The characteristics of a bus or coach exterior and interior can effect its ability to avoid a collision, and to protect passengers should one occur. Parts #2 (Structures & Suspension Systems) and #5 (Seating) of this series dealt with major elements of exterior and interior crashworthiness. This installment addresses additional elements whose features may be somewhat less familiar, including some that may go unnoticed.
This installment also includes the treatment of some features germane to other types of buses – particularly school buses and transit buses. And it includes a few that NBT readers may consider far-fetched. But these features are worthy of consideration in the greatly-enhanced role that I believe motorcoaches and over-the-road buses will and should play in our nation’s near-term and long-term transportation future.
A few exterior bus or coach elements either protrude from the body or protect components which do. Their inclusion or tweaking can help protect the driver, the passengers and the vehicle in both the short run (i.e., a collision) or long run (i.e., via deterioration):
Tow hooks. Tow hooks are often the lowest point on the bus or coach – particularly when the angles of approach or departure are not severe and/or overhangs are substantial. When tow hooks get “hung up” on a driveway or roadway irregularity, the interference can stop the vehicle in its tracks, jettisoning the passengers forward. These impact forces are also transferred to structural elements and components, leading to deformation and stress cracks, and occasionally compromising suspension system elements. One clever approach to mitigate these problems is to configure the tow hooks to lie horizontally or obliquely, increasing clearance by several inches.
Skid Plates. Skid plates protect the front stepwell, vulnerable to jarring from sharp right turns alongside high curbing or other objects. Skid plates also help preserve the geometric integrity of the stepwell, as well as framemembers surrounding it. Stepwells deformed “out-of-square” may lead to door, ramp and front lift platform problems. Helping to absorb the curb-side, front-corner impacts also extends the life of sensitive electronic, pneumatic and mechanical doorway components. Because skid plates can be cracked and/or scraped, they are good candidates for stainless steel composition.
Shock-Absorbing Bumpers. Shock-absorbing bumpers involve considerable front-end costs. However, they may pay off in a single front- or rear-end crash scenario by lessening the crash forces exerted on the passengers. They eliminate “fender-bender” damage by definition. Insofar as durability and crashworthiness, these appendages lessen the deformation and fracturing of structural elements that may occur in even moderate-impact collisions, as well as provide cushioning to sensitive electronic and digital components.
Fuel Tanks. With the exception of school buses (as per FMVSS #301), bus and coach fuel tanks are not subject to any crashworthiness standards. In fact, neither buses nor coaches of any type must be subjected to any front-impact crash tests. Compliance with FMVSS #301, which ensures only fuel system integrity, is a design and engineering afterthought for motorcoaches and integral buses. Otherwise, fuel tanks are less vulnerable to crash impacts if positioned inside the framemembers – as most are. But this positioning is not characteristic of all conversions. Baffling is also worth considering: When an already high-center-of-gravity motorcoach full of luggage and passengers is traveling around a less-than-perfectly-banked freeway curve, at full speed, on a rainy evening, the last thing it needs is a wave of fuel sloshing against the tank’s sidewall to further increase rollover propensity.
Structural and Suspension System Asterisks
Apart from the form and configuration of vehicle structure (see “Buying Tomorrow’s Buses Today, Part 2: Structures and Suspension Systems” in NBT, Part 2, April, 2006), a number of refinements may also help improve crashworthiness:
- Dual-strata Flooring. Most integral bus and coach floors are constructed of a combination of plywood sheets and a steel plate. The same is not true of many conversions, as their standards are sometimes defined by state-by-state school bus specifications – which do not always require steel plates. Floors constructed only of plywood can crush, buckle and splinter upon severe impact. In worst-case scenarios, seating and wheelchair securement anchorages may be compromised. Where the flooring of a “standard” conversion may not contain steel plating, it is sometimes available as an option – if only to accommodate markets in those states where it is required for school bus variations.
- Anchorages and Structural Framemembers. Seat legs and wheelchair securement hardware are often attached through the floor via nuts tightened against oversized washers. This drill-and-twist approach is lest costly and time-consuming than securing anchorages to a vehicle framemembers, and they can be attached to virtually any points on the floor plane. In contrast, securing these anchorages to structural framemembers makes the attachment points less accessible (for repair or retrofit purposes), and encompasses some design constraints since the framemembers criss-cross the floor only along selected intervals. However, affixing anchorages to structural framemembers generally translates into a stronger and more reliable attachment.
