It is yet to be united with production body work but beneath the familiar lines of this high-riding 3-series Touring lurks the mechanical basis of BMW’s second-generation X3. The odd-looking prototype is being used to rack up development miles ahead of the SUV’s planned launch late next year. The new Audi Q5 and Mercedes-Benz GLK are not far from launch,and BMW knows it will have its work cut out emulating the success of the first-generation X3. BMW plans to introduce a smaller X1 off-roader at the more affordable end of its line-up towards the end of the decade, so the new X3 is set to grow slightly in size. Length increases to 4.7 metres with width up to 1.9 metres, up from the current models’ 4.5 metres and 1.85 metres.The increase in dimensions will help answer one of the biggest criticisms of the original X3, its lack of rear seat legroom and poor access to the back seats. It will also justify an increase in price.Underpinning the new X3 is a new platform structure that brings together various mechanical elements from the 3-series and electric systems from the X5. It will be produced in BMW’s Spartanburg plant in America, alongside the X5 and X6.BMW has tasked the X3 engineering team with delivering class-leading dynamics, and it will be equipped with the latest xDrive four-wheel drive system, complete with BMW’s torque-vectoring system to apportion drive between the rear wheels.The 3-series prototype mule pictured here provides a good indication of the ride height that the X3 will boast in production trim.It’s yet to be revealed whether the new car will receive the double-wishbone front suspension of the larger X5 or stick with the MacPherson strut set-up of the 3-Series. The new car’s engine line-up should be familiar from the rest of the range, including the twin-turbo versions of BMW’s 3.0-litre petrol and diesel motors.BMW is also developing a hybrid version of its new off-roader featuring the drivetrain technology unveiled in the X5 Vision at the Geneva motor show earlier this year, which will combine the new twin-turbocharged 2.0-litre diesel engine with an electric motor drawing energy from a stack of lithium-ion batteries mounted in the spare wheel well.