There are plenty of things obvious to almost any adult, motorist or pedestrian about large vehicles. The most obvious is their size and mass. But at the other end of the spectrum lie nuances rarely understood by anyone who has not driven a vehicle with a long wheelbase: The way such a vehicle turns, and the way its tires "track" compared to those of a typical automobile, van or pickup truck. And, of course, the way all this looks to someone unfamiliar with it.
When explaining this phenomenon to non-bus or -truck drivers, I like to illustrate it by using toy buses and cars, rubbing their tires on a stamp pad, and then turning them on a piece of paper. Looking at the ink tracks, one can see from the toy car's turn that the rear tires did almost exactly what its front tires did. In a perfectly round turn, they follow an almost identical path, so that the path of the rear tires is virtually superimposed on the path of the front ones. In comparison, when this is done with a toy bus, the toy bus begins entering "the intersection" as though it is not going to turn at all, but suddenly stops, and pivoting on the rear tires, the front tires are turned sharply to the right or left - while the rear tires are dragged behind them in a diagonal path until the bus has moved forward enough for its rear tires to "fall in" behind. The ink pattern crudely resembles a 30-60 triangle.
This approach to turning is endemic to any vehicle with a long wheelbase, except where the radius of the turn is unusually large, such as a freeway ramp, or an extremely large intersection that can accommodate a large, circular turn from a vehicle of this size. Where this is not the case, the general rule is that the bus, coach or truck driver pulls the vehicle forward until its rear axle lines up with the near-side extended curb-line of the perpendicular roadway, stops (a necessity in most cases so that the driver can carefully gauge the movement of vehicles and pedestrians around him or her), and then "swings" the front of the bus sharply in the direction of the turn, again dragging its rear tires in a diagonal behind it. If the bus or truck, instead, had turned earlier - whether following this approach or even trying to turn like a vehicle with a short wheelbase, the rear tires and the rear of the large vehicle's body would be forced to cross part of the front-most edge of the outgoing lane of the perpendicular street, creating a potential collision with a fellow-vehicle lined up at the "limit line" or crosswalk waiting to proceed after the large vehicle finishes its turning movement. Or worse, this "short-cut" can take out a pedestrian not even in the roadway. In extreme cases, as for example where the side street turned into is extremely narrow, turning prematurely can actually drag the rear tires over the near-side curb at the corner - as it did in a lawsuit in which I was involved a few years ago where it ran over a pedestrian literally standing on the sidewalk at the corner.
A vehicle perpendicular to the large turning vehicle will not encounter a problem with this movement, if proper, unless its driver does something pretty careless - like pulling into the intersection prematurely. Otherwise, the greatest problems occur with motorists, cyclists or pedestrians approaching the turning bus or truck in the oncoming direction. A few examples illustrate the dangers of the failure to understand these principles - and why understanding them must be the responsible of the bus, coach or truck driver:
Viewed from above, a helicopter pilot might not find the paths of these vehicles very curious. But the bus, coach or truck's actions lie far beyond the comprehension of most pedestrians who get to observe this phenomenon only from a single position at the ground level - much less a young child. The reality is that none of them could possibly know the bus, coach or truck driver's intentions. Instead, watching the large vehicle pull straight out into an intersection, most observers would think it was heading straight through it. Only when it is too late, the motorist, cyclist or pedestrian may discover these principles as the curb-side of the bus begins swinging back toward the perpendicular curb, and the Steel Wave begins closing in on the vehicle or pedestrian alongside it or quickly approaching it.
There are plenty "rules of the road" that make collisions like those cited above the fault of the bus, coach or truck driver. However, it is also this driver's fault because of the simple fact that oncoming motorist's cannot be expected to read the bus, coach or truck driver's mind.
Last month's NBT installment, "Overcoming Ambiguity with Exaggeration," provided examples of some inexpensive things that can be added to a bus or coach to provide more clues to a motorist, cyclist or pedestrian's facing this situation - clues about the large vehicle's turning movements about to occur, and the illusions that they otherwise create. In considering these suggestions, it is important to note that such incidents may not be commonplace. But they are also not rare. Most importantly, they can be addressed at many levels, including not only modifications to the bus, coach or truck (I am not speaking of anything radical or costly like shortening its wheelbase), but by proper driver training, monitoring and enforcement of a reasonable and prudent transportation system's drivers.
Ned Einstein is the President of Transportation Alternatives, a passenger transportation and automotive consortium engaged in consulting and forensic accident investigation and analysis (more than 600 cases). Specializes in elderly, disabled, schoolchildren. Mr. Einstein has been qualified as an Expert Witness in accident analysis, testimony and mediation in vehicle and pedestrian accidents involving transit, paratransit, schoolbus, motorcoach, special education, non-emergency medical transportation, taxi, shuttle, child transport systems and services...
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