If you've got personal breakdown cover you're covered in any vehicle* whether you are a passenger or a driver. Therefore if you're in a car when it breaks down, you can call the RAC for assistance even if you're not driving it at the time.
RAC vehicle breakdown cover covers up to three named vehicles* by registration number no matter who is driving. If you have vehicle breakdown cover, as long as the vehicle is named specifically (by registration no.) on your policy, then you're covered. If you wish to replace one of the vehicles named on your policy, please call 0330 159 1111.
* Non-commercial vehicles only, excluding certain vehicle types.