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Special seats on “crumple zone” tracks and a mechanical arm to prevent cars from passing were just some of the ideas Texas A&M University senior mechanical engineering students proposed for making school buses safer. The project was part of a year-long two-semester senior design course in collaboration with students from the College of Architecture at Texas A&M. Dr. William Schneider, professor of mechanical engineering, taught the design course with Associate Professor Tom Lalk, associate professor, and Ed Marotta, visiting associate professor.
Every year there are about 50 fatalities and 10,000 injuries associated with school bus accidents. School buses must be safer, and these students have worked hard to develop ways to make that happen. The students first identified seven areas to focus on: energy-absorbing seat tracks; a suspension system for a smoother, safer ride; ways to prevent cars from passing on the left side of the bus while it’s loading or unloading children; under-ride protection to prevent cars from sliding under the bus in rear collisions; more accessible and easier-to-use emergency exits; an internal sensor for seat belt monitoring; and external sensing to alert the driver when objects are within a certain distance of the bus.
In one project, the energy dissipating seat system, the students designed a bus seat that slides along a track. During a frontal collision, the seat slides forward, crumpling a type of honeycomb in the track. The honeycomb dissipates the energy from the crash so that the child in the seat absorbs less of the impact. The honey-comb is replaceable, so the seat system can be reused after a collision. Because about 70 percent of bus crashes are front-impact, this system will limit childrens’ injuries by limiting the force exerted on them.
One team proposed replacing current window emergency exits with a ramp that extends out of the side of the bus in a telescoping design. The students designed a system that would automatically deploy in the event of a collision, but also included a manual control that the driver could use to lower the ramp.
In another project, students proposed using a series of active infrared sensors outside the bus to create a perimeter around the bus. The sensors would alert the driver when a child or another object enters the perimeter. Additionally, a video monitor helps the driver see over the front bumper.
Two teams developed side arms to prevent cars from passing on the left side of the bus while children are boarding or getting off the bus. The first design uses a pneumatic latch at the rear left of the bus to swing an eight-foot-long arm out from the side of the bus. A second option is a retractable arm that extends out from behind the left rear tire. Both arms act like the safety arm at a railroad crossing to keep cars from driving around the bus.
Another team developed a seat-belt monitoring system to make sure kids are buckled in while on the bus. The seat belt system also prevents drivers from accidentally leaving children on the bus overnight or for extended time. Bus drivers must perform pre- and postoperative checks on the buses, but they sometimes skip the postoperative check, which can be a liability issue. This system makes sure the drivers perform the checks by using the ignition key to turn off an alarm system at the back of the inside of the bus.
The largest team was the suspension team, which designed a system for a smoother, safer ride and prevents the bus from rolling over. The suspension team consisted of four subgroups that worked on a particular aspect of a bus’s compressible liquid active suspension system: The fluids team designed a system to provide the hydraulic forces needed to control the suspension; the mounting team devised a way to mount the components to the bus; the vehicle dynamics modeling and control team modeled how the bus would perform with the suspension system; and the corner module team put it all together. A final team, the systems integration team, coordinated the projects and documented each team’s work. Most of the modifications proposed can be retrofitted to current buses. For more information, contact: Dr. William Schneider, 979/458-0116, wschneider@tamu.edu.
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