How does Outdoor Impact calculate an “actual” contact?
When we talk about VAC (Visibility Adjusted Contacts), it essentially boils down to one question: how likely is it that a person passing by actually sees the advertisement? Outdoor Impact answers this by combining traffic and movement data, detailed information about every individual site, and models that simulate how people see and perceive messages while in motion. The result is a visibility factor per site, which is used to convert gross pass-bys into VAC—providing more realistic, visible contacts rather than just “how many people passed by.”
Source: JCDecaux, “OOH Audience Measurement 101,” with references to ESOMAR, WFA, etc.
In practice, this means that factors such as distance, angle, height, speed, size, and visual noise around the site are of great importance. A display at a bus shelter or in a pedestrian walkway can yield high VAC despite lower traffic volumes, while a site along a fast-moving road might yield lower VAC despite a high number of pass-bys. Furthermore, exposure time and probable eye contact are factored in—how long the display is actually within the field of vision and whether it is located where people naturally cast their gaze. This type of “eyes-on” or VAC metric is recommended in global guidelines for OOH measurement and is highlighted as the standard currency by several industry players.
Source: MediaPost, “Why Out-of-Home Is Becoming The Model For Audience Measurement.”
Once VAC is calculated, Outdoor Impact can calculate reach and frequency at the campaign level. The point is that two sites with the same number of gross pass-bys can provide completely different numbers of VAC, depending on visibility and exposure time. This allows OOH and DOOH to be compared more fairly with other media: whereas many channels still report relatively generous impressions, modern outdoor measurement delivers a refined figure representing how many people actually had a reasonable chance to see the advertisement.
Source: JCDecaux, “OOH Audience Measurement 101,” with references to ESOMAR, WFA, etc.