- Axle Weight Distribution. Many vehicles’ GVWRs simply match the combined GAWRs of their respective axles. But such requirements reflect perfect distribution of the loads. When a fully passenger- and luggage-laden motorcoach or over-the-road bus is rounding the final curve of its trip to Slot Machine Heaven, the rush of over-anxious gambling addicts toward the front entrance door may overload the front axle – an axle that, in some cases, can be overloaded by several thousand pounds simply when there are fewer passengers riding behind the rear axle, and the vehicle is not even filled to capacity. While overloading tandem rear axles is almost impossible, front axles can easily be overloaded. To mitigate this risk, front axle GVWRs should accommodate a less-than-perfect distribution of loads, and the combined GAWRs should exceed the vehicle’s overall GVWR.
- Rollover Protection. Only school buses are required to undergo roof-crush or “roll-over” certification (FMVSS #220), whereby the vehicle’s roof must withstand 1.5 times the vehicle’s GVWR with a minimum of deflection (roughly 5 ¼ inches) and the windows not pop out. Most motorcoaches and integral buses meet the deflection standard as an afterthought – even though large motorcoach windows present an engineering challenge insofar as window retention. Because buses and coaches charging fares are considered “common carriers,” and their operators held to the highest standard or duty of care, it may not bode well for their owners if, following a rollover, evidence suggests that the vehicle did not meet the standards of a school bus costing a fraction as much, and which may not even be classified as a common carrier in many states.
- Kneeling Features. Kneeling features are an engineering afterthought on vehicles equipped with pneumatic suspension systems. And they are becoming increasingly common on motorcoaches. They can make a big difference to many of the 60% of motorcoach passengers who are elderly, as well as to disabled passengers and small children. On buses containing a rear door, it makes sense to configure the kneeling feature to lower the entire curb-side of the bus, not just the right-front corner.
Dual air horns are a sorely-overlooked and heavily-underutilized tool for accident avoidance. They must be easily-, quickly- and intuitively-accessible. Particularly in the era of headphones and cell-phones, they must also be loud. Consideration should also be given to also mounting them in the rear as well as the front. In many bus modes, more passengers are injured just before boarding or just after alighting than in incidents occurring while they are on board. When your driver alights a passenger, watches him walk alongside to the rear and step behind the coach, and observes an oncoming motorist racing toward it, the driver needs to blast out the passenger’s eardrums. If the reader thinks that liability ends the minute a passenger leaves the stepwell, he or she has not been paying attention to past installments of “Safety and Liability.” Strobe lights flashing simultaneously with blaring horns may be even more helpful – particularly as some passengers or pedestrians are hearing- or visually-impaired.
Anti-lock braking systems are standard equipment on buses and coaches. Yet other brake system components and features are also worth considering:
- Brake System Size: Brake systems are “sized” for original equipment. When a converter adds mass to an OEM vehicle, the brake system can be “undersized.” This shortcoming can be particularly problematic on stretch limousines, which fly below the regulatory radar: In the most extreme cases, a stretch limo’s unladen weight can be substantially greater that of its OEM version – not even considering the increased weight from larger passenger loads, luggage, and deluxe features like TV monitors and refrigerators. Because decreases in braking capability are geometric rather than linear, these distortions in design are exaggerated at the performance level. A sound rule even for the specification of OEM vehicles is to select the largest brake shoe size offered. Conversions that significantly exceed the OEM van’s or chassis’ GVWR would do well to contain the largest brake system available.
- Retarders. Particularly where vehicles will be traveling on long downhill slopes, electromagnetic or transmission retarders are a wise inclusion: Retarders do not add significant braking capacity. However, engaging them periodically relieves heat buildup on selective brake element surfaces, permitting the brakes to work more effectively when they are applied. Retarders are particularly important for buses and coaches deployed in mountain driving.
- Jake-Brakes. When Jacobs Brakes are engaged, they force a column of exhaust toward the engine, creating back-pressure that slows the engine down and decelerates the vehicle. However, most Jake Brakes are extremely noisy: Buses and coaches containing them are not permitted, as a regulatory matter, in certain jurisdictions (for example, New York City). While such regulations are rarely enforced, buyers must beware of quirks in the operating environment – particularly in venues where law enforcement is hostile to motorcoach services.
