(Pocket-lint) - TomTom has announced a new free app for Android called TomTom Go Mobile.

The new app replaces TomTom's previous satnav app and completely changes the fee structure, giving you free navigation, speed cameras and traffic for 50 miles a month, every month.

That means for ad hoc users - perhaps finding a way out of a local traffic jam - use of the app will be free. These miles don't accumulate, however, so you can't roll them over from month to month - it's use it or lose it.

After you have used your 50 miles, you'll have to subscribe to retain the turn-by-turn navigation, traffic and speed camera functions, although browsing, route planning and a traffic overview are always available, whether you subscribe or not.

Subscriptions cost £14.99 for 1 year via in-app purchase. If you know you'll want more, you can opt to buy a 3-year subscription for £34.99, saving yourself £10 over those 3 years.

Owners of the existing app will be able to upgrade to the new app and get a 3-year subscription for just 50p.

The change in subscription structure should remove the barriers to app adoption: who wants to gamble on a £30+ app? Now you can download it and at least try it without spending any money.

A regular TomTom Go personal navigation device starts at £149 (Go 40), so opting for the app is the approximately the cost of 10-years of life from a standalone unit. You will have to use your own data connection - for things like traffic - but maps are stored on the device, so it can be used offline or without roaming data.

"We have entirely re-thought our mobile solution so every driver has the chance to try navigation with TomTom Traffic. Now all Android owners can avoid the traffic jams and get to their destinations faster, every day," said Corinne Vigreux, managing director, TomTom Consumer.

The new TomTom Go Mobile app is available on Google Play.

Writing by Chris Hall.