School Bus Emergencies

School Bus Emergencies

RESCUE

Photo by Ron E. Moore

There are more than 41-million children enrolled in elementary and secondary public schools across the United States; and a large number of these students ride school buses.

According to the National Highway Traffic Safety Administration (NHTSA), there are more than 2,800 vehicle accidents involving school buses annually. With classes getting underway again next month, it is important that emergency personnel be familiar with the information needed to operate at a school bus rescue incident safely and effectively. By studying the design, construction, and regulations governing school buses, emergency personnel can understand more about vehicles in their response districts.

A school bus is defined as a passenger motor vehicle designed to carry more than 10 passengers in addition to the driver, and which the Secretary of

Transportation determines is to be used for the purpose of transporting preschool, primary, and secondary school students to or from such schools or school-related events.

School bus regulations, which should be familiar to rescue personnel, are promulgated nationally. The Federal Motor Vehicle Safety Standards outline the minimum vehicle design and construction features required, and spell out the performance criteria for windows and emergency exits; rollover protection; vehicle body joint strength; fuel system integrity; seat safety requirements; and the fire retardancy of interior materials. The Highway Safety Program Standard 17 on Pupil Transportation Safety, issued by the NHTSA, aids state governments in regulating other aspects of school bus safety such as color, lighting, markings, loading/ unloading procedures, etc.

TYPES OF VEHICLES

The National Transportation Safety Board estimates that there are 300,000 to 400,000 school buses in use in the United States. According to the U.S. Standards for School Buses and Operations, there are four types of school buses;

Type A: Van conversion unit

Gross weight rating is less than 10,000 pounds Entrance door is behind the front wheels

Motor is beneath or behind the front windshield Type B: Minibus type vehicle

Gross weight rating is over 10,000 pounds Entrance door is behind the front wheels

Motor is beneath or behind the front windshield Only 10% of the school bus vehicles in the United States are of the Type A or B. The remaining 90% are the larger capacity, larger size vehicles.

Type C: Conventional type vehicle Gross weight rating is greater than 10,000 pounds Entrance door is behind the front wheels

Motor is in front of the windshield

Type D; Body installed on chassis

Gross weight rating is more than 10,000 pounds Entrance door is forward of the front wheels Motor is in the front, midship, or rear of vehicle

CONSTRUCTION

Methods

There are two basic construction methods used by major school bus manufacturers;

• Integral construction; Custom built from scratch. This is very similar to the custom fire apparatus manufacturing process. The manufacturer assembles the vehicle starting with the frame and chassis assembly, proceeding item by item to the finished vehicle.
• Body on chassis method: The school bus body manufacturer installs the body unit onto a commercially available chassis constructed by a second manufacturer.

NOTE: Each construction method has feature similarities. Each method also offers its own unique construction features. Rescue personnel must be cognizant of both basic methods of vehicle manufacture.

Skeletal system

All school bus body units are comprised of roof, sidewalls, floor, front, and rear areas. Each area of the body has a skeletal system beneath the finish and trim elements. This skeletal system forms the basic structure of the entire school bus vehicle. It predicts how the vehicle will act during an accident, and affords the basis of the protective envelope designed for occupant safety and survival.

• Sidewalls are comprised of vertical load-bearing frame members. These vertical members are identified as partitions between window units. Running horizontally along the base of each sidewall is a framing element referred to as a collision beam or crash shield. This thick gauge steel member is strategically located to limit penetration of an object into the passenger compartment of the bus.

Twenty-gauge finish panels are mounted on the exterior and the interior of the sidewalls’ frame members. To meet requirements for interior noise level and warmth, insulation materials are sandwiched into the units.

An additional impact resistance item is added on the exterior sidewall. Sixteen-gauge steel “W” shaped rub rails (4%-inch wide) are placed the full length of the sidewalls. They are intended to minimize penetration during collision. Additionally, they may be used for occupant location from the exterior. One rub rail will indicate the seat cushion level; if a second rail is present, it will identify the floor level.

