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School Bus Extrication - Part 2

School Bus Extrication - Part 2

David Pease, Carolina Fire/Rescue/EMS Journal

I hope this column finds everyone well. As I write this next part on bus extrication, and we look further into how buses are constructed, I have had the opportunity to teach several more classes on bus extrication. Each time I do a class I always learn more from my students and being able to experiment with techniques. We have also just celebrated Thanksgiving and are moving into the Christmas holidays. When you read this, Christmas will have come to pass.

I know I am getting off track a bit, but I hope that everyone had a most joyous holiday season, and a safe one too. With the holiday season we see more motor vehicle crashes, and also illnesses as well. The holidays can bring on stress for us and our families, especially with the jobs we do. Please take the time to enjoy your families and be thankful for them. It is interesting that people in general, tend to much nicer over the holidays. Wouldn’t it be nice if they were always like that. Well anyway, Happy Holidays from myself and the entire Reds Team.

School buses use a skeletal system of frame design. This makes the bus extremely strong and minimizes interior penetration when involved in a crash. The galvanized steel used in the bus, and the molded steel channels that make up the frame, increase the integrity of the bus. Whether the bus strikes something, rolls over, or is struck by another vehicle. Understanding this framework and design will help in your access and removal of victims. Very seldom will you run across victims actually pinned in a school bus. The mere construction of the bus helps to prevent that. However, you will have to gain access and be able to remove victims that are injured.

We will start at the bottom and work our way up. The floor of the bus is the strongest and most difficult to gain access. The floor consist of a steel frame of 8 to 12 gauge channel with spacing approximately 12 inches apart, running the length of the bus. The floor consists of 14 gauge sheet metal over the steel framing, and then a plywood sub-floor placed over that. A one piece steel bow framing of 14 gauge steel runs the length of the bus and between each window. This steel bow frame can extend to the bottom of each skirt for added side impact protection. This steel member generally runs from one side of the bus to the other as one continuous piece. On the newer made buses, a piece of heavy duty steel serves as an inner seat rail and makes a bumper that encircles the steel floor. The bus may have up to 4 rub rails made of molded 14 gauge galvanized steel running the length of the bus. One is usually found running under the side windows, one is around floor level and the other one or two are found in between. Also, just below the windows you may find a 1” by 1” 11 gauge steel angle welded to the bow frame. This again gives added strength and protection.

You will find two 16 gauge steel roof crash rails running from front to back on the roof. These also attach to the bow frames that encircle the bus. The rear of the bus uses corner post made form 14 gauge steel, formed from an 11 inch piece, and extends from the floor to just above the windows. The inside of the post may be reinforced with steel gussets for added strength. The rear bumper is a 3/16” steel wrap around that gives added rear protection. The bus is covered with galvanized sheet metal on the outside, and insulated on the inside. The interior is then sheeted with another layer of galvanized sheet metal. I think you can easily see that school buses are constructed in a very substantial manner, making it protective to the students inside. This also makes it a little more difficult for the rescuers on the outside.

The electrical systems are the standard 12 volts, but with multiple batteries wired in parallel. The batteries are usually found at the bottom floor level, just behind the driver’s side. When disconnecting the electrical system, you can cut and tape the negative cable first, then cut and tape the positive cable. On your standard type “C” bus the engine is located in the front, while on your “snub nose” extended bus, the engine may be located in the rear.

Federal Motor Vehicle Safety Standards for School Buses dictate certain requirements in bus manufacturing. Smaller buses utilize hydraulic brakes, where your larger passenger buses use air brake systems. Depending on the size of the school bus, you may find either type of braking system. Buses have two driver’s seat options, one being a mechanical seat and the other an air lift seat. The standard also governs such things as weld integrity for the external metal sheeting, and rollover protection.

I hope this has helped in your understanding of general school bus construction. In my next column we will look at some of the techniques for stabilizing and gaining access into a school bus. If there is anything you would like to see in my column, please shoot me an email and let me know. I am always interested in techniques that you may know that get the job done. Until next time; stay safe, train hard, and you can never have too much knowledge or experience, so strive to be your best.