Reach in OOH

If you’re a business that pays for public advertising, what kinds of questions would you ask to figure out how effective your ads truly are? Would you wonder how many people are seeing your message? The demographics of those people? Whether they fit your target audience?

All of these questions are essential when understanding reach and engagement or, how well your ads are performing for brand awareness, particularly in the context of out-of-home, or OOH, advertising. 

Measuring OOH ad performance can be more complicated than other mediums. Outdoor advertising options don’t exactly provide a practical way to stand on a street corner and manually count every person who looks up at a billboard or passes by a bus shelter.

So, how do OOH advertisers estimate their reach and engagement rate among their potential customers? Read on to learn more about different types of ooh advertising, reach as a measure of OOH ad performance, and what it means for your marketing strategy.

What is Reach in Marketing?

So, what is reach in marketing? A reach metric is a calculation that’s used to measure your advertisement’s exposure to your target audience. Reach is formally defined as the percentage of your target audience who see your message at least once during the advertising campaign.1

What is the Difference Between Reach and Impressions?

In marketing, there are a variety of terms that are used to describe audience receptions to advertisement campaigns. The differences between them are often small, so it’s important to recognize the distinctions between what each actually measures.

In addition to reach, measures called impressions and engagement rate are also used to assess an ad campaign’s effectiveness. Wondering how to calculate impressions? Viewed impressions estimate how many times a person will view your ad throughout the course of your advertising campaign.1

While viewed impressions account for people who view your ad more than once, organic reach does not. Organic reach also does not imply that people actually ingested your messages, rather just that they could have.

How is OOH Reach Calculated?

OOH mediums calculate reach and other audience measurements differently than social media platforms or digital marketing mediums. Because OOH doesn’t have digital data on clicks, views, or scrolls on a social media platform, a marketer has to be more creative. Outdoor advertising reach is calculated through a combined analysis of traffic data, census information, consumer surveys, and experimental research.

A marketer uses two main methods of calculating OOH potential reach: 

  • Daily Effective Circulation (DECs)
  • Variable Adjustment Index (VAI)

Daily Effective Circulation is slightly outdated, while the Variable Adjustment Index is the culmination of more recent advancements in advertising research.

Daily Effective Circulation (DECs)

Daily Effective Circulation is the average number of unique people that pass by an ad. This simple measure uses vehicle traffic data for both independently owned cars and public transportation to determine how many unique people could have seen your ad.1/p>

Despite its frequent use in previous decades, there is a significant problem with this marketing strategy. DECs only measure how many followers may have seen your ad, not how many likely saw it. The next method came about to try and solve this problem.

Variable Adjustment Index (VAI)

Advertisers were not satisfied with the rough estimates provided by DECs. The Traffic Audit Bureau (TAB), now known as Geopath, came about to try to solve this problem. TAB was able to refine the data provided by DECs by incorporating research on consumer behavior and attention.2

They conducted studies using eye-tracking technology to learn where people looked as they drove. Through these studies, they determined what percentage of people in traffic actually pay attention to advertisements as they drive past them.

This data is applied to DECs to produce a scale called the variable adjustment index, or VAI. The VAI is regarded as the most up-to-date and accurate measure of reach, as well as other measures such as multiple impressions, for OOH media.

VAI is frequently used in combination with census data. Census data provides valuable demographic information to help advertisers determine if their messages are actually reaching their target audience.

How Do I Know if I Have Good Reach?

Now that you know more about unique reach and how it is calculated, you may still have questions. What does reach mean for your individual ad campaign? How do I know if my ads have a good reach or engagement metric?

Typically, the higher the percentage, the better. However, unless you have training in advanced marketing analytics and data analysis, it can be difficult to crunch the numbers of the unique reach by yourself. It’s generally acknowledged that consulting an outside advertising expert is the best strategy for both calculating and interpreting your reach and engagement metric.

Reach New Heights with True Impact Media

Measuring audience reach is a crucial part of marketing analytics for all advertising. For OOH specifically, reach data can seem elusive. However, with the right knowledge, you can create a high-impact marketing campaign that checks all the boxes. The importance of outdoor advertising in your marketing efforts is ten-fold.

If you are interested in OOH advertising, True Impact Media is here to help. We can provide guidance on choosing locations and mediums, as well as using our industry expertise to help you plan an entire advertising campaign from start to finish. If you are looking for a guide to OOH advertising costs we have you covered.

Reach your full potential through a personalized OOH campaign with True Impact Media today!


  1. Out Of Home Advertising Association of America. OOH Glossary of Terms.
  2. Geopath. Our Organization.
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