San Diego’s Ambulance Algorithm

San Diego’s Ambulance Algorithm

Image via Shutterstock

These days in San Diego, people most often need ambulances on Thursdays.

Wayne Johnson knows this because he’s the guy responsible for making sure ambulances can show up at your door within 12 minutes of a major emergency. Johnson’s computer takes data from when anyone in the city used an ambulance over the last three years and predicts the busiest days of the week, times of day and locations for emergencies. Johnson deploys a fleet of ambulances across the city accordingly so they’re ready when the call comes.

Some of these computer predictions make sense: The city needs more ambulances in the afternoon and evenings than overnight because more people are out and about. Some of them don’t: Eight months ago, Saturday was the busiest day of the week, and Johnson has no idea why it changed.

“It’s kind of like a dance,” Johnson said.

Johnson works for Rural/Metro, the ambulance company the city entrusts to help deliver one of its most vital services. The company and the city’s Fire-Rescue Department both answer 911 calls for major medical emergencies. The Fire-Rescue Department aims to have a first responder on the scene of a medical emergency within seven minutes and 30 seconds, nine times out of 10, a target the department misses frequently. This is typically a fire engine.

Rural/Metro’s ambulances are supposed to get there within 12 minutes, nine times out of 10, a requirement that’s recently become more difficult for the company to hit.

The Fire-Rescue Department has a straightforward plan for responding to emergencies. It has engines and trucks scattered across 47 stations in the city, and fire crews typically return to their station after a call. Rural/Metro has a more dynamic plan. It relies on Johnson and his computer.

How the Ambulance Algorithm Works

Rural/Metro’s contract with the city requires the company to respond to high-priority medical emergencies within 12 minutes, and to lesser emergencies within longer timelines. Rural/Metro built its entire ambulance deployment system on meeting those requirements.

To help, the company bought a $300,000 computer program called MARVLIS – yes, it’s pronounced “marvelous” – for Johnson to use. MARVLIS calculates where ambulances need to go based on call histories and the location of the rest of the fleet. The program also shows Johnson what’s happening in real time.

An ambulance screamed down Broadway on a recent afternoon, and Rural/Metro spokesman Michael Simonsen peeked out the window of the company’s downtown office to look at it.

“Medic 68,” Simonsen said. “Where they going, Wayne?”

Johnson studied his screen.

“Hawthorne and State,” he said – an intersection in Little Italy. “Traffic accident.”

The program uses so-called heat maps to show potential trouble spots. Different trouble areas change depending on the time of day and what’s happening elsewhere in the system. Red represents the areas most likely to get a call, green represents the areas less likely to get a call and yellow is in the middle. Blue and purple represent the areas ambulances can respond to within the time requirements. Here’s one MARVLIS snapshot from Wednesday.

Ambulance Heat Map Sept. 18, 2013

Rural/Metro has determined it needs between two and three dozen ambulances on the street, depending on the time of day, to meet its 12-minute requirement. (To lesser emergencies, ambulances go without lights and sirens and they can take longer to get there.) Twenty four of Rural/Metro’s ambulances have an anchored home base that doesn’t change. They reside in fire stations in neighborhoods difficult to serve because of traffic or topography. These include Paradise Hills, Pacific Beach, San Ysidro and Rancho Bernardo.

The remaining ambulances, to use Johnson’s term, “float.” They’re posted at various fire stations or hospitals depending on where they’re needed, and the decisions are guided by strong patterns.

Johnson’s basically the architect of the ambulance deployment. Rural/Metro dispatchers in the Fire-Rescue Department’s communication’s center implement the system day by day.

This map shows a potential Rural/Metro ambulance deployment when all 36 ambulances are on duty. Remember: The system is dynamic and when ambulances are coming to and from calls, the rest of the system is positioned to fill in gaps.

Potential Rural/Metro Ambulance Deployment At Peak Hours

Rural/Metro delivers more patients to Scripps Mercy Hospital in Hillcrest than anywhere else in the city, Johnson said. An ambulance is almost always at the hospital, so the company usually never puts one at fire stations in the neighborhoods surrounding the hospital.

