How to Calculate Impressions for OOH Advertising

Estimated read time: 

4 minutes read
In this article...

Advertising is believed to reach £29 billion this year, up 3 percent more than last year and 35 percent since 2010. With this number continuing to rise incrementally. In fact, the amount spent on marketing in the United States has nearly doubled since 2014, with this trend also prevalent in the UK and similarly developed economies.

There are various reasons behind this, including the simple fact that OOH campaigns are renowned for being easy to measure in terms of engagement, impression and ROI. Historically, the same could not have been said for most offline marketing channels, particularly out-of-home (OOH) media and billboards.

This is no longer the case, however, with the OOH advertising industry having developed several innovative ways of calculating impressions and measuring the effectiveness of campaigns. We’ll break these down below, whilst asking how you can determine whether your campaign has been successful.

What Methods and Data-sets Allow you to Measure OOH Impressions

The number of impressions (or views) generated by outdoor ads is central to the success or failure of any campaign, and this is the single most coveted metric amongst marketers and business owners.

There are several different methods used by brands to calculate ad impressions, depending on the location of your billboards and the resources available to your firm. These include:

Travel Surveys

We start with the industry standard for calculating OOH impressions, with travel surveys having being used successfully throughout the digital age.

Ipsos Connect is one of the leaders in the field, with the group having conducted travel survey fieldwork that has seen more than 50,000 respondents participate since its inception. These surveys use digital ‘MobiTest’ devices to track respondent’s movement, whilst garnering highly granular and sophisticated data sets that offer huge value to marketers.

This includes the real-time location of participants, their speed and direction of travel, along with their altitude and the temperature of the surrounding environment.


From an OOH advertiser perspective, selected data sets can be overlaid with a comprehensive map of outdoor advert locations, offering an insight into the traffic flows that pass individual billboards.

Incredibly, this data will also tell you how many people faced your advert and how long they stood in front of it, and this can offer a unique insight into the level of engagement that exists between a brand and its customers.

By being able to track a respondent’s movements after they’ve engaged with an outdoor advert, brands can also determine the effectiveness of their communications and additional conversion metrics.

Local Government Data and Traffic Levels

Whilst travel surveys remain the most effective and technologically advanced way of garnering data and calculating impressions, there are other methods and data sets that can be leveraged by brands (particularly those who have installed large-form roadside billboards).

One option is to access data from local government that details the traffic levels in targeted areas, which can then be cross-referenced and mapped against OOH post sites.

The Department of Transport in the UK is known to keep maps that details traffic flows and levels on Britain’s comprehensive A-road and motorway networks, for example, and brands can search any area in the UK before pulling up a series of selected “count points”.

leeds mapFrom here, you can download specific traffic data that pertain to your ad sites, affording you an insight into how many impressions you’re likely to have achieved in each location.

You can also seek out further data relating to traffic flows and the speed of vehicles as they pass, helping you to understand potential engagement levels and how much exposure your message has benefitted from in a host of different locations.

3D Maps and Visibility Adjustment Indices

Some brands may also use three-dimensional digital maps of outdoor space and interior locations such as tube and train stations (which remain popular outlets for smaller billboards and OOH messaging).

These accurate maps are also used to replicate the type of 3D interiors found in shopping centres, making it possible to measure the flow of traffic and views in OOH environments that have been historically hard to measure.

These maps can also be combined with so-called ‘Visibility Adjustment Indices (VAIs), which essentially factor in the physical characteristics of an outdoor structure or ad location to provide more accurate impression calculations.

3d render shopping

These include everything from the precise placement of the unit to the distance at which an ad is typically viewed and its size, and this detail-oriented approach creates a far greater level of insight whilst identifying any potential issues that may impact on engagement.

This is an important consideration, as whilst these methods of measuring impressions are becoming increasingly effective it remains hard to determine how many people have actually absorbed a message.

To compensate for this, some of the more advanced OOH measurement systems incorporate algorithms that have been built on in-depth eye-movement research and accepted psychological theories.

By leveraging these principles in conjunction with travel surveys and local government data, it’s far easier to gauge and analyse audience behaviour in the most effective manner.

These measurement systems can also be used to convert viewable impressions (OTCs) into actual viewed impressions (VACs), providing the final frontier for brands in the field of cost-effective outdoor advertising.

The Last Word

Another huge advantage of these advanced measurement systems is that they can help with the development of successful outdoor advertising and integrated marketing campaigns.

More specifically, these systems can be used to inform your decisions as to where OOH media should be placed, whether you’re looking to install 48 or 96-sheet roadside billboards or smaller posters in bus and train stations.

By comparing available ad sites with aforementioned traffic flows and data, you can plan a more effective campaign that generates an optimal number of impressions, significant engagement levels and a superior return on your marketing spend.

It’s also important to remember that whilst calculating ad impressions is central to any successful OOH advertising campaigns, you must apply the same level of analysis and insight across every single stage of the customer journey.

This involves leveraging different systems that measure both engagement and brand actions so that you can determine the profitability of your outdoor campaigns and their effectiveness at translating views into conversions.

Book your billboard today.
Book your billboard today.

Related Articles