Something one rarely ever finds in a professional driver’s training materials is an explanation of inertial and centrifugal forces. These forces were rudiments of science hundreds of years ago. They can have extraordinary impacts on the movement of both passengers and freight. Yet few public transportation agencies or companies even acknowledge their existence, much less explain what they can do to passengers.
Certain industry standards — like not letting passengers ride while standing forward of the white line — were created to combat the worst risks of centrifugal force. During a left turn, a passenger standing forward of this line could be pitched down the front stepwell, and likely blast open the just-closed door. Moments later, he or she could be crushed when the bus’ rear axle rolls over this passenger. In contrast, few transit or motorcoach agencies or companies seem to care about lesser risks — like passengers flying rearward as the vehicle pulls away from the stop, or flying forward as it decelerates and brakes.
Because inertial and centrifugal forces can be so forceful, passengers must ride fully seated in most modes. Even among the worse schoolbus services, pulling away before a passenger is fully-seated is a taboo. So too is allowing a student to arise from his or her seat before the bus comes to a complete stop. It is similarly rare for a paratransit, NEMT vehicle, limousine or taxi to move before its passengers are seated (although not-securing wheelchairs is a rampant deviation in the paratransit and NEMT sectors). In contrast, racing away from the stop before a just-boarded passenger reaches a seat or stanchion is commonplace in transit service — particularly in large urban areas where all or most schedules are tight even with scores of this violation committed on every run. And while allowing passengers to reach a seat is adhered to in most motorcoach services, it is often not observed when such vehicles are deployed by transit agencies. The consequences are even more acute on motorcoaches because, unlike transit buses, they do not even contain stanchions.
Even on transit buses which contain stanchions, these fixtures are designed and intended for passengers to hold onto, with both feet firmly planted on the floor, while the vehicle is moving. They are not designed or intended for navigating to one’s seat while the bus is accelerating, like an adult-sized jungle gym. Similarly, they are not designed for navigating from one’s seat to a nearby exit door while the bus is decelerating or braking to a stop.
Inertial and Centrifugal Forces: The Fundamentals
In oversimplified technical terms:
- Inertial forces impact passengers as the vehicle they are riding on moves longitudinally. As the vehicle accelerates, passengers move rearward. As it decelerates or brakes, they move forward. All things equal, the higher the rate of acceleration or deceleration, the greater the forces.
- Centrifugal forces impact passengers as the vehicle moves laterally — switching lanes, pulling angularly away from bus stops, and turning or cornering. All things equal, the greater the speed with respect to the arc of the turn (or any lateral movement), the greater the forces.
Of course, all things are rarely equal. Among the most important variables, the better the suspension system, the more these forces are “dampened.” So in schoolbuses (constructed on truck-like “leaf-spring” suspension systems), seating the passengers before the vehicle moves is even more important than it is in a motorcoach or transit bus (constructed on a pneumatic suspension system with at least one “air bag” at most wheel positions). Similarly, the van- and minibus conversions deployed in paratransit, NEMT and special education services have mostly coil-like suspension systems on the front axle, and (usually) leaf-springs on the rear axle.
Frankly, riding as a standee on any vehicle — even one with a pneumatic suspension system — is significantly (if not exponentially) more dangerous than riding in a seat. But riding as a standee on a body-on-chassis vehicle with a spring suspension system involves an extraordinary risk. TA President Ned Einstein once served as an expert witness on case where a spring-suspension bus was deployed in transit service. Before the bus completed its left turn from a dead stop, three passengers were tossed through a closed door into the roadway. Two were standees. The third was seated on the opposing side of the aisle from the door (see “The Mysterious Force“)!
Extremes of Inertial and Centrifugal Force
The extremes of inertial force are best illustrated by a collision. When the impact forces or “closing speeds” (the combined speeds of two vehicles travelling in different directions at the moment they collide) reach 30 mph, this speed creates 20 g-forces. Seatbelts and wheelchair securement hardware is certified to withstand this level of g-forces.