The San Ysidro Port of Entry is the busiest address in the whole city, Johnson said. The ambulance system gets calls from partiers-gone-sick and traffic accidents. Sometimes, Mexican ambulances drive Americans to the border and hand them off to Rural/Metro. The company has as many as three ambulances at one time serving the border and surrounding communities.

The Plan vs. Reality

Predicting the future doesn’t always work.

Some days, Rural/Metro doesn’t have a lot of emergency medical responses. This map from Sept. 10 shows the ambulances that were available throughout the day.  The lower the line, the more ambulances were responding to emergencies.

Sept. 10, 2013 Ambulance Response

Other days, the unexpected happens and the volume looks like it did on Sept. 3.

Sept. 3, 2013 Ambulance Responses

Lately, the picture has been more like the latter.

Over the past 18 months, the ambulance system has seen about a 25 percent spike in usage. Statistics would typically reveal what caused some of those increases, such as flu season or hot weather. But this time, Johnson said, complaints are all over the board, and he can’t tell what’s going on.

“Something happened,” he said.

Johnson speculated that the increase could have something to do with the economy and lack of health coverage. People then use the 911 system as their primary medical care. Ambulance companies around the county are seeing the same boost in numbers, he said.

Rural/Metro has put 1,000 more hours of ambulance coverage on the street a month than it did this time last year to deal with the increase. But it’s still having some trouble.

The company is exceeding its response time goals, but those figures exclude especially busy periods and other exemptions written into its contract. Without those exemptions, the company was responding within 12 minutes to highest-priority emergencies 87 percent of the time, not 90 percent, according to the most recent statistics.

City officials, who discussed response time issues as well as Rural/Metro’s recent bankruptcy at a Wednesday Council committee hearing, said they plan to do away with some of the exemptions in a future ambulance contract. Next month, interim mayor Todd Gloria is expected to have a timeline for when the contract might go out to bid.

The Bottom Line

When the contract does go out to bid, one of the most critical numbers will be the response time target – 12 minutes for highest-level emergencies is a county mandate. Companies, including Rural/Metro, will design their proposals to meet that timeline. The city’s fire union wants the Fire-Rescue Department to develop a plan, too.

Johnson said his company could develop a system that would get ambulances to major emergencies within five minutes instead of 12. But doing so would cost people who end up using the ambulances more money.

“We would build it that way and you’d be paying probably five grand per ambulance trip,” he said.

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Liam Dillon

Liam Dillon

Liam Dillon is senior reporter and assistant editor for Voice of San Diego. He leads VOSD’s investigations and writes about how regular people interact with local government. What should he write about next? Please contact him directly at liam.dillon@voiceofsandiego.org or 619.550.5663.

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10 comments
edwardg
edwardg

It all comes down to money. Ambulance bills are expensive in SD because the program has to be self supporting. R/M gets no city subsidy. They staff their units and buy their equipment with the money they earn from patient transports. Many of their patients have little or no insurance. They cost shift to the insurances just like the rest of health care does; including fire based EMS. Ask what it costs in Sacramento for an ambulance transport by Sac City Fire.. A lot!! The city used to kick in some money and infrastructure (dispatch and fire station housing) to keep things affordable. Now the city pays nothing and demands RENT to house ambulances that serve city residents. There's nothing wrong with profit. This is America. R/M runs a tight ship and works efficiently. Their people are just as dedicated as their SDFR comrades. Profit is the reward for risk. R/M takes on financial risk and liability with they sign the contract. Some years they make money, some years they loose money (see recent bankruptcy). A reasonable return is the reward for efficiency. If SDFR wants to bid and can to the job for less, then more power to them. I doubt they can with the public safety retirement burden they have, but we'll see. I know Javier Mainar, SDFR Chief and I know Wayne Johnson R/M General Manager. They are both 30 year dedicated servants working to provide the best service possible to San Diego.

Marc Davis
Marc Davis subscriber

Wish I had the answer to that one! You are correct.

