Measuring outdoor advertising seemed to be moving fast-forward the past few years from an archaic count of cars passing billboards to something far more high tech: GPS-loaded devices capable of recording each time a car passed a billboard.

Now the process looks to be taking a huge step backward, at least in technology.

Come early next year, there will be a new standard for measuring outdoor audiences, called Eyes On, based on the very system of traffic counts these new technologies were intended to replace.

Eyes On was developed by the Traffic Audit Bureau for Media Measurement and has received the backing of the Outdoor Advertising Association of America and virtually every outdoor company and media buying agency as the new standard of measurement for media buyers.

In its simplest form, Eyes On is a mathematical formula that will take existing traffic counts and parse them into demographic groups.

Eyes On addresses two major shortcomings of the existing system. First, it promises to deliver credible data on people who actually see the ads, whereas the traffic count method only revealed the traffic that passed by a billboard, with no indication that anyone saw the ad as the car went by.

Eyes On data can also be incorporated into multimedia schedules, which is difficult with traditional traffic count data, making it easier for media buyers to evaluate the effectiveness of out-of-home campaigns against other forms of media.

For a time, TAB considered using a GPS-based system from Nielsen Media Research but then dropped it as impractical.

"Our goal is to provide data in all 200 markets where we conduct audits and report on about a half-million pieces of inventory across those markets," says Joseph Philport, president and CEO of TAB. "The cost of any survey, GPS or anything else, is too expensive to cover that range of markets."

Using GPS would require creating an enormous panel of respondents who carry the device, says Erwin Ephron, a media consultant working with TAB on Eyes On. "To be accurate, it would require a minimum of 25,000 respondents [in most markets]."

And it would not address the most critical issue: whether people are actually seeing the billboards.

Outdoor isn’t like other media, television, for example, where a relatively small sample can accurately reflect viewing or listening by the overall population. There's the reasonable presumption that a television viewer who tunes into a specific network will be exposed to ads that air on that network.

By contrast, that fact that someone is recorded as driving past a billboard, by GPS or some other survey method, does not establish that the person in that car actually saw the billboard.

Media buyers say the new system is superior because the new data will be more credible and easier to use.

"The problem with outdoor is that everybody discounts the numbers because it’s common sense that, if you drive past a billboard every day, after a while you don’t notice it," says Bill Reynolds, vice president and head of media for IPG agency Erwin-Penland. "Anything that credibly lowers the audience for outdoor will increase its value."

The new system will be rolled out gradually next year to get buyers accustomed to the new currency,

With Eyes On, TAB begins with the existing traffic counts and then incorporates demographic data it gathers by having people sit down and simulate driving a car while watching a video of a road with billboards and then tracking their eye movements.

Adjustments are based on how often respondents see ads of different sizes and in varying positions on roads.

"What the whole process gets you to is the ability to report on a board-by-board basis the number of people and their demographic characteristics who pass a board and see what’s on the board in an average week," says Ephron.