Why doesn't my new motorcoach have seat belts?

A White Paper from the United Motorcoach Association, February 1999

We're happy you asked. It's one of the most prevalent questions in the American bus and luxury motorcoach business today. Indeed, the answer is just as straightforward. As a service to its more than 1,000 member companies, the United Motorcoach Association (UMA) has prepared this brief summary of the answer and the issues surrounding the installation and use of seat belts on coaches.

The answer
We won't keep you in suspense. The quick answer is, "Because they aren't needed." That's not just our answer. It's the answer which is offered by the ***National Transportation Safety Board (NTSB), the Federal Highway Administration (FHWA) and the agency charged with vehicular safety and construction standards, the National Highway Traffic Safety Administration (NHTSA). NHTSA is the federal agency, by the way, which commonly uses a small graphic image of a safety belt at the foot of its own letterhead which says "SAFETY BELTS SAVE LIVES." It's on their letter of August 19, 1992, in which they respond to the common inquiry by saying,

"NHTSA expressly determined that there is not a safety need for safety belts or another type of occupant crash protection at these seating positions (aboard commercial buses weighing more than 10,000 pounds)."

That message has been consistent. As late as December 1998, NHTSA spokespersons have repeated their belief that large buses simply wouldn't reap a safety benefit by placing seat belts throughout the seating compartment.

While the answer is quick and easy, understanding it -- especially in an era when "Buckle Up!" is a universal and enduring campaign cry for millions of automobile motorists -- is the tough part. To understand how federal safety experts can suggest belts are the answer for everyone except motorcoach passengers, we need to go back to some of the lessons you probably forgot 20 minutes after your last high school physics exam. And we need to look at the basic construction of a modern motorcoach, rather than rely on what you already know about the Buick or Honda you might see on the road today.

Before we begin, we should also offer one important observation: the commercial motorcoach of today is the safest form of highway transportation available, bar none. By NTSB's own count, an average of six coach passengers are fatally injured each year over the 30-year span from 1968 to 1998. Compare that to highway death tolls ranging from 30,000 to 50,000 automobile passengers annually, and we're faced with a basic question, "What problem would seat belts on coaches fix?" More on that later. First, the science refresher.

What happens in a crash?
Please note that we, like the regulators and enforcement community, use the word "crash" to describe vehicle collisions. While "accident" is the more common term for most of us, it suggests that the collision happens virtually without avoidable cause. "Crash" makes no such judgement, it simply describes the event.

In any vehicular crash, there are really three collisions taking place. The first is the impact of the vehicle against something else, a wall, another vehicle, a bridge, etc., which causes a rapid "deceleration impulse." The second collision is the impact of the person inside the vehicle against whatever object is there to stop him or her: a steering column, a windshield, a belt or harness. The third collision is within the passenger, when organs slam against bones or other organs, causing most of the actual injuries.

This is where we offer the high school physics refresher. Sir Isaac Newton explained with his laws of physics that passengers will tend to keep going forward when a vehicle stops suddenly. But those laws also help us understand that there are vastly different forces at work when large and small objects collide with something or with one another. It's apparent (and common knowledge) that when a large object and a small object collide, the larger object wins. What is less apparent, though, is the fact that the "G-forces" (one "G" is the force of gravity) exerted on the large object during that rapid deceleration are far less than those in the smaller object. A crash which exerts a 20-G force on an 4,000 pound automobile would exert less than a 7-G force on a 38,000 pound motorcoach.

Seat belts, air bags and harnesses in automobiles are designed to accomplish one primary objective: to hold the passenger and the vehicle tightly together so that they react as a single object. That allows the much smaller passenger to take advantage of the much greater weight of the vehicle they're riding in to reduce the G-forces at work on his or her body during impact. Today's NHTSA load rating requirement for automobile seat belts is 20-G's.

Now the construction part
Today's motorcoaches aren't required to have seat belts. That's because regulators and highway safety experts have long recognized that existing bus design features work extremely well in protecting passengers from the vast majority of crash circumstances.