Rescue personnel should note that forcible entry and access openings are not feasible at levels below the bottom of the windows due to the structural and impact resistant frame members.

• The rear skeletal system is similar to the sidewall, with additional reinforcement installed to provide protection from rear end collisions.
• The skeletal framework of the parabolic shaped school bus roof consists of 11-gauge steel frame members called roof bows. These members are positioned in the roof structure running from side to side. Within this frame are 16-gauge members (known as strainers) running from front to rear, strengthening and shaping the bows. There may be as many as three of these longitudinal members in the roof skeleton.

Insulation material and wiring for lighting equipment are located within the roof’s framework. The outside and inside of the framing members are covered with 24-gauge sheet-metal panels.

Rescue personnel assigned to breach the roof structure should realize that the location of the roof bows and strainers will be indicated by the presence of the rivets used to secure the panels.

Emergency escape hatches may also be located in the roof structure. Made of fiberglass or other lightweight materials, these hatches normally open by the activation of a release mechanism from inside or simple forcible entry techniques from the outside. The hatches open 180° to provide a clear opening of at least 18 X 18 inches. There may be larger hatches provided on some buses, particularly if used to carry physically disabled occupants.

• The floor of the school bus consists of several important components. The heavy-duty vinyl or rubber floor covering is applied over plywood sheets and 14-gauge metal panels in most of the full-size buses. The smaller conversion type vehicles will have ½or ⅝-inch plywood sheets placed on top of the existing vehicle floor. Structural members, acting as floor joists, are spaced as close as every nine inches along the underside of the floor. Rescue personnel should note that forcible entry and access attempts to breach the floor should not be considered as a routine entry point, due to the excessive time that would be involved.
• The undercarriage of the bus is a substantially reinforced area. Eightgauge angle bar, 12-gauge channel stock, and 14-gauge sheet metal are the materials that form this area. There are also additional guard loops around the entire length of the drive shaft to prevent injury to the passengers should the drive shaft fall to the ground. Forcible entry through this area (as mentioned before) is indeed difficult and time consuming. Another entry site should be selected if possible.
• The rough openings for the side and rear windows are framed by the vertical frame members, the roof edge, and the top of the sidewall. The partitions between windows are hollow members of several layers of sheet metal. These areas can be forcibly removed by rescue personnel with sawing, chiseling, or cutting actions.

The windows are laminated safety glass framed in extruded aluminum.

The windows are mostly of the splitsash design and are affixed into the rough openings with rivets or similar devices. Typical bus windows open from the top, providing an opening of approximately 9 X 22 inches or half the window.

To provide a larger opening, some of the windows are designed as emergency exits and are so labeled inside the vehicle. From the exterior, the exits are readily identified by the appearance of hinges located along the top side of the window frames. Once opened, they provide a two-foot square opening into the side of the vehicle.

These windows and sash units do not have hold open devices to secure the window and frame in the open or up position. Therefore, rescue personnel operating at the scene of a bus incident must provide their own means of securing these windows in the open position or anticipate the removal of the entire split sash unit.

• On the smaller conversion-type school bus vehicles, the stock version one-piece laminated safety glass windshields are set into the vehicle body by means of the multi-piece rubber mounting gasket.

Windshields on full-size buses consist of two flat sheets of laminated safety glass. These sheets are also secured into the vehicle body with a rubber gasket mounting.

Rescue personnel should note that removal of the windshield glass is readily accomplished from inside or outside the bus. The windshield glass and the rubber gasket could be pushed or pried out, making for large access and/or egress openings in the vehicle.

