Grand Theft Auto III - The Definitive Edition

Probably the hardest of the emergency vehicle missions as it requires you to do it in one sitting. I did this on Portland at the start of the game as I found it easiest. 

Once you get in an ambulance (you can either find one at the hospital or can normally get one to come to you if you kill a couple of people close to each other) hit to start the mission. It will task you with picking up patients and taking them back to the hospital. On level 1 you will have 1 patient, level 2 gives 2 patients etc. The ambulance can only hold 3 patients at a time as a maximum so bear that in mind. 

Once each level starts, I found it best to pause and examine the map to find the best route to patients, making sure to remember that there can be at most three in one collection before you have to return to the hospital. Each patient you collect will reward you with additional time that level. Normally after the first few you can take your time a bit more. Try to avoid hitting things with the ambulance or going around corners too quick as it can easily tip over or set on fire and you’ll fail the mission. 

Completing level 12 is required for 100% completion but only has to be done once.