SPY PICS: New Mercedes A-Class spotted testing

The new Mercedes-Benz A-Class has been witnessed circulating Germany's premier testing facility and hallowed racetrack – and also de facto promotional venue – the Nurburgring.

Due to be released in 2018, the next-gen A-Class will address some of the design shortcomings noted for the current model.

This includes extending the roof line for added rear-seat headroom and stretching the wheelbase of the car itself to allow for extra legroom and storage inside the cabin.

There will also be a raft of changes for the powertrains available for the new A-Class, comprising a new 2.0-litre diesel four cylinder, a new 2.0-litre four-cylinder turbocharged petrol engine and a plug-in hybrid model. There are even rumours of a three-cylinder diesel engine being developed for the A-Class.

Other changes to the A-Class will consist of a completely redesigned interior following the design language of the interiors seen already in its older siblings, the C-Class and E-Class. There will also be a greater amount of interior options and application of more expensive materials.

The A-Class's infotainment system will also be updated and will ditch the current car's control wheel for the touch pad used in other models.

If the A-Class is intended to replace the current generation model in 2018, expect a reveal in 2017 at one of the big auto shows – most likely Frankfurt.