Buses and Motorcoaches: The Steel Wave

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.

Perception, Misunderstanding and Illusion

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:

• When the light turned green, a bicyclist lined up with the front of the bus at the intersection watched a schoolbus next to it pull forward into the intersection. Just before the bus' front cap reached the halfway point - from which the driver would then have turned sharply to the right - the bicyclist assumed that the vehicle would be traveling straight through the intersection, and entered the roadway alongside it.. Because bicycles can initially accelerate more rapidly than buses, the cyclist reached the mid-point of the bus barely before the bus began to turn. Suddenly its huge body swung sharply to the right, like "steel wave" moving toward the cyclist alongside the bus. The rider and his bicycle were knocked down and crushed by the curb-side rear tires of the bus.
• Discharging his passengers at a rest stop, a motorcoach driver told them to return in 30 minutes and, turning right minutes later, pulled out toward the fueling station housed just around the corner. When a non-English-speaking passenger saw the bus pull out, she thought she was being stranded, and began to chase the bus as it accelerated. Running alongside the coach and pounding on it with her left fist, she actually caught up with the front plane of the coach and, momentarily, stepped in front of it - just as it began its sharp right turn. Failing to check his curb-side, exterior rear-view mirror, the driver began turning right, the "Steel Wave" knocked her down, and she was crushed the coach's curb-side, front tire.
• A transit bus failed to stop at either the limit line (crosswalk) or in the middle of the intersection as it pulled into it and, without hesitation, began turning left at 25 mph. An oncoming motorist who assumed the bus was proceeding straight through the intersection, and who similarly attended to travel straight through the intersection, was caught in the amber light at the last minute and, seeing the huge bus veer in front of it (@ 25 mph, no less) that motorist managed to slam on his car's brakes at the last moment and avoid colliding with it. A motorcyclist a few meters further ahead of this car was not so lucky, and was practically struck by the front of the bus head-on. Instead, he veered sharply to the left - presumably hoping to pass behind the rear of the bus as it moved forward - but unable to completely clear the bus, crashed into its curb-side rear door, killing the passenger riding on his cycle's "crotch rocket," and severely injuring himself. The bus driver actually made seven errors in fewer seconds.

Perception, Positioning and Responsibility

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.