In even the most poorly-constructed forward-facing seat, the occupant usually has a seat back of some sort in front of him or her. And that seat is welded or bolted to the floor. So one needs little imagination to understand how a standee would fare in such a collision. Similarly, it should be obvious why a wheelchair should be firmly secured — much less secured at all four wheel positions, which is the irrefutable industry standard and the strong recommendation of all legitimate securement manufacturers.
The extremes of centrifugal force are illustrated by a rollover. There is a limit to how fast any object can turn or pivot around a given arc or curve. When the object exceeds this speed, one side of it — the tires and wheels of a vehicle — literally leave the ground. Most vehicles are designed to return to a horizontal plane (i.e., the roadway surface) from even a severe angle. For example, most buses or coaches will return to the ground from a “tilt” of about 28 degrees when simply tilted and not moving longitudinally. But once this tilt is exceeded, or this angle is approached too quickly (i.e., from the vehicle’s forward movement), the vehicle will roll over. In many catastrophic accidents (most commonly involving motorcoaches whose drivers have fallen asleep at the wheel), the vehicle may tumble completely around (i.e., a 360-degree rotation) over and over again — particularly when it rolls down a hill. But merely accelerating too quickly on a mild turn can pitch passengers through a closed door and out of the bus (see The Mysterious Force). And in lateral movements that do not even approach a rollover, passengers can be ejected through windows. Few ejectees survive.
Only in fixed route transit or some passenger rail modes (e.g., subways) are passengers permitted to ride standing. True “integrally-constructed” transit buses contain pneumatic suspension systems. “Heavy rail” passenger trains contain heavy-duty suspension systems — even while rail vehicles experience little pitch (picture a roller coaster) or yaw (picture a surfer). Yet even with their superior suspension systems, the interiors of these vehicles are outfitted with horizontal and vertical stanchions, intended for passengers to hold onto while standing on both feet. As noted, these devices are not designed for navigating between a door and some position within the passenger compartment.
When a bus pulls into or away from a stop, it moves both laterally (exerting centrifugal forces on the passengers) and longitudinally (exerting inertial forces on the passengers):
- During acceleration, the greatest exertion of these forces occurs when the vehicle travels from a complete stop to the next, tiniest increment of speed.
- During deceleration or braking, the greatest exertion of these forces occurs when the vehicle goes from its slowest, declining crawl to a complete stop.
Both of these moments are illustrated by the “lurch” passengers feel — no matter how quickly the vehicle accelerates or how slowly it decelerates or brakes. Mathematically, this change is displayed as X/Y = ∞. This phenomenon explains why a passenger is knocked down as a bus or coach pulls away from a stop before he or she reaches a seat (or a “point of securement” on a transit bus) even if it accelerates slowly and gently. And it explains why a passenger walking toward or waiting near an exit can be knocked down as the vehicle crawls to a stop. It is utter nonsense to claim that the vehicle accelerated too quickly or braked too sharply. The greatest exertion of these forces occurs when the vehicle’s speed (in any direction) goes from nothing to anything, or from anything to nothing.
For this reason, no bus should pull away from a stop until every boarding passenger has reached a seat (or a stanchion in a transit bus). Similarly, passengers should be conditioned, through persistent warnings, to not arise from their seats before their vehicles come to a complete halt at their selected stops. Plenty of transit agencies contain rules about this procedure for boarding. Yet few mention it for alighting — even though the same principle is involved as in boarding. Regardless, the schedules of many transit agencies’ routes (and all of many transit agencies’ routes) are so tight that this safety compromise is made at virtually every stop.
Most interesting is the fact that even with scores or hundreds of these compromises on many runs of a transit route, the buses still arrive at the end of the route late. Because transit passengers are allowed to board only at the front door, they are encouraged (often with signage) to exit from the rear. So consistent with this practice, many boarding passengers target seats or stanchions in the middle or rear of the bus. This small trek can easily take a young adult with good balance 10 or 15 seconds. And on a busy run, a driver can make this safety compromise scores of times. So with this stunt, high ridership and multiple stops, a driver can easily “shave” a good 10 minutes off his or her “running time.” For this reason, violating this principle and industry-standard procedure is, by far, the most common safety compromise.