Rear window glass is also laminated safety glass, and comes in flat sheets. The rear windows are mounted in removable rubber gaskets.

continued from page 26

Courtesy of the Wayne Corporation

Seats

The two types of seats in buses are:

• Driver seat is an adjustable bucket type. There is also a floor mounted seat belt and/or shoulder harness assembly for the driver’s use.
• Passenger seats, for the transportation of students, are usually framed with one-inch tubular steel. The seat is secured into the bus floor and into the sidewall area. Detachable foam rubber seat cushions and seat backs are covered with a vinyl upholstery material. After 1975, seat backs were changed from the low style to the high-back style, 28 inches high. Working room for rescue personnel inside these buses is limited.

Lap style seatbelts for passengers are an option of the vehicle’s owner or mandated by regional ordinance. In buses used to transport physically or mentally handicapped persons, positive body restraint harnesses may be found in specially designated seats.

Aisle

The position of the seats inside the school bus establishes the width of the vehicle’s interior aisle. The aisle of suburban type bus vehicles could be as narrow as 10 inches. Aisle space in van conversion buses increases to approximately 12 inches. Full-size school buses may have aisle widths between 12 and 15 inches. Rescue personnel should note that the width of a typical emergency medical longboard device is 18 inches.

Wheelchair-equipped vehicles generally have 30-inch wide aisles, permitting movement of wheelchairs inside the vehicle.

Interior

Headroom inside school buses, measured at center aisle, can vary from a minimum of 60 inches on the small van conversion buses to 77 inches on the full-size vehicles.

• Ceiling and sidewall interior finish panels are of typical 24-gauge sheet metal. These panels, secured to the internal framework of the vehicle, introduce a potential for occupant injury during a vehicle accident. The edges of the interior ceiling and sidewall panels may separate, exposing the occupants inside the vehicle to potentially severe lacerations. This phenomenon is referred to by rescue personnel as the “cookie-cutter” injury. The introduction of interior panels running the full length of the bus have been developed by some school bus manufacturers as a means of reducing the occurrence of this injury problem.

Doors

There are various types of entrance and exit doors on school buses, each serving a function. The doors are strategically located to maximize exit paths after a motor vehicle emergency.

• Entrance doors on small, suburban type buses remain as stock versions provided by the original manufacturer. The latch and lock mechanism is the Nader safety lock found on most motor vehicles since 1973.

Conversion type (slightly larger than suburban) buses are modified during the conversion process. Although the driver’s door is untouched, the passenger side front door is drastically altered to suit the needs of the school bus owner/operator. Also, the window glass is permanently fixed in a closed position, and the door handles, armrests, and window cranks are removed, as are the latch and lock mechanism in the door body. The sole means of opening or closing the front passenger exit door is an installed over center pivot control arm at the driver’s side.

The passenger side front door on the full-size school buses are of several different opening types. Basically, it will be a two-part, split-type door opening in or out, or any combination thereof.

The front door also may be a center, hinged-type door that opens by folding forward or rearward. Regardless of the type of door, the sole means of opening the door or securing it in the closed position, is once again the manual over center pivot control arm mechanism. When open, the front school bus door affords a typical horizontal opening clearance of between 22 and 24 inches, and a minimum vertical open clearance of approximately 68 to 72 inches.

Some school bus owners specifically request an alternate means of controlling the front door, such as an air-actuated control mechanism. The main switch is usually located to the left of the driver’s instrument console. If so, there will also be a back-up emergency release mechanism in the stairwell at the exit door inside the vehicle. The readily identifiable release button or switch permits the air lock device to release its grip on the door. At that point, rescue personnel can manually move the door through its normal path of travel, successfully opening it.

The air override release mechanism may not be required if there are two operable doors located along the same side of the bus.

• The rear exit door is designed to give occupants inside the vehicle a means of exiting if the front door doesn’t function or is blocked.

On van conversion type school buses, we may find either one or two rear exit doors. On the small suburban and the full-size school buses, there is usually one large rear exit door. There is no locking device on these rear doors, and all open outward by manipulation of a lever to release a latch mechanism. These doors may be opened from the exterior as well as the interior.

