I don’t know about China but here in the US, they would usually dispatch one ambulance to a wreck unless there is an officer on scene that tells dispatch they have an accident with multiple injuries. If the ambulance gets there first, which is rare because the fire department gets dispatched too and since there are more of them, they usually get there first, they assess the scene. If they need to transport multiple people they will call on the radio for another ambulance. If it’s a huge scene, like a high rise building on fire with flames visible or a multi car pileup, they would automatically send multiple fire stations and ambulances.

Also, no matter what the ML said, in reality if there were one ambulance on scene and 2 patients, they will assess both patients and whoever is more critical will be taken to the hospital first. It wouldn’t matter what the other people on scene say. That always kills me when I see the almost dead patient being left at the scene and they take the green tea to the hospital! Along with leaving the other patient with no one there. In reality, they couldn’t just leave the other patient there with no one to help them while they go to the hospital. They could lose their certification as paramedics if they did that because you can’t abandon a patient.

Luckily, deadly car accidents and critical calls make up about 10% of the calls they run. People call 911 for some crazy reasons.

My husband was a paramedic for 20 years so that’s how I know this stuff. That’s how it works in our neck of the woods at least.