- Parking Brake Mounting Position. If at all possible, mount the parking brake on the wall-side of the driver’s compartment – where passengers cannot disengage it accidentally.
Fire Prevention and Suppression
The importance of fire suppression systems has been highlighted recently by a spate of catastrophic accidents. However, fires erupt in places other than the engine compartment. So consideration might also be given to installing fire-retardant seat covering materials and seat foam – the former a requirement in school bus seats costing a fraction as much as most motorcoach seats.
Buses and coaches meet industry standards without some accoutrements that are standard features on other vehicles and buildings. Among these features, consideration might be given to the “anti-explo” fuel tank technology commonly employed in racing cars. This technology also inhibits fuel sloshing, while consuming only a negligible percentage of fuel tank capacity.
Finally, sprinkler systems are practically unheard of in public transportation vehicles other than ships, trains and selective aircraft. Yet they are formal requirements of public buildings, houses and even rental units. As the spectre of liability continues to exaggerate the impacts of less-than-perfect safety, we should not ignore sprinkler systems in our long-range development plans. This is particularly true as buses and coaches increasingly perform expanded roles in our society as relief and rescue vehicles (see “Plans, Preparation and the S-word” in November, 2005 NBT).
Most aspects of illumination will be covered in the next installment of this series in NBT: Part 7: Visibility, Comfort and Security. However, Three exceptions relate to vehicle exterior and wiring:
- Reflective Striping. One of the five core elements of the Smith System (a classic primer on defensive driving) states, “Make sure they [other drivers] see you.” To many non-professional drivers, the collection of clearance lights, taillights, running lights, turn signals and hazard lights found on most buses and coaches during nighttime operations just as easily suggest a space ship. The same is not true of vehicles whose shapes are defined by reflective striping that outlines their side profile, front cap and rear cap. Because coaches and buses commonly operate at night, often on sparsely-illuminated roadways, making them visible as the large vehicles they are is worthy of consideration. As an afterthought, front caps are the least often striped. Yet motorists traveling in front of buses or coaches need to know that the 20-ton monolith following them cannot stop nearly as sharply as can their two-ton automobiles.
- Light Failure Monitors. Because some of their lights operate as traffic signals, school buses commonly contain light failure monitors – requirements in some states. These devices inform drivers about lighting failures the moment they occur. Particularly when long distances lie between successive pre- and post-trip inspections, the burning out of a bulb can precede hundreds of miles and several hours of driving. Because many lighting dysfunctions can be trouble-shot by drivers, and stranded drivers can at least adjust their driving when they cannot be, the driver’s immediate notification of a lighting failure can prove valuable.
- Roof Hatches. Roof hatches are almost always centered over the passenger aisle. This positioning may accommodate some passengers when, after a rollover, explosion or serious collision, the bus or coach lands on its side. But it is virtually useless when the vehicle lands on its tires. Were the roof hatches “staggered” – one on the curb side and one on the street side – they would still provide egress when the bus lands on its side. But they would also provide reasonable egress (for at least some if not most passengers) when the bus lands upright, since the passengers could reach them by standing on the seats directly below. And color-coding the seats below the respective hatches would help make the escape routes more intuitive.
Crossing Control Guards
Stop arms, red and amber overhead flashers, and (in at least 30 states) crossing control guards are formal school bus requirements. In truth, crossing accidents are far more common to school buses (which contain these devices) and transit buses (which do not) than motorcoaches. However, there are exceptions. Particularly in urban sightseeing and commuter-express duty cycles, motorcoach passengers and pedestrians are subject to the same or similar crossing risks as their school bus and transit counterparts. While flashers and stop arms would be inappropriate for such vehicles, the same is not true for crossing control guards: In almost half the 38 crossing-related incidents I have examined forensically, the crossing orientation of the passenger was the opposite of that needed for the type of vehicle involved (i.e., transit passengers crossed in front, while school bus passengers crossed to the rear). When passengers cross in front of a school bus, the driver at least expects them. The opposite is true when they step in front of another type of bus or a motorcoach. A crossing control guard would present a serious deterrent to many or most of these would-be crossers.
