"At a per-passenger-mile basis, rail is about three times as efficient as travel by car, in terms of fuel efficiency, and six times as efficient as travel by air, so there are pretty substantial pollution reduction benefits both in terms of greenhouse gases and other pollutants."

VOA: standard.2010.02.15

Although there would be little direct competition for business between operators, their performance--in reducing costs per passenger mile, say--would provide information that a regulator could use when setting price caps.

ECONOMIST: The end of the tunnel

In the meantime, the number that really matters--called the "yield, " or the price a passenger pays to fly one mile--fell 4.5%.

FORBES: Frontier Airlines Braces For Turbulence

Its cost per passenger mile was around one-third less than its rivals.

ECONOMIST: A hulking beast joins the dogfight