Auto Trader  is planning to upgrade its iPhone app with push notifications that would enable a user to register their interest in cars of a certain make, age or price,  then receive a notification when someone lists one that matches their requirement. Nick Gee, mobile director at Trader Media Group, which publishes Auto Trader revealed the plans in a meeting with Mobile Marketing this afternoon.

Auto Trader has been in print since 1977 (under its original name of Thames Valley Trader), online since 1996, and on mobile since 2009. The firm started with a mobile site, which it optimised for iPhone users when it saw that half the traffic to the site was coming from iPhones. In fact, last month, Gee told me, there were 7m searches across the Auto Trader mobile platform, which now also includes iPhone and Nokia apps. Of these, 5m were executed on iPhones.

The iPhone app is good to look at and easy to use. It’s populated by mobile-optimised versions of listings from the print and online channels, plus bigger, dedicated mobile listings that car dealers, who are responsible for the majority of Auto Trader listings, pay for. These typically get twice the amount of calls from interested buyers, Gee told me. There’s no in-app advertising, as the entire content of the app is advertising, albeit classified, rather than display.

Auto Trader runs its own mobile team, which develops and populates the mobile properties. It also offers a mobile site-building service to car dealers, enabling them to get a presence on the mobile web, that users can click through to from one of their Auto Trader mobile ads. Next year, Auto Trader will add new cars to its listings. An Android version of the app is also in the offing and Windows Phone 7 is under consideration.

Gee told me candidly that the apps were developed to do things that can’t currently be done through the browser, and, currently at least, offer the richer experience. Despite this, traffic to the mobile site is running at the rate of half a million unique visitors per month, which is what the figure was when the iPhone app was launched. The company doesn’t deal in app download figures, but says it had 300,000 unique iPhone app users last month. “We also know that 80 per cent of the people who downloaded the original version of the iPhone app in March are still updating it,” Gee said.