The rear exit door is held secure by three latch points. The main latch is at the edge of the door near the control handle, and the other two are found at the top and bottom of the door, holding fast into the bus body and the floor assembly. Rescue personnel should note that forcible entry through a damaged rear exit door is effected by either removing the laminated safety glass or by freeing all three contact points of the door latch simultaneously.

Photo by Ron E Moore

NOTE: Rear engine buses do not have a rear exit door. Access from the rear is only through the removal of the laminated glass.

• Additional exit doors on buses with a capacity of 31 persons or more requires an additional exit door along the driver’s side of the vehicle. This door, known as the “third door” or the “left-hand door,” provides an opening of 24 X 48 inches and is secured with the same three-point latch mechanism as on the rear door. Access is more easily attainable from the exterior, as the interior access to the latch mechanism may be severely restricted by the installation of the student seats.

HAZARDS

School bus fuel systems may include gasoline or diesel oils as well as propane, liquified natural gas, or compressed natural gas systems. Gasoline tanks are usually located on the passenger side in close proximity to the regular fuel tank.

Data and statistics

The National Highway Traffic Safety Administration’s fatal accident reporting system for the period 1975 through 1978 shows that annually there were:

Fatal school bus accidents 15

Fatalities (students) 147

Fatalities (drivers) 27

Non-fatal accidents 2,800

Injuries (students) 3,900

Also reported is the fact that 90% of the injuries in an average year are considered minor to moderate. Seventy-eight percent of the fatal accidents result in three passenger deaths, and in 58% of the accidents, only one passenger fatality resulted.

Batteries

Batteries on smaller suburban buses remain in the standard position provided for by the chassis manufacturer. On the full-size buses, a bank of batteries is located in an exterior compartment on the driver’s side of the bus. If this compartment is empty, the batteries will be found in the engine compartment on both sides of the motor.

Once inside the school bus, rescue personnel should attempt to turn the key or push the button operated ignition system to the “off” position. This will minimize the chance of an electrical system malfunction and shut off the vehicle’s engine. Rescue personnel dealing with a vehicle equipped with the alternate fuel system should also locate and shut off the fuel system valve.

Rescue personnel outside the school bus also should be able to locate the vehicle’s battery banks and determine their status. To open the battery compartment door, rescue personnel may be able to operate the wire control rods, permitting the drawer to be pulled open. Another style of battery compartment latching device involves using a hex key or Allen wrench to unlatch the compartment door. This key is generally located inside the school bus near the driver’s area. Forcible entry methods can successfully open the key type battery compartment doors in lieu of the key device.

EXCEPTION

Although most of the full-size school buses have a seating capacity of 60 or 66, recent trends in school bus technology have resulted in even larger capacity school buses.

Within the last several years, two U.S. school bus manufacturers are offering the “super” school bus, an 8 X 40-foot long vehicle. The engine of these vehicles is located inside, at the front of the bus. This positioning is similar to the engine location in a typical van vehicle. The forward interior of the bus has been brought forward to the front bumper. By lengthening the body of the vehicle, the super bus now has a legal seating capacity of 84 persons plus the bus driver. A legally permissible “standing room only” overflow of 20% of the seating capacity is also permitted, in this case, an additional 16 persons. Hatches are also provided in the vehicle’s roof, one forward of the center, and a second near the rear of the vehicle.

Worthy of note for rescue personnel that must deal with the 101-capacity school bus vehicle in post-accident incidents, is the features at the bus driver’s operating position. Due to the location of the engine inside the extreme front of the vehicle, this area becomes somewhat congested. Once in the driver seat, the driver must tilt the steering column into his lap. This operation “traps” the driver automatically if a collision prevents him from removing the column.

In an upcoming edition of FIRE ENGINEERING, the author will present information relative to vehicles designated for physically and mentally handicapped persons. Also included will be specific information regarding proper rescue incident strategy and tactics for emergency service personnel.