As an asset class, railways have a worrying history. Railway mania in Britain in the 1840s left plenty of unwary investors nursing hefty losses; that episode sits in most lists of history's biggest speculative bubbles. But the prices of shares and bonds are dauntingly high, which has stoked interest in all manner of outlandish "alternative" assets in recent years. That, along with legal changes making it easier to repossess collateral that goes clickety-clack, may soon have investors funnelling cash into locomotives, carriages and goods wagons again.