What is the speed limit for an ambulance?

An ambulance and a motorbike

An ambulance has to obey the same traffic laws (including speed limits) as other vehicles unless it is an emergency situation. In an emergency an ambulance gets dispensation from obeying certain traffic laws including the speed limit. 

In an emergency it is up to the discretion of the driver to decide the best speed to get to or transport the patient to hospital while minimising the risk to other road users.