First, passengers are "made part of the vehicle" in a motorcoach by the seating system's inherent ability to achieve "compartmentalization." What belts accomplish in autos, compartmentalization accomplishes in today's motorcoach: it keeps the passenger "contained" during crashes, like eggs in a carton. Passengers' forward movement is severely limited by the seat ahead of them. In the most common form of motorcoach crash -- head-on or sideswipe -- passengers essentially remain in the seated posture, striking the energy-absorbing, high-back seat ahead of them. The force of the crash is spread over their entire upper body before they drop back into their seats, generally still in the seated posture. Indeed, the restraining effect of the forward seat is less immediate than seat belts would be, but at the large vehicle's lowered deceleration impulse force, the immediacy of the restraint is far less important.

Today's motorcoaches are also built to absorb crash energies. While automotive engineers have spent years building "crush zones" into cars, motorcoaches have always enjoyed the advantage of an energy-absorbing construction. Using a "monocoque" or "unibody" design, coaches crush by small increments on impact. And rather than absorbing the entire crash impulse at the point of impact, monocoque construction allows crash forces to be distributed through the entire length of the body.

Compartmentalization also provides what might be the ideal "passive restraint" system; it delivers passenger protection without asking the passenger to take any action other than sitting in their seat. Air bags and automatic, sliding, seat belts were the automotive industry's answer to the biggest problem yet identified with seat belts: people just don't use them. As recently as January 1999, NTSB took a close look at automotive child restraint systems. It found that in 62-percent of the cases where restraints were present but serious injuries still resulted, it was because the restraint device was not used, faulty or simply used incorrectly. By its dependence on compartmentalization and energy-absorbing construction, motorcoaches have also avoided an unpleasant side effect of belts: "soft tissue" injuries which are caused by belts themselves.

Is there more we could do?
Compartmentalization, monocoque construction, energy-absorbing, high-back seats and soft covered interior elements all contribute to the passenger protection of motorcoaches, but they are intended to work together as a "passenger protection system." There are some places, though, where every element of that system may not be present. In the United States, for instance, belts are currently mandated for coach drivers, a seating position which doesn't benefit from compartmentalization. The NTSB has also been assessing the safety value of belts or other restraint devices such as exaggerated modesty panels in other "exposed" seat positions aboard coaches: the forwardmost seats, the center rear seat which faces an aisle, and seats behind desk or table installations.

Another element of the protective "system" used in motorcoaches has come under question in recent years, as well. Investigations of fatal bus and motorcoach crashes over the past 20-years have shown that a passenger death usually occurs in one of two ways. The first is a massive intrusion into the passenger space. In a collision with a large vehicle or stationary object, passengers within the intrusion zone are at obvious risk. The second most prevalent cause of death is by ejection or partial ejection. There is strong evidence that most crashes are survivable when passengers stay inside the vehicle. That's drawn attention to FMVSS (Federal Motor Vehicle Safety Standards) 217 which determines construction standards for bus and motorcoach windows.

Created in an era when gasoline engines were dominant in buses, FMVSS #217 require manufacturers to install windows which can be opened for use as an emergency escape during a fire. Since that time, of course, virtually the entire motorcoach world has moved to diesel engines, significantly reducing the likelihood of a fire. At the same time, customer demands for a more "European design" have led to massive, panoramic, window sizes. In circumstances involving violent vehicle behavior, such as a rare rollover, the windows and latches required by FMVSS #217 may fail; the result can be passenger ejection. Even when they function as designed in an overturned coach, the weight of the large windows has proven difficult to many escaping passengers. In recent months, NHTSA has acknowledged to UMA that there's a need to revisit its window design mandate. But its clear that window escape problems have accelerated discussions of seat belts.

Today's environment
We've seen that a motorcoach's size and its construction reduce G forces in a crash and contain and effectively protect the passenger. And we know that the regulators and safety experts have responded to the scientific facts by resisting the urge to apply ineffective (but the most popular) remedies, seat belts. But the politics of seat belts are far less clear.

From the time of our child's first ride home from the hospital, proper restraint is drummed into our consciousness. Buckle Up campaigns dating back 30-years have effectively convinced drivers and auto passengers that belts are "The Answer." Attorneys for injured coach passengers accusingly point to the absence of seat belts in an attempt to capture an easy verdict for their client, despite the overwhelming evidence that belts wouldn't have helped. Emotion has overtaken the logic in many cases. Despite very recent testimony from safety experts that lap belts in school buses may actually present a greater hazard to young bodies, many belt advocates continue to lobby for a school bus belt mandate.

