Is there some way to handover your car to another driver while racing? So you can do teamracing, like Lemans etc., where serveral drivers race for a period of the race?

Yes; someone may need to correct me since it has been awhile since I've done it but:

The driver waiting will press the little 't' next to the driver he is teamed with before the pitstop happens. The current driver also needs to press the t or do something before / during the pit. Then after/during the pitstop the drivers are swapped.

The first driver will want to be sure to put the car into neutral, otherwise it will stall when he gets out.

Or you could make a pit stop, press T next to the driver who wants to take over and he presses the green T. Similar though. All the things Tim said also apply.

Quote from blackbird04217 :

Yes; someone may need to correct me since it has been awhile since I've done it but:

The driver waiting will press the little 't' next to the driver he is teamed with before the pitstop happens. The current driver also needs to press the t or do something before / during the pit. Then after/during the pitstop the drivers are swapped.

The first driver will want to be sure to put the car into neutral, otherwise it will stall when he gets out.

The stopping driver presses the T when his pitstop finishes, it doesn't work before...