31 July 2015

Automobile Safety v. Airline Safety

It is common place to compare the way automobile manufacturers and airplane manufacturers treat accidents.  Automobile manufacturers often blame the drivers or argue that "shit happens" and don't systemically analyze every accident to prevent it from happening again.  Airplane manufacturers assume that every accident is due to a defect in the product, and rigorously investigate and analyze each accident so it can never happen again.

The analogy if sometimes applied to how hospitals handle bad outcomes, in an effort to cajole the medical establishment to start acting like airplane manufacturers, so that they can establish good systems to prevent mistakes, and in that context, the analogy is fair.

But, the analogy is not really fair to automobile manufacturers.  Why?

1.  Commercial airline accidents are overwhelmingly single vehicle accidents due to the air traffic control system.  Automobile accidents are overwhelmingly collisions with other vehicles or at least caused by avoidance maneuvers conducted to avoid collisions with other vehicles, and it really isn't viable to institute the equivalent of an air traffic control system for automobiles.

The airline industry's experience may argue strongly for the institution of the equivalent of an air traffic control system for ships in harbors.  But, it is inherently easier to engineer solutions to problems caused by single vehicle accidents than to problems caused by collisions or near collisions which are a problem with the entire traffic management system, and not so much with the vehicle itself.  Likewise, when a commercial airline crashes in the absence of a collision, the likelihood that a defective airplane was at issue is great.

Notably, while most airplane accidents are carefully investigated and result in soul searching by the manufacturers looking for a solution, this did not happen in the same way rebels in Ukraine shot down a Malaysian airliner with a ground to air missile.

2. Good systems are only half of the reason that commercial airline accidents are so rare.  The other is that commercial airlines are flown by professional pilots who are on the job, rather than by amateurs.  The fair analogy in terms of safety to a commercial airliner is not the accident rate of private automobiles, but the accident rate of buses, which is much, much lower than the accident rate of private automobiles.

If one wants to control for this factor one should compare the accident rates for general aviation aircraft not flown by professional charter pilots against the accident rate for motor vehicles not driven by professional drivers who are on the job.  Accident rates for general aviation aircraft not flown by professional charter pilots turn out to be much higher and are actually quite similar to the accident rates for private motor vehicles driven by amateurs.

Operator error accounts for a much larger share of general aviation accidents than it does of commercial airline accidents, and also accounts for a much larger share of accidents by ordinary amateur automobile operators than it does of accidents by professional bus drivers.

For example, a very substantial share of all motor vehicle accidents involve drunk drivers.  But, very few bus accidents involve drunk bus drivers.  Similarly, many motor vehicle accidents are caused by inexperienced and reckless teenage drivers acting carelessly or recklessly, while very few bus accidents are caused by bus drivers acting in this fashion.

3. It is also notable the general aviation aircraft and commercial airlines tend to fly out of different airports and in different airspace.  Commercial airlines tend to cruise at higher altitudes and operate out of major commercial airports, while general aviation aircraft tend to cruise at lower altitudes and operate out of smaller local airports.  Thus, commercial airliners are largely insulated from interactions with less safely piloted general aviation aircraft, while motor vehicles overwhelmingly share the same roads, without regard to who is operating them.

4. It is notable that a very share share of all on the job fatalities involve motor vehicle accidents, crimes and suicides.  Each of these, unlike most other job fatalities, has as a substantial cause, actions of people who are not within the control of the employer and frequently conduct at locations that are not within the control of the employer.  Solving these causes of on the job fatalities requires societal level solutions and not employer level solutions, unlike most other potential causes of on the job fatalities and injuries.

Now, this isn't to say that the analogy of hospitals to airlines is unfair.  Hospitals, like commercial airliners, are operated by on the job professionals.  Bad outcomes in hospitals, like single plane accidents by commercial airliners, operate in environments that are controlled by a single party with the power to change the systems that cause them.

But, automobile accidents, unlike accidents involving commercial airliners, do not predominantly involve single vehicle accidents in vehicles operated by expert on the job operators, so the analogy in that case of automobile manufacturers to airline manufacturers is really unfair.  Automobile manufacturers are reasonable good (although not as good as airlines) at investigating and resolving single vehicle accidents in vehicles where there is good cause to believe that a reckless operator was not the problem, which is really the only fair apples to apples comparison in this case.

1 comment:

kyle said...

As a professional pilot I would like to comment on a few things. First, when an aviation accident happens, it is initially looked at as neither pilot error or malfunction but both until one is singled out. It is almost always pilot error in aviation accidents, while malfunctions do cause accidents, engineering has became so remarkably well on modern aircraft and the system redundancy built into these airplanes has greatly helped reduced malfunctions a good deal. Not to mention pilot training for emergencies has gotten a lot better over the past few years. But in the end, pilot error is still the cause of almost double the accidents than malfunctions/emergencies. Second, interestingly enough I know several professional pilots who have taken jobs in the medical sector to train hospitals for emergencies. The aviation industry has developed some of the best simulators in the world, airline simulators are million dollar machines that are identical to a real aircraft. So pilot training and emergency scenario training has gotten massively better. Those pilots use that approach in the medical field, they go to hospitals and simulate real world medical emergencies with the upmost realism and train the staff in those simulations. It helps reduce patient death and lawsuits, using simulations like the airlines do has become a very useful tool for hospitals.