If you believe that someone on the bus has gone into cardiac arrest, you should call 999 immediately and provide them with as much information as possible. If there is an AED onboard, it would be best to inform the operator so they can retrieve it and begin treatment while emergency services are en route. AEDs on buses provide a much-needed layer of safety and security to passengers and staff alike. By having AEDs onboard, you can ensure that any potential medical cardiac emergency is dealt with quickly and effectively, giving victims the best possible chance of survival.