Violating this principle and industry-standard procedure is, by far, the most common safety compromise.
Troubling, of course, is that this violation is routinely committed by drivers even on systems which formally forbid it as a policy matter. More interesting, even on systems where every route’s schedule is tight, and where all drivers regularly commit this safety compromise (scores of times every run), the vehicles still reach their destinations behind schedule! In at least a dozen ride-and-time exercises conducted by TA President Ned Einstein, some transit systems’ routes fall 20 to 30 minutes behind schedule (when the entire route was only 90 minutes long, or less) even with considerable time “shaved” off regularly committing this single safety compromise.
A driver can create a considerable chunk of “recovery time” by not letting most of a run’s 50 to 100 passengers reach a seat or stanchion.
As a footnote for plaintiffs’ attorneys, the General Manager or Executive Director of every transit agency knows (or should know) which routes’ schedules are too tight. So lawsuits involving on-board slip-and-falls (particularly after boarding and before alighting) are not respondeat superior cases. They involve negligent policy-making and negligent scheduling. And they involve reckless disregard.
As noted, drivers of three of the four motorcoach “sectors” deploying motorcoach vehicles rarely pull this stunt: Charter service, tour service, and the better intercity/scheduled services. In contrast, many drivers of motorcoach services deployed by (or operating under contract to transit agencies — mostly in commuter/express mode) regularly follow dangerous transit practices and make this safety compromise.
In every transit system, policies, procedures and training contain the mantra “Safety Comes First, when evidence is examined, it is clear that reliability (schedule adherence or on-time performance) and customer service are the genuine priorities, despite the policy and procedural subterfuge to obfuscate the truth.
Worse Still with Motorcoaches
Motorcoaches are deployed in basically four sectors: tour service, charter service, intercity/scheduled service and commuter/express service — the latter provided by transit agencies or private companies under contract to these agencies. On-board slip-and-falls are rare to passengers traveling on the first three of these sectors. In contrast, they are common to motorcoaches deployed, by transit agencies (or their contractors) in commuter/express service.
As with most safety compromises, this problem is largely the result of schedules being too tight. However, this problem is compounded on motorcoaches because they are not equipped with horizontal or vertical stanchions. Of course, even if they were, these appendages are not designed for navigation purposes. Nonetheless, without these appendages, motorcoach passengers must reach a seat before the coach moves.
Again, because of tight schedules, drivers of commuter/express service rarely let a passenger reach a seat, after boarding, before pulling away from the stop. Equally of interest, these drivers rarely (if ever) warn passengers to remain in their seats as the vehicles approach their stops. The few exceptions usually occur at major facilities like bus terminals and park-and-ride lots, where large numbers of passengers board and alight, and some stow or retrieve luggage, packages, strollers or bicycles from the luggage bays. Some passengers eventually learn that the “dwell time” at these stops is likely to be much longer than at intermediate stops – and thus remain in their seats as the coach is pulling into these stops. Yet even at most of these major stops, motorcoach drivers providing intercity/scheduled service often pull away when the last boarding passenger has either stepped onto the floor level (from the stepwell beneath it), or in some cases, when that passenger has walked behind the white line — yet still not reached a seat. Occasionally, drivers will pull out simply after a passenger has stepped onto the bottom step of the stepwell, just inside the door.
Also, while most intercity/scheduled service drivers follow these rules, all do not. As a practical reality, it is sometimes difficult to even discern between a motorcoach providing intercity service versus commuter/express service, because some commuter/express travel times can be several hours long. Regardless, the closer intercity/scheduled service begins to resemble commuter/express service, the less likely drivers are to ensure that their passengers reach a seat before pulling away. And the less likely they will be to instruct their passengers (periodically) to remain in their seats until the vehicles come to a complete stop.
