Truck and Bus Engine Idling (primarily diesel)


The business community is a key in the goal of eliminating unnecessary vehicle idling. Vermont, despite being a small state, has many fleet operators with truck, bus and car fleets. Registered in Vermont are more than 20,000 trucks, more than 15,000 of which are diesels. Diesel engines are durable and economical sources of power. But, unless they contain the newer EPA mandated tighter emissions controls, they are significantly more toxic than gasoline engines, emitting pollutants such as particulate matter (commonly known as soot), nitrogen oxides (NOX), and volatile organic compounds (VOC). See The Health Impact: What's in Diesel Exhaust? below and visit the Idling Facts page to learn more about the health impact of diesel exhaust.


Medium- and heavy-duty vehicles, most equipped with diesel engines, need not idle for extended periods of time. Reducing idling yields benefits in avoiding fuel use and engine wear that increase company profits, improve health, conserve energy, mitigate climate change, and comply with state laws and client rules.

The math on fuel use of extended idling by trucks and buses


While there are some legitimate reasons trucks and buses need to idle, in many instances excessive idling can be avoided. Even with recent lower fuel costs, it still makes sense to break the unnecessary idling habit. Remember that idling gets 0 miles to the gallon. How much does it cost to idle medium- and heavy-duty vehicles? More than you think. The larger the fleet, the more profit goes through the exhaust pipe. A heavy-duty vehicle burns about one gallon an hour. If that vehicle idles unnecessarily for two hours a day, with diesel at $2.75/gal., it will cost more than $1,400 annually (260 day year). If you have a 25 truck heavy-duty fleet, the annual cost will be around $35,000. Plus, add half again to these costs for all vehicles idling excessively due to increased engine maintenance and shortened engine life.


Click on the table above to see the math on the fuel use of extended idling.


Engine manufacturers on idling fuel economy and engine wear


Caterpillar Inc. "How much is idle time costing you" document states, "Turn off trucks

  that are waiting more than 5 minutes to load or unload." and "Restrict morning warm-ups

  to 3 to 5 minutes."

Caterpillar Global On-Highway representative states, "There is no additional wear

  when shutting the truck on/off several times a day. There are benefits in fuel economy

  and wear/durability when shutting the truck down rather than idling."

Cummins Inc. MPG Guide states, "...avoid unnecessary engine idling. The vehicle gets

  its worst mpg when the engine runs and the truck doesn’t move. Every hour of idle time

  in a long-haul operation can decrease fuel efficiency by 1%."

Daimler Trucks North America/Freightliner Trucks: "The belief that idling a diesel engine causes no engine

  damage is wrong. Idling produces sulfuric acid, that is absorbed by the lubricating oil, and eats into bearings,

  rings, valve stems, and engine surfaces."

Detroit Diesel notes that along with other fuel-efficient habits, it’s critical to educate drivers on the role of

  shorter idle times. “Optimizing driver habits alone can improve fuel economy by up to 30%”.

• IC Corporation's engine manual states that "...Excessive idling reduces fuel economy,

  and may decrease oil life."

Kenworth Truck Co. representative states, "Starting and stopping the engine is actually easier on the

  engine than prolonged idling."

Navistar/International Trucks: "When a truck is stopped and idling, it is achieving zero miles per gallon. In

  fact, it burns through about a gallon per hour, decreasing overall fuel economy by 1 percent." "Unnecessary

  idling increases cost of ownership and also results in excessive engine wear and additional pollution."


TECHNICAL FACT SHEET: Oil Contamination / Fuel Dilution, Turbocharger Cool Down, and Starter Wear


What about truck regenerations?


To meet EPA emissions standards, newer trucks come equipped with emissions controls making them up to 90% cleaner than older diesels. This includes a diesel particulate filter (DPF) which must be regenerated to keep doing its job.


1. Under normal duty cycles, DPF regeneration occurs passively or automatically while the vehicle is driven, and the driver doesn’t do anything differently.

2. If a vehicle is not being operated under a normal duty cycle — lots of short stops and starts, excessive idling, etc. — a warning light will come on indicating that the DPF needs to be regenerated. The driver has two options – A) do a manual or forced parked regeneration, or B) drive the vehicle normally (40 MPH or more for about 20 minutes) and the regen will occur automatically. A common misunderstanding is that many drivers and fleet operators are not aware of option B.

3. To minimize fuel wasting parked regens, operate the vehicle as it was designed: normal duty cycles whenever possible, and minimizing idling. The more idling, the more parked regens required.

THIS VIDEO BY CUMMINS fully explains regenerations.


The health impact: What's in diesel exhaust?


• Particulate Matter – [PM]: Linked to cancer, respiratory disease, cardiovascular disease and increased respiratory illness in children and the elderly.

• Nitrogen Oxides – [NOX]: Linked to problems such as shortness of breath, asthma, respiratory disease and decreased lung function.

• Carbon Monoxide – [CO]: Reduces the flow of oxygen in the bloodstream and is of particular concern to those with cardiovascular disease.

• Hydrocarbons – [HC]: When combined with nitrogen oxides in the presence of sunlight, hydrocarbons can irritate the eyes, damage lungs and aggravate respiratory problems


While diesel exhaust is particularly harmful for children and the elderly, it also has a major impact on trucking industry workers. The Department of Labor Occupational Safety and Health Administration has published a Hazard Alert for Diesel Exhaust/Diesel Particulate Matter providing details of the health impact of diesel exhaust across a large number of industries including mining, transportation, construction, agriculture, maritime, and many types of manufacturing operations, and how exposures can be controlled.


