Mercedes reveals curvy four-door coupe concept at Frankfurt show, with world-beating aerodynamics rating

Amongst all the production-ready new cars at the Frankfurt Motor Show, there is now (of course) a new forward-thinking design study: the appropriately-named Mercedes IAA Concept.

Design to preview Merc's future large car design direction, the Concept IAA is a vision of things to come in the next decade from the S-Class luxury car range. Although the over-exaggerated features won't make it to future road cars, the brand is giving us a look at the future of Mercedes car designs.