Rapid Acceleration, Deceleration and Braking
Sharp braking into a bus stop, or racing away from one, can shave a few seconds from a route’s running time. But like most safety compromises that shave only a few seconds, committing this type of safety compromise can occur dozens or scores of times on a single run of a transit bus or motorcoach deployed in commuter/express service. So in the process of multiple safety compromises of this type, a driver can shave several minutes off a route’s running time.
If every passenger were fully seated when either of these scenarios occurs (or on a transit bus, at least holding onto a vertical or horizontal stanchion), these compromises would not have such serious consequences. Nor would wheelchairs tip over as often, or passengers fly out of their seats. More interestingly, the industry standard, on any type of wheelchair-accessible vehicle, is for a three-point occupant restraint system to be used to secure wheelchair users into their chairs. In fact, the installation of such devices is a Federal regulatory requirement. Thus, if a wheelchair user is injured as a result of this device being missing, his or her civil rights have been violated.
The failure to install a three-point occupant restraint system at every wheelchair securement position translates, automatically, into a civil rights violation whenever such a passenger is injured as a result.
As a curious legal matter, the time and money saved by operators whose drivers do not follow these rules grossly exceeds the damage awards and settlements of those injured as a result of these omissions. But this is largely because many of the victims’ attorneys do not know how to prosecute such cases. Or their corporate culture is to do more cases less thoroughly — effectively making money “by volume.”
Otherwise, when basic things are understood, on-board slip-and-fall cases are downhill. The most important fundamentals for this dynamic is an understanding of inertial and centrifugal forces. As noted:
- A vehicles’ greatest moment of acceleration is its first nanosecond of movement.
- A vehicle’s greatest moment of deceleration or braking is its last nanosecond of movement.
Further Legal Ramifications
Success in an on-board slip-and-fall case is largely contingent on the plaintiff’s expert understanding the causes that usually lead to this safety compromise (i.e., moving the bus before boarding passengers can reach a seat or stanchion, and failing to warn them to not arise until it comes to a stop). Among the main cause — as with most safety compromises — is a tight schedule. So when an expert implores his attorney to let him or her “ride-and-time” the route, this request is not superfluous. It is the means of discovering the underlying causation of the incident. And as with other safety compromises — almost all of which are designed to create or expand a driver’s recovery time (usually on a route whose schedule cannot be met without such compromises) — the specter of injunctive relief is a large and frightening one. Even the addition of a single bus to a route creates a “template” for every other plaintiff’s counsel in the service area to use whenever his or her client is injured. This is because one half of public transportation-related incidents are a direct result of one or more safety compromises. And most of them are the result of a tight schedule.
The vast majority of safety compromises is the result of a tight schedule.
The most curious thing about all this is the widespread reluctance of attorneys to employ this powerful tool. Transportation Alternatives President Ned Einstein was once involved in an incident where a wheelchair user working as a courier needed to use every route in one transit system’s service area. When one of his buses stopped short, he merely bumped his head on the passenger seated in front of him. The authentic damages were worth perhaps $1000. But drivers of his transit system never secured the plaintiffs’ wheelchair. He desperately needed his poverty-level job, used every bus in the entire system, and feared for his life. Riding and timing five of that system’s routes, Mr. Einstein found all five of them to be tight. His counsel amended the Complaint to ask the judge to instruct the defendant to add another 15% more buses to its system, spreading them out among all the routes, all of whose schedules, again, were too tight. For the plaintiff’s counsel to take that demand off the table, the defendant forked over $170,000, hired a full-time ADA coordinator, retrofitted every one of hundreds of buses with broken, obsolete or otherwise compromised wheelchair securement equipment with brand new, state-of-the-art hardware, and agreed to every other item on a 1 1/2-page list of demands. Legal remedies are nothing if not underused.
Legal remedies are nothing if not underused.
Of course, this tale is peanuts to what can sometimes be accomplished with injunctive relief. In Bus Riders Union v. Los Angeles County Metropolitan Transportation Authority (1999), a class action lawsuit where no one was injured, the judge ordered the defendant to purchase an additional 3,200 buses.