Gaming the system - ambulance response times

It turns out that if emergency services try to chase response times then the public can get screwed over, in a very real and non-reversibly fatal sense:

Emergency services were called at 23:15 GMT and a paramedic arrived within 15 minutes. The paramedic contacted the control room three times asking for the ambulance to arrive sooner, but it did not arrive until 01:00 GMT the next day, Mr Nelson's family said.

Presumably this was a motorcycle paramedic, who will carry some fluids though probably not blood and certainly not more than a few pints of them. The unfortunate 26 year old Mr. Nelson is described as suffering from haemorrhaging, which was almost certainly internal and hence could not be successfully treated without surgery; all the paramedic could do was buy time pending transfer of Mr. Nelson to a hospital with an on-call surgery team, so that Mr. Nelson could a) receive whole blood in volume to replace his loss and b) be opened up so that the surgery team could clamp the offending major blood vessel to stop the loss. Unfortunately it seems that the required ambulance took another 90 minutes to arrive, which was way too late.

So why did the ambulance take so long? We can reasonably assume that the paramedic made a diagnosis of internal bleeding and called in for an urgent transport, so the available ambulances must have been elsewhere:

He added: "It seems that if they meet the target for the whole of the east of England, it satisfies the government target but the danger is they focus on urban areas where they can easily hit the target and rural areas get neglected.

Bingo! Why is this? Here's one possible explanation.

Suppose you have a reasonable-sized city (e.g. Reading, Oxford) surrounded by a fairly large rural area. Your ambulance, fire and police stations are somewhere in the city. At regular times you have a small number (say 2-4) of available ambulances, waiting to respond to calls. Most of your calls will come from within the city as not only do you have most of your people there but they are in an environment more likely to cause accidents (heavy traffic, concentrated drinking etc.) Anticipating this, you station most if not all of your ambulances around the city ring road and near major junctions so that they can either head straight in to the city, head straight out to the rural towns in their sector, or drive around the ring road to access a different sector. Your hospital will be within the city so your vehicles will go "green" (available) there; you can direct them to go straight to the next call or send them to one of your vacant ring-road sectors.

Blakeney, the home of Mr. Nelson, is 80 minutes from Great Yarmouth and 50 minutes from Kings Lynn (the nearest major towns). Without wanting to second-guess Norfolk ambulance control I'd imagine that they might have had an ambulance stationing point near Cromer or Swaffham, but someone else called first and that ambulance was taken; once they received the priority call from the paramedic, the ambulance would have nearly an hour of driving just to reach Blakeney. Because the incident happened on a Thursday night they probably had fewer ambulances available than on the busier Friday or Saturday nights, and because it happened around 11pm it was during the busiest period.

If the East of England Ambulance Trust wanted to reduce the incidence of long waits for ambulances in rural towns, it would have to position more ambulances way out from its major urban centres. The problem is that this would increase response times for the bulk of incidents during busy times when the remote-stationed ambulances were required near the cities. For the sake of significantly improving response times in relatively rare scenarios (multiple incidents away from the cities) you're going to be significantly impinging on your common-or-garden city incidents.

So what's the ambulance response time target?

Immediately life threatening – An emergency response will reach 75% of these calls within eight minutes. Where onward transport is required, 95% of life-threatening calls will receive an ambulance vehicle capable of transporting the patient safely within 19 minutes of the request for transport being made.

The NHS has at least addressed tail latency here ("95% within 19 minutes") but the problem is that this is a national target. It's much easier to meet in the densely-populated southeast than the more sparsely populated areas of the country. In the latter case, an ambulance trust's best bet is to concentrate resources around towns as discussed above, since they won't have a prayer of meeting "75% within 8 minutes" otherwise. It also allows wildly increasing times for 1/20th of the patients - if you can't get an ambulance to them in 20 minutes, there's no additional penalty for taking 90 minutes to reach them despite the fact you're identified these patients as needing onwards transport.

The dominant problem here is a national service (the NHS) requiring national targets for regional services, not making any allowance for the wildly different demographic distribution across the country. There's nothing conceptually wrong with the form of the target, but they need to vary the numbers as populations become less dense. You'd expect the tail latency requirement to remain fairly constant, but the initial response time to increase as population density decreases, and you should also add a 99% latency requirement (say, 30 minutes) to reduce the long waits for needy rural patients. Your response targets may no longer fit within a soundbite, but at least they are now aimed at saving lives across the country.