
On the right formats, yes; scan behavior normalized post-2020 and eye-level OOH gets real scan volume. Treat scans as bonus direct response on top of the campaign's awareness job, not as the campaign's success metric.