For those readers who believe they are immune to liability in incidents where third-party vehicles run over their passengers, now would be a good time to turn off Ozzy and Harriet and start reading “Safety and Liability” in NBT back-issues. The inclusion of a crossing control guard on buses and coaches deployed in multiple-stop duty cycles is an idea worthy of serious consideration. (The inclusion of school bus mirror systems will be treated in the next installment of this series in NBT: Part 7: Visibility, Comfort and Security.) Should one of your passengers be struck while crossing, you want to be able to demonstrate that you went beyond the industry standard – not forced to argue that you merely met it.
Motion Detection and Warning Systems
Motion detectors have been used on buses for at least two decades, beginning with the Delco “Forewarn” and VORAD systems, among others. More recent entrants into the market have included Romeo Rim (which embeds the devices into its high-tech bumper systems), Ackton and Drive-CAM. Most recently, the beeps and flashes have been integrated with video cameras. High-capacity hard-drives now provide thick memories with large spans of time between the frequency of change-outs and over-writes.
While drivers are taught to “rock and roll” (i.e., move their heads around) to compensate for otherwise blind spots in visibility through rear-view mirrors, some areas around the vehicle are still more difficult to see than others. Without a camera or periscope (see www.rearscope.com), seeing behind the vehicle is obviously impossible. Backup alarms and sensing devices can address this problem. However, most are configured to trigger only when reverse gear is engaged. Far more common than backing into passengers is the scenario whereby passengers who just alighted step out from behind the bus into the path of an oncoming vehicle. Bus and coach drivers may be able to mitigate these crises if they are alerted to the presence of passengers behind the bus. If you elect a back-up sensor or alarm, think about having it configured to engage in every gear: Regardless, if concern for the passengers does not evoke sufficient motivation for this approach, note also that your drivers may find it helpful to know when they are about to be rear-ended.
Radios and Music Players
Like video monitors, AM/FM radios and CD players are noteworthy and well-justified passenger accommodations. But like video monitors, bus and coach drivers should not have access to speakers other than those through which they can communicate with a dispatcher. Turning up the radio to ward off fatigue is an old wives tale. Instead, drivers must be able to hear, not simply see (see “Sights and Sounds” in NBT, September, 2005).
In a marginally-managed bus or coach system, isolating drivers from music can boomerang: They may be tempted to listen to their own music through headphones. But addressing this problem by “giving them safer nukes” is not a prudent solution. Passenger management is an important operating function, particularly on motorcoaches containing restrooms to and from which passengers may walk while the vehicle is in motion. And passenger management is a heightened concern for the 30 percent of motorcoach passengers who consist of schoolchildren on field trips. Drivers should not have to recall the totality of their training in the nanosecond during which an incident begins to unfold. They must continuously and proactively see and hear during every moment the vehicle is moving, as well as those short spans of time immediately before and afterwards. Do not dilute the drivers’ ability to perform these functions by providing them with entertainment during the ride.
Clutter and Such
A few odds and ends do not fall neatly into categories:
- Flashers and Strobes. The degree to which certain types of lights can flash is largely a state regulatory matter. So be careful when selecting features and configuring the overall envelope of safety that you intend the vehicle to provide. Otherwise, apart from possibly blinding oncoming motorists, the more attention you can draw to your vehicles, moving or still, the better. This is particularly true if the vehicles occasionally operate in a fog or snow environment.
- Hood Ornaments and Protrusions. Protrusions are not found simply on old Pontiacs. While we have largely removed them from vehicle exteriors, we have not mirrored this performance on the interior. Keep passenger-counting devices and other objects off the dashboard. Keep oversized fareboxes and jump seats out of the stepwell. Consider softening the materials used for fold-down trays. The paramount exceptions to this principle are handrails, stanchions and grab handles.
- Wheel Chocks. Unless you plan to restrict your fleet’s duty cycle to the desert, consider spending $20 on a wheel chock. Do not provide the victims’ attorneys with evidence they can hold up and wave around during their closing arguments (see “Cheap and Portable Evidence” in May, 2004 NBT).
Build-a-Bear is a recent, suburban shopping mall phenomenon. Otherwise, children have been dressing up dolls for millennia. Salad bars were more recent. Configuring your computer on-line more recent still.
Specifying vehicles features falls somewhere in between these trends, chronologically. But at no time has performing this function thoroughly been as critical as it is now. When you build-a-bus today, make sure you build it for tomorrow’s operating environment … and tomorrow’s litigation environment.