Washington's City Paper responds to this: 

What does it take to get charged with manslaughter when your negligent driving kills someone? Last year the driver of a semi entered a bike lane and killed a Chicago bicyclist. He was issued tickets for driving in a bike lane and failure to take due care with a bicyclist. Why mere tickets instead of a more serious charge? —Alan G. Thomas

With bicyclists on the streets in ever greater numbers—as of 2012, bike commuting was up by 60 percent over the decade prior—incidents like the one you cite (involving the 20-year-old rider Lisa Kuivinen) have predictably become more common. There are now more than 700 bicycle deaths in the U.S. annually and upward of 40,000 injuries, nearly a third of which involve cars—more than any other single factor. The stats for what happens to the party at fault after these collisions are trickier to track. One look at the D.C. region found that less than half of at-fault drivers were prosecuted. In New York City, which sees 10 to 20 cycling deaths each year, motor vehicles caused more than 14,000 pedestrian and cyclist injuries in 2012, but only 101 citations were issued for careless driving. Surely reckless bike behavior was a factor in some cases, but by any estimate, prosecution rates are certainly low, requiring the injured (or the family of the deceased) to bring private criminal complaints or pursue civil suits.

And that’s baked into the system. As a society—one that drives too much, many would argue—we’ve made choices about allocating the risk that ensues when people get behind the wheel. Our traffic laws are basically designed on the assumption that collisions occur even when drivers exercise a reasonable amount of care. Unless one driver clearly hasn’t done this, the state generally opts not to pursue a criminal conviction, leaving the parties to duke it out in court themselves. And gauging negligence—legally, the failure to take reasonable care—is a slippery matter. Just as driving laws vary by state, so too do definitions of negligence (thanks a bunch, federalism). This isn’t a law school torts lecture, though, so let's just say there are differing degrees of it, and at the tippy top is criminal negligence, what you'd have to show to support a charge of vehicular homicide.

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http://www.washingtoncitypaper.com/columns/straight-dope/article/20...