In America if you call 911 to report an emergency, several police cars, a fire truck and often an ambulance will all rush to your house.

在美国假如你打911报告紧急情况，警车，救火车，还有救护车就会立刻冲到你门口。

youdao

This is an emergency. Please call an ambulance.

情况危急。请叫救护车。

youdao

If you feel it is an Emergency problem (e. g. chest pain...) you should call an ambulance at 911 and go to Emergency Department of Saint John Regional Hospital.

当你遇到紧急的问题(如胸痛…)，你应拨打911叫救护车，去圣约翰地区医院的急诊室看病。

youdao

Two men were injured when their car crashed with an ambulance answering an emergency call with its blue lights on.

BBC: Ambulance crash

So when do you just tough it out, and when do you head for the emergency room, or call an ambulance?

MSN: When to go to the ER with the flu

However, the Surrey and Sussex Healthcare NHS Trust said if an ambulance needed to attend an emergency call then it would be "released immediately".

BBC: NEWS | UK | England | Southern Counties | Ambulances 'queue' to enter A&E