Propane Buses: Safely Bringing Students to School

School buses fueled by propane autogas offer a wide range of benefits and are a gallon-growing opportunity for propane retailers.

The top American school bus manufacturers—Blue Bird, IC, and Thomas Built—all sell propane autogas school buses. The Propane Education & Research Council (PERC) reports there are nearly 13,000 propane school buses operating in 700 school districts. These buses transport more than 700,000 students across North America. Propane now makes up about 45% of all non-diesel school buses used for pupil transportation.

That’s about 675 million gallons of propane being consumed over the lifetime of the existing buses on the road.

With more school districts looking to stretch budgets and make “greener” choices, opportunities for the propane bus market expansion are abundant. Highlighting the environmental and economic sustainability as well as the safety of this alternative fuel is key to converting school districts into propane customers.

School buses are the safest mode of transportation for getting children to and from school. In fact, school buses represent 25% of the miles traveled by students, but account for less than 4% of the injuries. In addition, every school bus in service takes about 36 cars off the road, resulting in less traffic congestion and a reduced carbon footprint.

There are many safety components to propane, specifically when used in transportation. Cleaner air, quieter operation, and low flammability top the list of propane bus safety benefits.

As noted by the Propane Education & Research Council (PERC), students riding in propane autogas buses aren’t exposed to diesel exhaust’s harmful particulate matter, which can aggravate asthma and is a known carcinogen.

Operating at 11 decibels lower than diesel vehicles, autogas buses are noticeably quieter. School bus drivers around the nation report that reduced noise allows them to better serve students.

“Propane buses are extremely quiet, which plays a role for our drivers and students on the bus,” says Pat Mitchell, director of transportation at the Mobile County Public School System in Alabama. “Our drivers can hear more and be more aware of what is going on inside the bus instead of trying to hear over a loud diesel engine.” Dave Anderson, transportation director at Adams 12 Five Star Schools in Colorado, agrees. “You can hear [the passengers] and they can hear you,” he says.

Propane has a very narrow flammability range: a specific set of circumstances—air/fuel ratio, temperature of the ignition source, etc.—is required to ignite the fuel. Propane autogas fuel systems run in a closed loop, meaning the fuel is never exposed to air and won’t spill. If a leak did occur, the propane would immediately vaporize into the atmosphere (when exposed to normal atmospheric conditions) instead of pooling on the ground like diesel or gasoline.

Propane autogas vehicle fuel tanks are 20 times more puncture-resistant than diesel tanks and can withstand four times the pressure. They are constructed from carbon steel in compliance with the American Society of Mechanical Engineers. The tank mounting systems are designed at twice the requirement specified by the National Fire Protection Association to ensure tanks remain securely attached, even in a severe collision or rollover.

All propane school buses must comply with state and federal regulatory requirements. They must meet or exceed National Highway Traffic Safety Administration and Federal Motor Vehicle Safety Standards. The engines also carry emissions certifications by the Environmental Protection Agency (EPA) and California Air Resources Board (CARB). As a nontoxic, non-carcinogenic, and non-corrosive fuel, EPA classifies propane as a non-contaminant.

For all its safety benefits over conventional fuels, a propane autogas fuel system is relatively simple in design. Using expert engineering and precision manufacturing, the bus’ entire gasoline or diesel system is replaced—from the fueling nozzle to the fuel injectors—and the powertrain control module is reprogrammed.

Propane retailers can get the message out about propane school buses by presenting at local school board meetings and to school bus contractors that may purchase buses for dozens of different school districts. A successful presentation should touch on the benefits of propane, how buses are fueled, the large number of case studies, and sources school districts can tap for advice.

Since the price of propane fluctuates with supply and demand, fleet customers purchasing thousands of gallons of propane per year can secure a more competitive price than a residential customer purchasing a hundred gallons (or fewer) per year. Most propane autogas customers lock in annual propane rates, helping them to budget fuel expenses.

