What characteristics does a modern subcompact have to have? It has to be small, of course - which the Opel Karl certainly is. It also needs to be modern, and today that means having good communications systems.The Karl is the only vehicle in its class with a personal online and service assist. The system is called OnStar and offers a broad range of safety and comfort features. If a collision triggers the airbag, for example, the car automatically connects with the OnStar center and, through it, with the emergency services.