Years ago we showed you this concept for an elevated, tunnel-like bus that would not interfere with ordinary road traffic:
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Conceived of in China by engineer Song Youzhou, the concept was unveiled in 2010 and scuttled thereafter for being unworkable. But now Song is attempting to resuscitate the project, and the blogosphere has been gamely playing along, circulating this video from 2012:
As rendered, what you're seeing in the video is physically impossible. The issue is one of turning radius. If you've ever seen a limousine, a city bus or a tractor trailer try to get around a corner on your average city block, the problem becomes obvious.
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You have what's known as the actual radius versus the effective radius, which is to say, when a long-wheelbased vehicle makes a turn, there comes a point at which the midpoint of the wheelbase is cutting a radius different from the arc that the wheels are describing. This presents a problem if there are vehicles, or guardrails, alongside the vehicle.
In short, it would be impossible for Song's vehicle to navigate the impossibly-tight radii depicted in the video. Take a look, for instance, at these stills:
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In those shots, you can clearly see he's got the vehicle bending, as if it's made of rubber rather than steel.
This physics problem means that the vehicle either needs to be articulated every few feet along its length, or have articulating points with an extreme differential where the carriages meet. That will be tricky to execute given the vehicle's width--at seven meters it is nearly three times as wide as your average 2.5-meter-wide articulating bus--but not impossible to accomplish. Indeed, at the Beijing International High-Tech Expo, where Song presented a working scale model earlier this month, he has opted for the latter approach:
In those final frames you can see the extremely sweeping radius--far wider than what's depicted in the first video--required to get the concept to work. If roads are built to accommodate in a wide-avenue city like Beijing, the concept ought to be workable. But it's unlikely to be suited for anything other than straight-line travel in a city riddled with your average right-angle intersections.