In April, Mercedes-Benz will introduce the new GL-Class (X 166) to public and media at the New York Auto Show. The last phase of development undergoes undeterred as a fleet of test prototypes has been recently spotted on the outskirts of Stuttgart. The black camouflage has come off, so more details of the massive SUV are now becoming visible, like the headlights, beefy grille and bumpers and the elegantly designed LED tail lamps. Most probably, given the mud that's accumulated on the wheels and sides of the body, the snagged GLs were returning to the R&D Centre from a series of offroad trials custom-made to evaluate the potential skills of this new SUV generation.