Inspired by the safety equipment in roller-coaster cars, two mechanical engineering students have invented a restraining bar system to protect children in school buses during head-on collisions or rollover accidents.

Using a $30,000 crash dummy and two seats borrowed from an actual school bus, 22-year-old seniors Stephen Pantano, of Cranston, R.I., and William Thompson, of Newtown, Pa., recently tested the device in a university lab by simulating a 15-mph head-on crash. The bus seats, anchored to a wooden platform, were hoisted about seven feet up, facing the lab's concrete floor. The platform was then dropped, with the crash dummy, borrowed from the Applied Physics Laboratory, seated behind the students' heavily padded lap bar. The dummy was wired to an accelerometer that measured the impact to the head during the crash.

After a simulated crash, Stephen Pantano, a senior majoring in mechanical engineering, makes sure a dummy stayed securely behind a lap bar he helped develop.

Although further analysis and tests are needed, the undergraduates and their faculty advisers were pleased by the results of the simulated crash. "The bar didn't collapse, and it kept the dummy in the seat--exactly where you want it," said Pantano. "We covered the bar with three layers of foam padding, which helped spread out the force of the crash."

Resembling the systems found in some amusement park rides, the students' restraining bar would be bolted to the floor of a school bus. After the children were seated, the bar would pivot down to a locking position in their laps. The bar features a simple manual-release lever, so children would have no trouble leaving their seats at a bus stop or during an emergency. Its inventors say the device could easily be installed in existing school buses.

The school bus safety system was one of 12 projects completed this year by undergraduate teams in the Engineering Design Project course taught by Andrew E. Conn, a Johns Hopkins graduate with more than 25 years of experience in public and private research and development. Each team of two or three students, working within a budget of up to $8,000, had to design a device, purchase or fabricate the parts and assemble the final product. Corporations, government agencies and nonprofit groups provided the assignments and funding.

In the past, Conn's students have developed a "safer" handgun that does not fire in the hands of an unauthorized user, an infra-red mouth-held device that allows a paraplegic to operate a computer from a bed, an automatic wheelchair brake and a wheelchair lift powered by a van's exhaust.

Transportation safety regulators and educators are expected to review the school bus restaining bar and the test results as part of an ongoing debate on how best to protect more than 23 million children who ride school buses twice a day throughout the United States. Each year, these trips involve about 440,000 public school buses traveling roughly 4.3 billion miles, according to the National Highway Traffic Safety Administration, which is in the midst of a school bus safety study.

Some parents and safety experts believe seat belts should be installed, but only two states require them in the most common large school buses, those weighing more than 10,000 pounds. Proponents say seat belts would reduce school bus injuries, curb behavior problems and help students get in the habit of buckling up in all vehicles. Critics, however, argue that seat belts could cause additional head and abdominal injuries and hinder evacuation of students after a crash.

Would a different type of restraint system settle the debate? Last fall, the engineering students were assigned to find out. They designed and built the restraining bar in a class project sponsored by the Center for Injury Research and Policy, based at the School of Public Health.

Andrew F. Lincoln, an injury epidemiologist at the center, pointed out that the current strategy of protecting school bus riders through "compartmentalization"--surrounding children with padded seats--as its limits. "Those 'compartments' aren't very helpful if the students don't stay within the padded area," he explained. "On bumpy roads and during rollover crashes, the kids can be thrown out of this padded area and into hard-shell areas like the roof or a window."

Thompson, one of the student engineers who designed the restraining bar, said he and his partner saw evidence of this during their research. "We looked at a security camera tape of a bus just going over a wooden bridge," he said. "The kids bounced up and hit the ceiling of the bus. That shows just how easily kids can be hurt. There's currently nothing in most school buses to protect against side impact or rollover crashes, where severe injuries can take place."

Public health scientist Lincoln stated that school buses, overall, are a very safe mode of transportation. Even so, he added, about 11 deaths and more than 8,500 injuries occur annually aboard school buses in the United States. "There is an obligation to keep children safe," he said, "considering how many buses there are and how many miles these children are traveling."

Lincoln is pleased with the padded lap bar developed by Pantano and Thompson, and he plans to bring it to the attention of school bus safety regulators. "I can see a big potential for some states to adopt this," he says. "I think the students have done a great job of creating a protective device without making it overly restraining. Of course, we'll have to make sure that the severity of trauma to the torso resulting from the lap bar is less than what might be expected without it."