Buses Roll On


Bus companies, whether for school or commercial, have always kept safety and performance at the forefront. When you consider how many lives are in their hands, it’s a must. We talked with a few leaders in the field to find out improvements that have been made over the years and where buses are going in the future.

Cross section of self-piercing rivet joint of a SAF-T-LINER C2. Image: Thomas Built Bus

Herbert Mehnert, vice president of engineering for Thomas Built Buses, High Point, NC, says the last decade has been a strong step forward. “We have seen several changes in the joining methods that we traditionally had used in the assembly line, such as the integration of structural adhesives, the implementation of fasteners that do not require drilling, and the use of robots to apply spot welds in the construction of buses,” he says. “These new techniques require careful selection of items, such as material coatings that need to be compatible with the adhesives, the gauges, and materials that can be used successfully with self-piercing rivets and the tolerance required with robotic application of spot welds.”

Both companies are exploring alternative fuel options in some of their vehicles. Image (top): Thomas Built Buses, image (bottom) Blue Bird Corporation


Safety Features

Of course, safety is the most important aspect of buses. Much of it is decided by the government, from the additions over the years of standard no. 220 school bus rollover protection to no. 221 for joint strength. But there have been opportunities over the years for companies to step up. According to Mehnert, Thomas Built Buses was the first company that made ABS brakes standard and they also have implemented brake to shift interlocks.

Bruce Miles, an engineer for Blue Bird, says the departmentalization method of seating, which he describes as “an egg crate” concept, is what’s favored, the tall padded seats and spacing absorbing energy from a child and protecting at the same time. He says the dimensions of most school buses on the inside to incorporate this are roughly 96 inches for the overall width—seats on either side around 39 inches wide, the aisle 12-15 inches in between.

With budgeting a growing concern and the uncertainty of future gas prices, fuel economy has also become a major factor. “We have sold about 1,500 CNG buses, and our customers will soon be able to enjoy another alternative fuel option, propane, in our type C and A vehicles,” says Mehnert. Their diesel vehicles have also added the urea exhaust after treatment systems. Blue Bird, which already offers buses for propane on Type A and C, has also seen its 6.7 L diesel average 9.24 mpg.

Road to the Future

Though results are encouraging, clearly the hope is to take buses well into the double digits in mpg in the future. Mehnert says they can also continue to improve on vehicle performance through composite materials for safety and improved cost. Another area is looking at how buses can further be used for the common good. Blue Bird models have been repurposed after its life in a school district for many goals—from mobile medicine clinics in Guatemala, along with mobile classrooms and libraries. But as Mehnert and Miles both remind, getting occupants safely from point A to point B will remain the top focus.

Eric Butterman is an independent writer.

We have sold about 1,500 CNG buses, and our customers will soon be able to enjoy another alternative fuel option, propane, in our type C and A vehicles.

Herbert Mehnert, VP of engineering, Thomas Built Buses


April 2013

by Eric Butterman, ASME.org