Creek
Creek

Here's a thought Marc Davis... teach the citizens that 911 is for emergencies ONLY, and not necessarily for every person they see laying on the grass just trying to catch a nap. That in itself should provide immediate relief for an ABUSED paramedic 911 system. For the abusers and lunchtime cell phone heroes, maybe SDPD and SDFR could find a way to hold them accountable for ALL of their false/unwarranted calls. Moneysaver? Moneysaver??

Marc Davis
Marc Davis

Yup it's 5 grand to respond to your emergency or we can't get there in time to save your life!! Stock holders in private companies get paid first then we can get there on time for your family members emergency. Does this make any sense? When did responding to medical emergencies become a profit driven public service? Public safety is not a business that should produce a profit on someones bad day! Public safety services are an insurance program that tax payers pay taxes to so that they can be where you need them when you need them. Not based on peak and non peak time loads. That's bean counter stuff with your loved ones life on the line! I'm a city resident and tax payer and want my public safety services to respond quickly with well trained personnel and equipment to handle the emergency. If counting nickels and graphing peak times seems appropriate, you have never needed life safety services. The next thing we will be asking is to pay the Lifeguard a service fee as you get on the beach or they will not enter the water to save you're drowning child. The fire service did this hundreds of years ago. If you didn't have a proof of fire insurance plaque hanging on the front of your home and it was on fire the fire department would not fight the fire. They would protect the neighbors home that displayed the plaque and was insured while your home burned. Are we willing to turn the clocks back that far to save a dollar? What have our community values become? Sounds like hostage to wall street investors and brokers who by the way were the folks that brought our county down to it's knees a few years ago.

Marc Davis
Marc Davis subscriber

Yup it's 5 grand to respond to your emergency or we can't get there in time to save your life!! Stock holders in private companies get paid first then we can get there on time for your family members emergency. Does this make any sense? When did responding to medical emergencies become a profit driven public service? Public safety is not a business that should produce a profit on someones bad day! Public safety services are an insurance program that tax payers pay taxes to so that they can be where you need them when you need them. Not based on peak and non peak time loads. That's bean counter stuff with your loved ones life on the line! I'm a city resident and tax payer and want my public safety services to respond quickly with well trained personnel and equipment to handle the emergency. If counting nickels and graphing peak times seems appropriate, you have never needed life safety services. The next thing we will be asking is to pay the Lifeguard a service fee as you get on the beach or they will not enter the water to save you're drowning child. The fire service did this hundreds of years ago. If you didn't have a proof of fire insurance plaque hanging on the front of your home and it was on fire the fire department would not fight the fire. They would protect the neighbors home that displayed the plaque and was insured while your home burned. Are we willing to turn the clocks back that far to save a dollar? What have our community values become? Sounds like hostage to wall street investors and brokers who by the way were the folks that brought our county down to it's knees a few years ago.

Marc Davis
Marc Davis

Wish I had the answer to that one! You are correct.

rfp92101
rfp92101

Marc, what fire station do you work at these days? If only the local governments could afford to do it in house... but they can't. It ends up costing tax payers more money. How are those single roles coming along?

High Performance EMS
High Performance EMS

The trouble is EMS services are funded differently from Fire and Police which are mandated services. Ambulances are not. Your home insurance rate is based on the proximity of fire stations/hydrants and crime. It would be a very different picture if your health insurance was based on EMS availability, but its not. So many governments "outsource" this "amenity" while in others the unions see the increase in demand for these services as a way to retain jobs for firefighters whose call volume is actually decreasing. Unfortunately, as long as EMS remains a purely local issue, every city and county across the country will offer a different level of service with various funding mechanisms.

Matt Finish
Matt Finish

Stop typing. Slow down. Breathe. Now, it seems the company is merely trying to run things as efficiently as possible with limited scarce resources. That's a good thing, not a bad thing. It's that dedication to "counting nickels and graphing peak times" as you say that allows the ambulance to be more likely to get to you when you need it.

Matt Finish
Matt Finish subscriber

Stop typing. Slow down. Breathe. Now, it seems the company is merely trying to run things as efficiently as possible with limited scarce resources. That's a good thing, not a bad thing. It's that dedication to "counting nickels and graphing peak times" as you say that allows the ambulance to be more likely to get to you when you need it.