INGOLSTADT, Germany - A senior Audi executive has urged a design overhaul in response to criticism that the brand is making "lookalike" vehicles which differ only in length.Development chief Wolfgang Duerheimer said: "I've heard criticism from some markets; in the case of certain models. we're still getting there."In future I will join forces with our designers to ensure that model ranges can be more readily distinguished."THAT’S AN A4…NO WAIT...The automaker’s A4, A6 and range-topping A8 share many design elements and a stronger family resemblance than comparable models from BMW or Mercedes-Benz. Duerheimer said: "Naturally, an A8 customer must find features which set his car apart from an A4 or an A6.”He urged in-house designers to be more bold and experimental while retaining what he called Audi's bechmark "design precision".'LOOKING LIKE RUSSIAN DOLLS'Audi interiors are known for restrained upmarket ambiance rather than opulent features. Duerheimer said designers could learn from luxury automakers Bentley and Bugatti, each owned by Audi's parent company VW.Here's what some Wheels24 readers had to say about Audi's model range:GTO said: "Audi makes super nice cars but the design is getting a bit like Russian dolls"Metar911 said: "You clearly have never seen a A4, A5, A6, A7 or A8 in real life! A4, A6 and A8 are the same. Apart from the inside which are miles apart on each model. The A7 and A5 look completely different."James said: I'm surprised that it took Audi headoffice so long to see that these cars all look the same. I battled to see the difference even though I personally work for Audi south Africa, how much more for a layman?"Main image quiz - Even some of the Audi guys got it wrong in the comments. The correct answer is 2011 Audi A6 (top) and 2012 Audi A4 (bottom).So, can you tell one Audi from another or are you as stumped as many drivers when it comes to spotting their differences? Email us and we'll publish your thoughts or share your view in our Readers' Comments section below.Follow the Detroit auto show with Wheels24 on our Detroit show ection.