Truck Idling: Causes, Effects, and Prevention

Truck engine idling consumes an estimated three billion gallons of fuel every year. This fuel consumption, when a commercial truck engine is left to run for a sizable amount of time, produces a great deal of air pollution. In fact, the Environmental Protection Agency (EPA) reports that truck and locomotive engine idling emits 11 million tons of carbon dioxide annually, along with 200,000 tons of oxides of nitrogen and 5,000 tons of particulate matter – an enormous number of pollutants for the sake of inactive transit systems.
No Idling Sign Act 124 of 2008
Many states have varying regulations on truck idling, such as this sign enforcing Act 124 of 2008.
In addition to harming the environment, long-duration engine idling also takes a heavy economic toll on drivers and fleet owners. Research suggests that most trucks idle from six to eight hours a day, 300 days a year. Per truck, that’s an added $6,000 in fuel costs each year for immobility. In addition to being economically unsustainable, engine idling for lengthy periods can result in the development of health complications for truckers. The EPA recently funded a study on the levels of air pollutants, both inside and outside of the truck, that result from idling. The study found that in-cab particulate matter concentrations far exceed the USEPA ambient air quality standards, as do the dangerous levels of nitrogen dioxide. Another similar study suggests that these contaminants are more prevalent at night, meaning that truck idling poses more of an environmental and health risk than does daytime traffic flow.
The Reasons for Idling
One of the main reasons that commercial vehicles so commonly idle is to provide drivers climate control comfort. By leaving the engine running, the truck’s HVAC systems remain operational in hot and cold weather conditions. A running engine also provides electricity for truck appliances, such as refrigerators, televisions, and microwaves.
In addition to driver comfort, long-haul truckers endure a lot of waiting time. Between waiting to make deliveries, waiting at border crossings, and waiting to pick up loads for delivery, the amount of time a commercial truck spends immobile can be immense.
Perhaps the main factor behind engine idling is the safety-related Hours-of-Service regulations at the Federal Motor Carrier Safety Administration. These requirements limit the number of consecutive hours for which commercial motor vehicle drivers are permitted to drive, essentially mandating minimum rest periods, during which drivers frequently let the car idle before getting back on the road.
State and Local Regulations on Truck Idling
Because truck idling is so detrimental to the environment, a growing body of state and local regulations now limit the practice. Part or all of over 28 states, including the District of Columbia, enforce idling regulations. A cumulative effect of local regulations on idling has proven effective, effectively creating a network of jurisdictions through which truckers pass to deliver goods. These laws generally limit idling time and levy a civil or criminal fine for failure to comply. These fines tend to be small, but some jurisdictions allow for fines as large as $25,000 to $50,000, plus potential time in prison.
Improved Technology: The Road to Legal Compliance and Energy Efficiency
An emerging industry around idling has introduced commercial technologies designed to reduce infractions of these regulations, while protecting both the economy and the environment from the side effects of idling, which are direct results, most often, of fuel consumption and engine wear. Some of these commercially available technology options include:
• Automatic engine shut down/start up (locomotive): An automatic engine shut down/start up system controls the engine by stopping or starting it without operator action, based on a set time period or ambient temperature, and other parameters (e.g., battery charge). • Fuel-Operated Heaters (truck only): These are small, lightweight heaters that burn fuel from the main engine fuel supply or a separate fuel reserve. They provide heat only and can be used in conjunction with cooling systems depending on comfort needs. • Diesel-Driven Heating System (locomotive only): Designed to heat both coolant and oil to allow for main engine shutdown in cold temperatures, the diesel-driven heating system does not use a generator to produce auxiliary power. Instead, it circulates and heats the engine coolant and oil toward a target temperature of 120 F. • Auxiliary Power Units/Generator Sets (truck and locomotive): These are small, diesel-powered engines (5 to 10 horsepower) that are installed on the truck to provide air conditioning, heat, and electrical power to run accessories like lights, on-board equipment, and appliances. • Electrification: Electrification refers to a technology that uses electricity-powered components to provide the operator with climate control and auxiliary power without having to idle the main engine. This can take the form of on-board equipment, e.g., power inverts, plugs; off-board equipment, e.g., electrified parking spaces or systems that directly provide heating, cooling, or other needs; or a combination of the two.
Idling Reduction through Behavior Change
While technologies aid in the reduction of truck and locomotive idling, direct action may be a more effective solution for idling. Some behavioral methods currently in place to reduce idling include state and local policy, driver/operator training, and financial incentives.
State and Local Policy: Over 22 states restrict the amount of time that a vehicle’s main engine can be idle. The American Transportation Research Institute (ATRI) has a complete list of state and local laws on truck idling.
Driver/Operator Training: One of the most effective ways to reduce idling is through education. Educating drivers and operators about the adverse impact of long-duration idling can help change their behavior on the road.
Financial Incentives: Fleet owners can offer financial incentives to drivers to reduce idling. Many large trucking companies already offer these incentives, and have reported idling times below national averages.
Despite these measures, instituting a “no-idling” policy or educating drivers may not be enough to deter a driver or operator from letting the engine idle in extreme weather conditions. That’s where technology solutions come into play.
State Idle Reduction Incentive Programs
Idle reduction systems are generally very cost effective in terms of payback periods, yet many small truck fleet owners and operators lack ready access to the capital it takes to retrofit their vehicles. In an effort to address this concern and promote better idling practices, a growing number of state programs provide grant funds or financing to assist truck owners and operators in retrofitting their trucks to comply with applicable laws.
Idling Sign with Graphic
Universal graphics on signage, such as the one above, help to convey the no idling message.
Truck idling is a costly and environmentally unsustainable commonality throughout the United States and the world at large. Along with the very many reasonable causes for truck idling, there also exists an equally ample number of solutions, both technological and behavioral. These make for a more environmentally and economically friendly way to maximize comfort for drivers while they’re inactive.

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