How DOOH Advertising Drives Real Impact: From VAC and Reach to Attention

Digital Out-of-Home (DOOH) is about more than just impressions and reach. To truly understand the impact of DOOH, we must combine industry standards like VAC (Visibility Adjusted Contacts) and “Outdoor Impact” with attention—the engagement that drives actual behavior and brand effect. Here, we explain how JCDecaux leverages VAC, reach, and screen density to maximize attention in the world of outdoor advertising.

Attention is the decisive factor when analyzing the value of DOOH. Impressions and reach indicate how many people could have seen an ad, but without actual attention, the impact remains limited. Industry leaders and major media agencies, such as Dentsu in their multi-year “Attention Economy” study, are increasingly pointing toward attention-based metrics as the next frontier, as they explain real-world impact far better than mere viewability.

To understand what DOOH contributes to the media mix, it is essential to distinguish between viewability, verified impressions, and the attention that drives results.

Viewability: Can the message be seen at all?

Viewability in outdoor advertising refers to whether a message is physically perceivable in its environment. In DOOH, this is defined by a screen’s placement, angle, size, brightness, and whether there are any visual obstructions. Digital screens in bus shelters or other street furniture often have high viewability because pedestrians are in close proximity, moving slowly, or standing still, providing them with the necessary time to absorb the message.

Conversely, standalone digital billboards along major highways may generate high traffic volumes and many potential contacts, but the actual ability to process the details of the creative is lower due to high speed and the primary focus on driving. In practice, this means two DOOH sites with identical reach can deliver vastly different levels of actual attention.

Verified Impressions: When the audience is in the zone

Verified impressions represent the next level of DOOH measurement. This process links playback data from the DOOH network with traffic flows, mobility data, and screen placement. We count only those exposures where the target audience was physically present within a defined observation zone when the creative was displayed.

While these third-party verified contacts provide a more robust measurement than traditional estimates—giving advertisers greater confidence in campaign delivery—even verified impressions tell us little about the attention the message actually received, and thus the business impact it is likely to generate.

How JCDecaux Measures Impact: VAC, Reach, and Screen Density

At JCDecaux, our planning and reporting are primarily based on three foundational metrics: VAC (Visibility Adjusted Contacts), reach, and the number of screens. Together, these provide a structured framework for understanding potential campaign impact before we move toward more qualitative metrics like attention.

• VAC (Visibility Adjusted Contacts): VAC quantifies the number of contacts adjusted for visibility—essentially, how many actual exposures a campaign likely achieved based on human movement patterns and the visibility of the site. VAC is an established industry standard for (D)OOH measurement. In Sweden, JCDecaux and our industry peers use the “Outdoor Impact” framework to ensure consistent planning and comparison. VAC accounts for traffic flow, pedestrian paths, distance, viewing angles, and dwell time, making it a more qualified metric than purely theoretical contacts.

• Reach: Reach describes the proportion of the target audience reached during a given period. In DOOH planning, we use reach to ensure sufficient breadth—not just high frequency, but broad coverage of the right people. Using Outdoor Impact data, we optimize network selection to maximize reach within defined segments while maintaining high VAC levels.

• Screen Density: The number of screens is a tactical planning metric that influences both reach and frequency. While more screens can increase VAC and reach, the combination of location, environment, and dwell time is what determines the attention generated per contact. JCDecaux holds a competitive advantage here: our digital screens are situated in premium locations across Sweden’s 25 largest cities—hubs where people frequently move, wait, commute, or shop. This ensures that every display has a higher probability of being seen and remembered.

Attention: The Key Driver of Effect

Attention describes the portion of an exposure where the recipient registers the creative and processes the message, with the potential to influence attitude, memory, and behavior. In DOOH, attention is influenced by:

• Dwell time: How long the audience is in the vicinity of a screen.

• Competitive clutter: How many other messages are sharing the screen.

• Contextual relevance: Timing, location, and target audience alignment.

• Creative clarity: The simplicity and visual impact of the message.

Longer dwell times at retail-adjacent “select” sites or transit hubs allow for more complex narratives, while high-traffic areas require simplified, high-impact messaging to capture attention. As Dentsu’s “Attention Economy” program demonstrates, attention is more strongly correlated with brand recall and sales response than traditional volume metrics, driving the shift toward attention-based KPIs.

Why Placement is Critical

Placement and context are decisive for maximizing attention. Screens in locations where people are naturally waiting, changing transport, or slowing their pace (such as transit hubs, city centers, shopping malls, or parking garages) tend to generate more attention per verified impression than screens in high-speed traffic environments.

When combined with creative activations—such as integrated physical elements or high-impact digital formats like MetroVision (Europe’s largest digital subway format)—the potential to drive brand preference and purchase intent increases significantly.

Conclusion for Media Buyers

For media buyers, this evolution means looking beyond raw impressions. The best format for reach is not always the best format for attention. In practice, this means:

1. Planning should be based on a combination of reach, verified impressions, and attention potential across different environments.

2. Optimization should focus on dwell time, spot length, loop sequences, and creative complexity, rather than just CPM.

3. Evaluation should focus on actual outcomes—searches, website traffic, store visits, and sales—where DOOH is linked to other digital data.

A well-considered combination of the right format, relevant environments, and adapted spot lengths often results in fewer, but far more valuable, contacts. It is these moments of genuine attention that ultimately drive both short-term response and long-term brand equity within the media mix.