Revenue was up 8 per cent to $162.3 million for the six-month period, with revenue from digital products increasing 27 per cent.

Strong revenue growth in New Zealand helped offset a softening in Australia, where growth was just 6.4 per cent compared to 18 per cent in the same period in 2016.

Underlying earnings were up 7 per cent to $37.2 million and underlying net profit was up 4 per cent to $21.4 million. The company incurred one-off costs of $5.6 million, which included the costs from its attempted merger with oOh!Media, which was blocked by the competition regulator, and impairments for technology trial costs.

It is paying an interim dividend of 6.7 cents, which is 52 per cent of post-tax profit and an increase on last year's 6.5 cents for the first half.

Management expects full-year earnings to be between $90 million and $95 million. In 2016 it delivered earnings of $86.7 million, which was slightly higher than guidance.

In May, APN and oOh!Media announced they were dropping plans to merge after the competition watchdog raised concerns.

"That was an opportunistic merger for us. It would have been fantastic [but] there are clearly other opportunities for us directly related to outdoor advertising ... some of those are larger, some are smaller. We do see [acquisition] as an important growth strategy for us," Mr Herring said.

However, APN is not as interested in content as oOh!Media is, which purchased Junkee media last year.

"Content is normally required to attract an audience. The great thing about outdoor advertising is out audience walks [or] drives past for other reasons. We don't need content," Mr Herring said.

APN's New Zealand team will launch new data research in September that combines mobile data, traffic data, and third party to "assess where those people live, where they reside, where they travel to and how often they travel", outgoing chief executive Richard Herring explained.

The data was not individualised, but could help advertisers understand what kind of people are driving past each billboard.

The information would "prove the value of what [advertisers] are buying", Mr Herring said.

"If we can improve the way in which they make decisions by this information and cut out less valuable sites, for example, it will improve their return on investment. Our view is that if we give advertisers better return on investments they are going to come back."

Neurological research commissioned by APN also found ads placed on moving vehicles, such as trams and buses, was 20 per cent more memorable, Mr Herring said.

During the six months, APN added 16 digital screens, taking its total to 103. Since June 30, it has commissioned a further 24 screens. These deliver up to five times more revenue than classic billboards, but attract electricity costs of up to $20,000 a year and maintenance costs of about the same.

Meanwhile, revenue from its "classic" screens has remained steady and delivered $102.2 million of revenue in the half, while digital billboards delivered revenue of $60.1 million, up from $47.5 million in 2016.

Direct costs, which now included electricity for digital billboards, increased 7 per cent to $103 million.

And overhead costs were up as APN worked on tenders for five contracts, including three it has won; the Tullamarine freeway in Melbourne, buses in Sydney and Adelaide, and Perth's rail and billboards. It is awaiting news on two others - Yarra Trams and Metro Trains in Melbourne.

Mr Herring will step down as chief executive at the end of September. The board is currently looking for his replacement.