Politics, not safety, have driven lawmaking in Europe, as well. Seat belts have been required in Europe at non-compartmentalized seating positions since 1988 and in all seating positions for the past two years. Testifying before the NTSB in the summer of 1998, though, European officials openly admitted that the installation of belts was a "political" decision, not one driven by safety research. Starting in Great Britain in response to a particularly bad crash, political winds carried the seat belt mandate across the Channel and throughout the European community. At the same time, they acknowledged vastly different driving conditions than American motorists encounter. For instance, motorcoaches are limited to highway speeds of about 65-miles per hour in Europe, even on highways with no speed limit on automobiles. The differential often leads to violent evasive maneuvers and a much higher incidence of rollover on European roads. In acknowledgement of the much different physics of the large vehicles, the European mandate requires only a 6.6-G seat belt load rating for full-sized coaches. It also requires only the use of two-point (lap) belts.

Professional motorcoach operators in America have clearly established and accepted the evidence that seat belts would do little to advance the cause of passenger safety. And since NHTSA's 20-G load rating requirement remains the only standard in effect for seat belts in America today, the task would seem virtually impossible. Trying to install a 20-G seat belt on today's motorcoach could easily add another 10,000 pounds to the vehicle by forcing new securement structures. It would reduce also cargo and seating space, cut average fuel economy significantly and severely limit the seating configurations available. Europe's accepted 6.6-G belt load standard would clearly not meet existing NHTSA rules.

The bottom line
Safety, above all else, is the primary goal of this Association and its members companies. After all, safety is good business. The numbers confirm the fact that the motorcoach is the safest highway vehicle on the road today. But at the same time, we aren't smug in our confidence that today's vehicles can't be made even more safe. Neither NHTSA nor any other highway safety agency, public or private, has conducted definitive crash testing on today's motorcoaches. UMA stands eager to step up to the task as a cooperative partner if and when such testing is conducted. And we stand ready to promote significant safety enhancements when their value is proven.

With its manufacturer associates, its safety specialists, its legal team and all of its resourcefulness and experience, UMA is also trying to help sort out the issues for you. We know that there are no easy answers, especially when you're faced by riders, parents, reporters and the inevitable phalanx of challenges to the "seat belts wouldn't help" response which is most honest of them all.

The fact remains, however, that seat belts are not just "not mandated," today they're clearly "not the answer." Any reporter who believes that the issue has just been overlooked by Congress, NTSB, USDOT, NHTSA, OSHA or a long list of government and safety agencies just hasn't examined the record.

If things change, we'll let you know. But until, then, brush up on your physics and settle in for a long explanation. Or ask your questioners to call us: (800) 424-8262. We'll even pay for the call.

*** Postscript: January 2000
On September 21, 1999, the National Transportation Safety Board (NTSB) released the results of a nearly-three year long study entitled "Bus Crashworthiness Issues." The complete report (SIR-99/04) can be read in summary form online at the NTSB's website address: http://www.ntsb.gov/Publictn/1999/SIR9904.htm or in its entirety at http://www.ntsb.gov/Publictn/1999/SIR9904.pdf as an Adobe Acrobat "pdf" file. The report addresses both motorcoach and school bus issues.

In its report, the Safety Board praised the level of passenger protection afforded by the compartmentalization of today's school buses and motorcoaches, but called for continued redesign and testing of both vehicle types to better contain passengers in the vehicle seating compartment during the most violent, rollover, crashes. Though long a staunch proponent of seat belt usage in highway vehicles, the Safety Board did not recommend the installation of belts in large passenger vehicles. In short, the Board indicated that today's compartmentalization of passengers provides the maximum amount of crash protection possible until entirely new devices or designs are developed and implemented. It also asked that those new designs be the result of actual crash testing of both styles of vehicle. The National Highway Traffic Safety Administration (NHTSA) is currently conducting a crash test program on school buses, but has resisted a similar program for motorcoaches.

UMA strongly recommends that persons interested in the issue of large passenger vehicle crash protection or passenger restraint systems read the complete NTSB report.

Presented on the STN Web Site by permission of the

United Motorcoach Association
113 S. West Street,
Alexandria, VA 22314
(800-424-8262) (703-838-2929)
http://www.uma.org.