Gasoline emissions are significantly less toxic, but they also contain harmful chemicals including hydrocarbons, nitrogen oxides, and carbon monoxide.


While the EPA has mandated tighter emissions rules in 2007 on ultra-low sulfur diesel engines, which have much lower toxic emissions, most of the current fleet of heavy-duty diesel vehicle emissions remains uncontrolled. These older vehicles are expected to remain in operation for decades to come.


Idling and the law


There are laws in Vermont and other states that limit the idling of motor vehicles.

Vermont's Prohibited Idling of Motor Vehicles law limits the idling of all motor vehicles while parked to five minutes in any 60-minute period, with exceptions. The rest of the New England states, as well as New York and other states have laws or regulations limiting the idling of vehicles.

Vermont’s Unattended Motor Vehicle law prohibits the idling of all motor vehicles while unattended in public. If you leave your vehicle, you must shut it off.

• The city of Burlington’s ordinance has a 3 minute idling maximum while parked.

• Vermont has a school bus idling rule that prohibits the idling of school buses on school grounds while students board or exit the bus.

Strategies, technologies, and devices that help reduce fleet idling


How do companies like CCNNE, FairPoint and many others successfully reduce their idling? Driver behavior and compliance is most important and formal policies go a long way in guiding them in the right direction. But devices and systems that monitor idling and actually restrict it can help achieve maximum effectiveness in idling reduction with reasonable ROI. Some of these are:


Telematics: Many fleets (including CCNNE and FairPoint) utilize telematics (chiefly the application of GPS tracking) to monitor the data of vehicle operations — including idling — in passive or real time. These systems are largely effective and typically pay for themselves within a year in idling reduction and other operational efficiencies.


Auto shutdown: Automatic Engine Shutdown Systems start and stop the truck engine automatically to maintain a specified cab temperature or to maintain minimum battery charge. Drivers can also program the system to shut down after a specified period of idling time. In many circumstances, however, drivers can shut down immediately.


Battery powered systems: Vehicle systems that provide heating, cooling, or other specialized services and are powered by batteries instead of idling. Companies such as GRIP Idle Management System offer these power management systems for many types of fleet applications including law enforcement, ambulance/ems, service, hydraulic, and long haul.


Block heaters: A "no-brainer" in colder climates, block heaters help warm the engine to avoid starting difficulties and reduce stationary warm-up times.


Refrigrerated units: Refrigerated trucks equipped with reefer units (such as Thermo King and Carrier) do not need to idle the primary engine for cooling purposes during deliveries.


Long haul: Systems such as Auxiliary Power Units (APUs), Truck Stop Electrification and Fuel Operated Heaters can eliminate or greatly reduce overnight idling. They vary in paybacks of six months to eighteen months.


In 2011, UPS delivery drivers in telematics-equipped vehicles eliminated more than 98.0 million minutes of idling time. Telematics use helped saved more than 653,000 gallons of fuel (and avoidance of 6,470 metric tonnes of CO2).

What about adopting an idling reduction policy?


A real win for businesses is to adopt a formal, written idling reduction policy. Not only do drivers and operators better comply with an official policy, but the company's social responsibility and "green" image is enhanced. And, of course, the resulting avoidance in fuel use and engine wear leads to increased profit. For municipal fleets, town residents will appreciate knowing that their town employees are saving taxpayer dollars, improving health, conserving energy and lessening the town's carbon footprint. See the approximately 35 Vermont fleets that have already adopted policies.


Download: Sample policy in Microsoft Word format that can be tailored to your fleet's operation.


How do idling reduction policies work? Fleet size doesn't matter - two or 1,200. Look over the sample policy and the two examples below.

Coca Cola Bottling of Northern New England




CCNNE operates in northern New England with a fleet of 1,000 vehicles total; 94 in Vermont. In 2005, CCNNE adopted an idling reduction policy to improve the environment, reduce its carbon footprint, and save fuel.


FOR VERMONT ALONE: 2004 to 2010 results:

2004 (15% Idle time = 18,012 gal. of diesel)

2010 (5% Idle time = 4,519 gal. of diesel)

Annual reduction of 13,493 gal. diesel/yr.

One gal. of diesel emits 22.4 lbs./gal. of CO2

Annual reduction of CO2 302,243 lbs./yr.

Diesel cost savings @ $4.00/gal. = $54,000/yr.


Download: CCNNE's Idle Reduction Plan PowerPoint presentation

Fairpoint Communications Northern New England

(Note: Consolidated Communications acquired FairPoint in 2017)




FairPoint partnered with the American Lung Association and Idle-Free VT in 2011 to reduce the idling of its 1,200+ vehicle fleet after idling reduction presentations and training at company garages in Vermont.


After implementing their initiative, FairPoint's average fleet idle time was reduced from 92 hrs./vehicle in early 2011 to 54 hrs./vehicle in late 2012. Correspondingly, gas for idling dropped from 80 to 47 gals./vehicle – a total reduction of more than 40%, saving FairPoint more than $300,000! These reductions are also saving 288 metric tons of CO2 emissions annually.


FairPoint's Anti-Idling Initiative news release

FairPoint's Anti-Idling Initiative report

From the U.S. Department of Energy's Office of Energy Efficiency and Renewable Energy (EERE), Vehicle Technologies Office: NATIONAL IDLING REDUCTION NETWORK NEWS (NIRNN)

UPDATE: NIRNN ceased publication November 2016; ARCHIVES remain available.


The National Idling Reduction Network brings together trucking and transit companies; railroads; ports; equipment manufacturers; Federal, state, and local government agencies (including regulators); nonprofit organizations; and national research laboratories to identify consistent, workable solutions to heavy-vehicle idling for the U.S.