How visibility is adjusted in out-of-home measurement

Today, out-of-home (OOH) and digital out-of-home (DOOH) advertising are planned with far greater precision than simply counting the number of sites and traffic flows. To ensure campaigns can be compared fairly, standardized visibility metrics are used. Concepts such as VA (Visibility Adjustment), VAC (Visibility Adjusted Contacts), and VAI (Visibility Adjustment Index) help both buyers and sellers transition from asking “how many people pass by?” to “how many actually had a realistic opportunity to see and absorb the message?”—in line with global guidelines for OOH measurement.

VA: The adjustment that moves us beyond raw traffic figures

VA is based on gross traffic flows: how many people pass a site by car, on foot, or via public transport. These figures are then adjusted based on the actual conditions required to perceive the site, such as:

• Distance

• Angle to the traffic flow

• Speed (car, pedestrian, bicycle, etc.)

• Height and size

• Potential obstructions and competing visual impressions

Once the visibility adjustment is applied, we obtain a more realistic basis for the next step: VAC.

VAC – Visibility Adjusted Contacts (“Those who actually saw it”)

VAC (Visibility Adjusted Contacts) is the metric used as the “currency” in modern OOH measurement systems, both by JCDecaux and in international guidelines from ESOMAR and the WFA. The concept is straightforward: instead of counting everyone who could have seen a site (OTC – Opportunity To Contact), we only count contacts where the ad was truly perceivable.

To calculate VAC, we combine:

• Visibility-adjusted flows (VA)

• Exposure time and the duration people spend in the environment

• Movement patterns (how people navigate between different sites in a network)

At JCDecaux, we describe this as the core of high-quality (D)OOH measurement: the best systems deliver “viewed impressions”—meaning data on how many people actually saw the ad (VAC), rather than just how many walked or drove past. Outdoor Impact 2.0 uses VAC as the foundational metric for calculating reach, frequency, and total contacts.

VAI – How high is the quality of the contact?

VAI (Visibility Adjustment Index) goes a step further by describing the quality of the contact—essentially, how favorable the conditions are for the message to be read and understood. In systems like Geopath in the U.S., VAI is calculated based on factors such as:

• Surface size

• Road type and roadside positioning

• Distance from the road

• Lighting and surrounding environment

VAI is used to compare visibility quality between different sites, not just traffic volume. This means, for example, that a site with lower traffic volume but a better angle, superior legibility, and longer dwell time can have a higher value than an extremely high-traffic location with poorer visibility.

In DOOH, factors such as spot duration and loop frequency also play a major role in the strength of the actual contact. A short spot that appears infrequently generates a weaker contact than a spot that appears more often and during times when the target audience is truly present, even if the passing volume is the same.

Source: JCDecaux, “OOH Audience Measurement 101 – Who, What, Where, Why?”

Why this matters for OOH planning

Together, VA, VAC, and VAI make it possible to steer OOH and DOOH investments toward locations where the campaign is not just visible on a map, but also:

• Actually seen within the available timeframe

• Readable and understandable

• Possesses a reasonable chance of influencing behavior or attitude

This is at the heart of current global recommendations for responsible and comparable out-of-home measurement: moving away from raw traffic numbers and instead optimizing toward visible, qualitative contacts (VAC) to get as close to “real views” as possible.