Boxers or Briefs?

The press has been giving a lot of attention to a CDC report that came out last week on motorcycle helmets and fatalities.  That’s surprising because it contains no news on fatality rates.  It mainly regurgitates the information and positions regularly produced by the National Highway Transportation Administration.  (It does also have cost information, which needs another post.)

What they do get right is that in states with stronger helmet laws, fewer bareheaded riders die.  This connection is true, unsurprising, and meaningless.

A state that requires riders to wear boxer shorts will have fewer brief-clad bikers die than will a state that allows everyone the skivvies of their choice.  If 59% of bikers crash wearing boxers and 59% of the fatalities have them, most people will just say, “Of course.  What did you expect?”  But if only 49% of the dead are wearing them, some will say boxers save lives and should be required gear.  On the other hand, if 69% die in them, they are obviously dangerous and the law should require all to wear tighty-whiteys or ride commando.

The CDC is quick to point out that a certain percent of bikers died without boxers…er…helmets on.  But that is meaningless because they don’t say how many crashed without them.  And they have a good reason for that: they don’t really know.

CDC gets its numbers from the National Highway Traffic Safety Administration, whose Fatality Analysis Reporting System collects data on every fatal traffic accident in the nation.  It does not contain any data on accidents where no one died.  If a biker runs off the road, hits a tree and dies, he’s in the data; if he lives, he’s not included.  There is much data here on what kills people but little on what saves them.  Another database , the General Estimate System, contains a sampling of all accidents, but I haven’t seen it used to calculate these types of numbers.

In Florida, we don’t have to rely on samples.  The FDOT publishes its Crash Facts annually, which summarizes many types of information from the data for every crash in the state.  According to its numbers for cycles and helmets from 1996-2010, cyclists dying with helmets on average 59%.   The number of riders crashing with helmets is, as you’ve probably guessed by now, 59%.

These numbers are meaningful.  They mean that helmets affect fatality rates just as much as skivvies do.