Fleet efficiency

Transportation Case Study
Feb. 16, 2010

Retrofitted school buses save fuel, electricity, time, emissions

Last winter, the seven buses for Garfield County School District 16 routes each idled 15 to 20 minutes on school mornings, creating a blue cloud of exhaust in an area by the Colorado River already prone to inversions.

“This year, we start our buses and there are no discernable particulates going up in the air; no more blue cloud,” said Linda Cannizzaro, transportation coordinator for the district, which serves Battlement Mesa and Parachute.

The District 16 vehicles are among 99 school buses in Garfield and Rio Blanco counties that were retrofitted in mid-2009 as part of the Colorado Clean Diesel Program, said Lisa Silva, air quality planner with the Colorado Department of Public Health and Environment.

The buses received engine preheaters, diesel oxidation catalyst equipment to curtail tailpipe emissions, and/or closed crankcase filtration units to prevent engine emissions from flowing into the cabin.

Measurable cost savings from bus upgrades

Transportation managers are tracking savings in electricity, diesel fuel and staff time. Local districts are saving electricity this winter, since buses with the programmable preheaters no longer have to be plugged in to block heaters. The engine antifreeze is warmed by a preheater that uses a fraction of the fuel compared to running the engine.

Larry Estrada, Roaring Fork Re-1 School District director of transportation, reported a total of $1,678 in electricity savings for 30 buses during the month of December compared to 2008. Morning warm-up idling times for the district’s buses have been cut from 12 minutes to 6 minutes. Re-1 serves Glenwood Springs, Carbondale and Basalt.

In District 16, Cannizzaro estimates savings of up to $300 a week due to lowered fuel use and staff time.

“For our morning route, we’ve noticed that we do not have to pre-warm our buses, so we’ve cut 15 to 20 minutes off our routine,” said Cannizzaro. She estimates each bus is using 10 gallons less of diesel per week this winter.

emission-reducing equipment installed under the hood

Above, Garfield Re-2 School District bus driver Jackie Kneedler shows off emission-reducing equipment installed under the hood of the school bus she drives. Below, Kneedler shows off a new engine preheater that greatly reduces warm-up idling.
Photos by Suzie Romig

school bus pre-heater

Robert Sjogren, Garfield Re-2 School District fleet manager, said the district has realized many benefits from the retrofits. “The biggest benefit is keeping emissions out of the cabin of the bus.”

Sjogren said he sees “a visible, noticeable difference” in the amount of soot coming out the tailpipes when the buses are at operating temperatures. Buses in Re-2, which cover Rifle, Silt and New Castle, now idle a maximum of four minutes in the mornings to build pressure on the air breaks, lowered from 10 minutes last winter.

Upgrades reduce students exposure to diesel pollutants

 “The Garfield, Rio Blanco counties project will result in substantial reductions in exposure to air toxics for the student bus riders,” said  state air quality planner Silva. “Children are a captive audience, and they might ride the bus twice a day for 12 years. That’s a lot of exposure.”

Longtime Re-2 bus driver Jackie Kneedler said she is no longer receiving complaints from students being cold or smelling exhaust inside the bus.

Silva said the local retrofits should reduce the amount of harmful air pollutants at similar levels to retrofits completed earlier on buses in Pueblo. A University of Colorado study sampled the air inside the Pueblo buses before and after the retrofits and showed the overall average in cabin pollutant particles was reduced by up to 41 percent.

Ultra fine particulate matter, which is inhaled deeply into the lungs and can go into the blood stream, was lowered by an average of 56 percent. Elemental carbon, also known as soot, saw an 85 percent reduction. Formaldehyde, a combustion-related byproduct, was reduced by 32 percent.

Silva said the retrofits cost up to $4,000 per bus. She said some funding remains to retrofit 12 to 15 more buses, such as those used at private schools.

For information, contact Silva at Lisa.Silva@state.co.us.

In this section

Reducing fuel consumption cuts carbon emissions and saves money. These pages offer proven means to reduce fuel consumption in government fleets.

Carrying out recommended actions

Real-world examples of fleet efficiency:

EXAMPLE 1: Use electric or smaller gas-powered service trucks

EXAMPLE 2: Purchase efficient tires for passenger vehicles

EXAMPLE 3: Purchase hybrid passenger vehicles


Example green fleets policies


Transportation Case Studies

How Eagle County cut fleet costs and fuel consumption

Nitrogen is nifty for holding tire pressure

Compressed Natural Gas: Hatching the egg on the Western Slope

Retrofitted school buses save fuel, electricity, time, emissions


Vehicle Fleets in the Clean Energy Economy workshop
Feb. 5, 2010
Archive of presentations and meeting materials