Car Seat Regulations in Germany
*Children under 12 years old and under 150 cms must be in an age and weight appropriate car seat. If a child is under 12 and over 150cms, they don't need to use a car seat.
Children may sit in the front or back of the car provided they use an appropriate car seat/booster. Note that some product liability conditions require the seat to be placed in the back. You may not use a rear facing car seat in the front passenger seat unless the airbag has been deactivated.
Children over 15kg in weight can use a booster seat (as opposed to a 5 point car seat).
If you have used all your car seats, one child (over 3 years old) is allowed to sit in the rear without a booster. However, this must be the heaviest and oldest child, and only if there is no other option.
In taxis, buses and coaches the requirement is waived. Most airlines will allow you to take a car seat in the hold for free, so to be safe, you can take your own. Many taxis in Germany, have build in booster seats. Ask the driver when you get in.
*source www.kvw-mhm.de, as at September 2012
See the information on airlines to find out if you can take a car seat on board the aeroplane.