Prehospital emergency medical services (EMS) in Switzerland, including ground, air and water-related ambulance services. All certified ambulance services for air, traffic and water accidents are eligible for participation and will be contacted and invited to participate. Additional supporting rescue companies such as rescue squad of the Swiss Alpine Club or of a ski resort as well as lay rescuers will not be included in the analysis. All accidents on medical missions of a prolonged period are analysed. Depending on the available data in the different ambulance services, the study period may extend from at least one year up to a maximum of 10 years.