It is important to bear in mind the person behind the wheel when developing large road and rail vehicles. The German Aerospace Center (DLR) Institute of Transportation Systems has created a simulation environment for this purpose; it is part of its Application Platform for Intelligent Mobility (AIM). The modular mockup enables a realistic replication of the environment occupied by drivers of large vehicles – driver's cabs of large vehicles such as trams, lorries and buses can be installed. As a result, researchers are able to study the functional, design and operational requirements that need to be met for large vehicles. The people-focused development process provides drivers with the best possible support. Depending on requirements, the modular mockup can be integrated into DLR's various laboratory environments, such as the Virtual Reality Lab (with its 360-degree projection) or the dynamic driving simulator.