The strengths of digital advertising are well known. One of the commonly cited weaknesses is the lack of any effective means to measure not only the traffic walking by a digital sign, but also a customer's response and level of engagement with the sign.

As interactive digital advertising begins to supplant traditional digital signs, new opportunities are emerging for measuring audience volume and response.

People of a certain age will likely remember being stopped in a shopping mall by someone with a clipboard looking for participants in a survey about shopping habits. If you recall these moments, you likely also remember being somewhat annoyed or brushing the person off with a polite “too busy” as you pointed to your watch.

Retailers knew then, as they know now, that intruding on shoppers in this way detracts from their shopping experience and can build resentment over the long term.

In lieu of live questioning, some retailers now ask shoppers to participate in online surveys, with links usually provided at the bottom of store receipts. Shoppers are enticed with chances to win gift cards or other prizes. The downfall there, of course, is participation. Just like the clipboard-toting mall surveyor, online surveys are easy for shoppers to ignore.

Into this environment comes digital advertising. Before the addition of interactivity, evidence of the impact digital signs had on shopper behavior was pretty much anecdotal – a certain video loop played at a certain time and, coincidentally or not, sales for the advertised item went up.

Interactive or hybrid digital signs, on the other hand, are tailor-made for tracking customer data. They can tell retailers whether or not customers are responding to the signs and, if they are, what triggered their response.

To demonstrate how digital advertising systems can track customer data, let's look at three methods of interactivity:

• Indirect interaction. This interaction is not initiated by the customer. It usually involves some kind of motion sensor that triggers content to change when a customer stops near the sign and, in theory, takes a closer look. The digital advertising system can capture data about what was playing when the customer stopped so the retailer knows what kind of content is most effective.

• Touch screen. This interaction is initiated by the customer and, as such, is more powerful as a research tool. The customer is attracted to a digital sign and given options to touch the screen for sales and promotional information, to print a coupon, to check product availability and so on. The software that runs the digital advertising system can track what was playing when the customer touched the screen and which selections the customer made to see which options engaged the customer most. Tracking time of day against this data paints a picture of what kind of shoppers are in the store at various day parts, so advertising can be better targeted to them.

• Next generation. This option involves the use of cell phones and PDAs. Cell phones are part of the so-called “next gen” in digital advertising. A call to action is displayed on the signs, prompting viewers to text in to receive a coupon or enter a contest. As described in a 2006 article on the Media in Canada Website, this method is akin to tracking the click-through rate on a Website ad because it tells the retailer exactly how many responses there were for each call to action.

With interactive technologies capturing the kind of data that advertisers and marketers want to see, digital advertising – already gaining popularity as a marketing tool - is poised to become an even stronger presence in today's retail landscape.