Explaining the new ambulance call system and the four groups of calls... Ambulance services are measured on the time it takes from receiving a 999 call to a vehicle arriving at the patient’s location. An improved way of working for ambulance services is being implemented across the country to ensure patients get the right response first time. Category 3 is for urgent calls, such as late stages of labour and non-severe burns. 🚨 🚑 | NHS England