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On ultralight vehicles vs. large mass transit vehicles

One of the questions raised by the numbers which show that U.S. transit does not compete well on energy-efficiency was how transit can fare so poorly. Our intuition, as well as what we are taught, makes us feel that a shared vehicle must be more efficient than a private vehicle. And indeed a well-shared vehicle certainly is better than a solo driver in one of todays oversized cars and light trucks.

But this is a consequence of many factors, and surprisingly, shared transportation is not an inherent winner. Let’s consider why.

We have tended to build our transit on large, heavy vehicles. This is necessary to have large capacities at rush hour, and to use fewer drivers. But a transit system must serve the public at all times if it is to be effectively. If you ride the transit, you need to know you can get back, and at other than rush hour, without a hugely long wait. The right answer would be to use big vehicles at rush hour and small ones in the off-peak hours, but no transit agency is willing to pay for multiple sets of vehicles. The right answer is to use half-size vehicles twice as often, but again, no agency wants to pay for this or to double the number of drivers. It’s not a cost-effective use of capital or the operating budget, they judge.

Weight

The urban vehicle of the future, as I predict it, is a small, one-person vehicle which resembles a modern electric tricycle with fiberglass shell. It will be fancier than that, with nicer seat, better suspension and other amenities, but chances are it only has to weigh very little. Quite possibly it will weigh less than the passenger — 100 to 200lbs.

Transit vehicles weigh a lot. A city bus comes in around 30,000 lbs. At its average load of 9 passengers, that’s over 3,000lbs of bus per passenger. Even full-up with 60 people (standing room) it’s 500lbs per passenger — better than a modern car with its average of 1.5 people, but still much worse than the ultralight.  read more »