The recent boom in U.S. oil production has meant that more crude oil is traveling by rail in this country than ever before -- and that alarming oil-by-rail accidents are also on the rise. The extent of the crude-by-rail (CBR) boom became crystal clear this week, when the U.S. Energy Information Administration released some nifty maps showing the exponential growth of oil volume traversing the nation's railways. I put those maps in a gif above.

In 2010, the U.S. moved an average of 55,000 oil barrels per day via rail. Last year, the average CBR volume exceeded 1 million barrels per day. Most of that flow comes from the Bakken oilfields in North Dakota, with a smaller amount being pumped out of the Niobrara shale formation in Colorado and Wyoming.

Most of that oil is flowing to refineries on the East and Gulf Coasts. Communities on those rail lines are starting to take note of the high volumes of crude rumbling through town, particularly in the wake of a few recent high-profile explosions.

It's worth keeping in mind that both railways and pipelines deliver well over 99 percent of their crude oil safely and without incident. But due to the sheer volume now moving across the country in one form or another, accidents are inevitable. The rapid growth of that volume, illustrated in the maps above, is another contributing factor.