Older data recorders provide limited information on ambulance crash
Police investigators are still asking questions, checking clues and looking for the cause of a weekend accident that killed two Indianapolis EMS workers.
A passenger car struck an ambulance, knocking it on its side and into the path of a parked SUV.
Many people have asked how a small car can send an ambulance twice its weight rolling over and out of control into a deadly collision. It's easier than you might imagine.
"It happens, not frequently, but more frequently than you would think," said James Casassa, an engineer with Wolf Technical Services.
A car-ambulance collision in Philadelphia in March 2012 looks very similar to what investigators describe happening in Indianapolis last Saturday morning. A security camera caught the accident. An ambulance traveling through an intersection is hit on the rear side by a passenger car. It turns sideways.
"The larger vehicle, with the larger center of gravity, meaning it is taller, basically is more prone to turn over," explained Casassa.
In the Philadelphia crash, the ambulance landed on its side and slid down the street. The two paramedics inside had non-life-threatening injuries.
James Casassa and Wolf Technical Services use computer analysis to recreate the circumstances of accidents. Like police, they use skid marks, damage assessments, road conditions and other clues.
"In most cases you are looking at, in a good analysis, two to three miles an hour of the actual speeds," said Casassa.
In this case, investigators are working without the benefit of an event data recorder. It collects and saves a few seconds of a vehicle's operating systems prior to an accident.
The computer systems today's cars and trucks can't run without also have a short memory. They keep just a few critical seconds of information that can be a treasure trove to investigators what happened and how an accident occurred.
The government estimates more than 90 percent of new cars are recording speed, acceleration, braking, even seat belt use.
The vehicles in Saturday's crash are more than ten years old and their data recorders are rudimentary. Information they may contain is inaccessible to investigators.
A lot happens in the five seconds before an accident. Without that computer data, investigators may not be able to determine whether the vehicles were accelerating, coasting, slowing, breaking, trying to avoid the accident, or perhaps never saw the collision coming.
New federal regulations say cars equipped with data recorders must measure at least 15 specific functions and make that data easier for investigators access and decipher.