Underground advertising is measured on opportunity and frequency, not on clicks. Understanding what the numbers do and do not say is the difference between a useful evaluation and an argument after the fact.
Coverage and frequency
Coverage is the share of your target audience with at least one opportunity to see the campaign. Frequency is how many opportunities the average person in that group had. The out of home audience currency models both from passenger data, site locations and visibility characteristics.
Station entry and exit counts
TfL publishes annual entry and exit counts by station. They are useful for sizing a station and comparing two of them, and they are not a campaign metric: a count of journeys is not a count of people, and a commuter passing twice a day appears many times over.
What can be measured beyond that
- Brand lift studies — pre and post surveys against an exposed and unexposed group. Worth it on larger campaigns, not on a two-week poster burst.
- Footfall studies — for retail, matching campaign windows against store traffic.
- Play-out reporting — for digital, confirming what ran, where and when.
- Proof of posting — for paper, confirming the site went up as booked.
We do not publish performance figures from past campaigns anywhere on this site unless the client has approved the number and its source. A case study without a citation is a claim, not evidence.
Sources and references
- The out of home audience currency — Coverage and frequency measurement for the sector. Specific release to be cited before launch.
- Transport for London — network and station data — Station counts, line data and fare zones. Specific datasets to be cited before launch.
