Back before the 1840s, many barges in the United States were dragged along canals by mules or horses walking along the bank. This wasn't a bad way of transporting cargo—the mules could carry ten times as much weight as they could hauling a cart on the road—but the method quickly became obsolete once railroads showed up.

But now Kris De Decker has a fascinating, history-heavy piece in Low-Tech Magazine (oh yes) suggesting that if oil prices keep rising, or as energy conservation becomes increasingly important, the "trolleyboat" could make a comeback. Canal transport is already a far more efficient way to transport goods than train or truck, and it'd be more efficient still if the boats were dragged along by land rather than powered by propellers. The barges wouldn't use mules, of course—they'd be pulled by some sort of electric train running along the canal bank. (This'd be similar to the "mules" used in the Panama Canal to move ships into the locks; see the pic.) The end result would be a stunning ten times more energy-efficient than truck transport.

Still, this all seems a little fantastical: Canal transport is awfully sluggish (that's why they were beat out by railroads in the first place), and you need plenty of water to maintain the canals, which could pose a problem in our hotter, drier future. If fuel prices do keep rising and we do cap carbon emissions, the most likely freight change we'd see is a shift from trucks to electrified rail—a move that would still produce big energy savings without the downsides. Odds are it would take a pretty dystopian peak-oil scenario before canal transport made a massive comeback (same goes for other low-tech—but super-efficient—transport alternatives like the dirigible).

(Flickr photo credit: WenDem)