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Originally Posted by ddvmke
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It's not really unproven. This is called a "guided bus," "tram bus," or some variation thereof. There are a few of them around the world. I trekked out to a Paris suburb just to
see an especially good one the last time I was there.
Anyway there are three things to unpack here:
1. The bus that looks a lot like a streetcar.
Certainly it's possible to make buses look more like trams. But there are some limiting factors:
a. You can't do it if the bus comes into close near-contact with cars at any point along its route. Consider what's missing from that
Chinese bus/tram: bumpers and rear-view mirrors. The Colfax BRT, even the new-and-better one, will need those things for safety reasons, and therefore will not be able to mask its bus-ness as much. This is a major problem because fully separating the busway enough to make this practical is both politically challenging and wipes out a lot of the cost savings from doing BRT to begin with.
b. In the United States it is illegal to operate a bus longer than around 60'. This is probably something that could be overcome if anyone cared to try, but it is nonetheless a difficulty.
c. Even under the best circumstances, there would still be differences in ride quality, which is a bigger deal than it generally gets credit for.
2. The automated guideway.
See the dashed lines on the road in the Chinese link? The bus drives itself (or in some cases partially drives itself) by having a laser track that line. There are some benefits to this, most importantly at stations where you're trying to achieve a consistent level entry.
There is one city in the US that uses a laser-guided bus: Las Vegas, along its MAX BRT line. You can see the dashed lines in
this photo, and the guiding laser protruding from the front of the bus frame in
this photo.
Know the problem? The laser has to be able to clearly see the dashed lines in order for it to work. No big deal in sunny Las Vegas, but impractical in snowy Denver.
As autonomous vehicle technology gets better we can probably assume driverless buses on major big city routes will eventually become a thing. But so far we still have to use tricks like this, and they're not always practical.
3. The zero-emissions.
As TakeFive said, there are indeed buses that can do this coming online now. In fact
we have them in DC running on city streets right now. There is also perfectly good
trolleybus technology that does the same thing but requires wires. And I do absolutely expect to see more and more US cities using these in the near future. Denver certainly could.
But they too have some problems:
a. They're noticably more expensive up front. You do save money on gas, but it's hard to take the capital hit on your bus-buying budget. You don't want to end up with fewer buses.
b. They're not actually zero emissions. There are still emissions from the electricity being generated, wherever that happens. God help you if it's a coal plant. They're merely zero emissions at the point of the vehicle.
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