Volkswagen is planning to extend its existing line-up of four-wheel drives with a new mid-sized seven-seat offering to slot between the Tiguan and Touareg. The new model, which could go on sale in 2011, has been conceived as a rival to Volvo's recently introduced XC60. But rather than using the same platform as Audi's upcoming Q5, the VW will be built on a modified version of the next-generation Passat, known internally as PQ47.Using the lower cost Passat platform means the car will get a space saving transverse engine layout instead of the Q5's longitudinal arrangement. At the same time, it also paves the way for the Volkswagen Group to introduce possible Skoda and Seat variants of the four-wheel drive.Early indications were that Volkswagen may simply stretch the Tiguan in the same fashion as Nissan has done with the Qashqai to create space for a third row of seats. However, with the next-generation Touareg set to be bigger, VW decided the best alternative would be a standalone model based on the future Passat itself set to share a large percentage of its mechanical package with the next Golf, due in September.The plans stem from criticism by US dealers of the Tiguan, which they describe as being too small and too expensive to make much of an impact in the lucrative North American market.