The Boulder Valley School District faces a conundrum in school bus transportation. Despite its commitment to reach carbon neutrality by 2050, the district board approved spending $715,000 to buy five new diesel-powered school buses Tuesday.

Materials provided to the Board of Education showed diesel school buses are “essential for mountain routes due to their robust performance in challenging terrains. These routes often have steep inclines, variable weather conditions, and remote locations, making diesel buses a practical choice.”

Propane and electric buses have limitations on mountain, background materials in the agenda showed.

“Propane can struggle with altitude and extreme cold, while electric buses experience reduced range in hilly areas and require frequent recharging, making them less reliable for these specific routes. Diesel buses remain a reliable choice for ensuring safe transportation for students in mountainous regions.”

Rob Price, assistant superintendent of Operational Services for the district, pointed out an important safety aspect of diesel school buses.

“Due to the mountainous terrain that we travel in, when descending, diesel buses have a compression braking system that propane and electric buses don’t have, and that is a requirement of CDE (Colorado Department of Education), so it’s for safety concerns,” said Price.

Diesel buses, Price said, also have more than three times the range of electric buses.

“Our mountain buses have a range of about 350 miles,” he said. “Propane buses have a range of about 250, and our electric buses only have a range of about 120.”

Randy Barber, chief communications officer for the district, told The Denver Gazette the district currently has 133 diesel, 53 gasoline, 46 propane, and six electric school buses — with another three electric buses on order.

The district keeps the electric buses on shorter routes in the flatlands., Barber said.

The district has three transportation hubs in the county, but Barber expressed some concerns with the availability electric vehicle (EV) bus chargers and the infrastructure needed to serve them.

Of diesel buses Price said: “We would like to get away from them. However, we do not have the technology currently at our disposal to get away from diesel buses for these longer trips and for the mountainous terrain in our district.”

“We want to be more environmentally conscious, and our goal is to have more electric vehicles, but we have to consider what’s needed,” Barber said. “There’s a difference between ambition and where we’re at.”