Traffic deaths spike after years of decline.

Even as cars have become safer and smarter than at any time in American history, traffic deaths have spiked in the past two years, reversing a general decline going back nearly a decade. Last year, 40,200 people died on the nation’s roads, up about 14% from two years earlier, when 35,398 died.

The reasons are complex, some of them unavoidable. Economic recovery spurs more recreational driving that’s riskier as people go out on weekends and on vacation, driving on unfamiliar roads. More teenagers, who couldn’t afford to drive during the recession, are back behind the wheel.

Other causes are clearly avoidable. In the past three years, 13 states have raised their speed limits to 70 miles per hour and even 75 on some…