On average, a gallon of propane autogas costs about 40% less than gasoline and 50% less than diesel. For example, ABC Student Transportation, a contractor for Detroit Public Schools, pays 75% less per gallon for propane compared with diesel.

Standard diagnostic equipment can be used to service the vehicles. There is no need for additional fluids or filters, a huge advantage over diesel. Oil changes are simpler and less expensive, and there are no pricey exhaust after-treatment or diesel emissions fluids required to meet today’s strict emissions regulations. Propane-fueled buses eliminate the need for particulate trap systems, turbochargers, and intercoolers. Filter packages cost about 60% less for propane autogas buses than diesel buses.

Comparing the total cost of ownership between diesel and propane buses can also help school districts and contractors make a more informed decision. As a rule of thumb, the higher the annual miles driven and the lower the fuel efficiency, the more likely propane will provide a quick return on investment. Both ROUSH CleanTech and PERC have online cost calculators at ROUSHcleantech.com and propane.com/on-road-fleets/calculator to help schools estimate their savings.

When compared to conventional diesel buses, fueling with propane autogas results in an estimated 80% reduction in smog-forming hydrocarbon emissions and virtually eliminates particulate matter. By replacing all diesel school buses older than model year 2007 with new propane autogas buses, school districts can reduce their nitrous oxides (NOx) emissions by more than 92%.

Switching school buses from pre-emission-regulated diesel to improved clean technology decreases particulate and gaseous air pollutant and toxic emissions during transit, pick-up, drop-off, and idling.

The ROUSH CleanTech 6.8-liter V-10, 3-V engine, equipped in Blue Bird Vision Propane buses, has the lowest NOx levels of any propane autogas engine in Class 4-7 vehicles. The engine is certified below the optional low NOx standard of 0.05 g/bhp-hr set by CARB. In terms of NOx emitted, for every one bus at the 0.2 NOx standard, there can be four buses on the road at the .05 level.

As previously noted, propane autogas buses reduce noise levels by about half compared to a diesel engine. PERC has many resources that explain the benefits of reduced noise at propane.com/on-road-fleets/quieter-school-buses.

The most popular fueling choice for school districts is an on-site, private fueling station that allows buses to refill as needed. Route buses that come and go from a central location typically make the most sense for school districts, and create a natural hub for refueling. Propane suppliers can guide school districts in choosing the right equipment based on fleet size, routes, budget, and facility space.

A key factor for school districts is budgeting. Propane autogas fueling infrastructure is affordable, costing less than any other fueling station—conventional or alternative. Plus, no modifications are required if the facility is already code-compliant for conventional fuels.

Another option is for propane providers to perform on-site propane autogas fueling services. Both Boston Public Schools and Florida’s Hillsborough County Public Schools rely on local propane providers to supply mobile on-site fueling for their fleet of propane buses.

For many school district administrators, making the recommendation to a board or school bus contractor to buy propane-powered school buses may come with questions and scrutiny. Adopting an alternative fuel can seem daunting.

Encourage decision-makers to talk to their peers in neighboring areas that operate on propane to see how propane buses work for them. With propane-powered school buses running in almost every state in the U.S., there are sure to be many nearby. Check your region by using PERC’s online map at propane.com/busmap.

Other online sources to review include case studies at propaneschoolbuses.com and ROUSHcleantech.com/testimonials. Information is also provided by the Alternative Fuels Data Center at afdc.energy.gov.

School buses fueled by propane autogas have accumulated hundreds of millions of miles on today’s roads. That’s a lot of propane purchased and consumed. What are you waiting for?

Todd Mouw is vice president of sales and marketing at Livonia, Mich.-based Roush CleanTech, an alternative fuel vehicle technology company. Mouw has served as president of the NTEA Green Truck Association. Reach him at

or 800/59ROUSH (800) 597-6874. To learn more, visit ROUSHcleantech.com.