What Behaviors Constitute Idling?

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When talking about idling, it's important to understand what actions taken by drivers are considered idling. Idling does not include being stopped in traffic or at a traffic signal, but rather conscious activities that involve keeping an automobile engine running when the driver has no intention to start the vehicle in motion.

Commercial Trucks

Long-haul tractor-trailer operators frequently will run their engines, both overnight and during the workday. The reasons behind these actions may vary, but the end result remains the same: a vehicle dumping unnecessary pollutants into the air.

Overnight Idling

  • Trucks are kept running to:
  • Heat and cool the cab and sleeper
  • Mask noises
  • Keep the fuel warm in winter
  • Avoid cold starting
  • Provide for personal safety

Long-haul trucks typically idle six hours per day, or 1,830 hours per year, but actual practice varies, from idling one to two nights per week to hardly ever turning the engine off.

Workday Idling

Heavy-duty vehicles idle during the workday for a variety of reasons. These can include driver and passenger comfort, engine warmth, and the need to power electronic equipment or work machinery. Buses, locomotives, and marine vehicles can idle for similar reasons.

Passenger Cars and Trucks

Workday Idling

Light-duty vehicles include passenger cars, livery vehicles such as taxicabs and limousines, pickup trucks and small vans, and police cruisers. These vehicles typically idle for passenger comfort, engine warmth, and to provide power for accessories and electronic equipment.

Medium-duty trucks encompass courier and package delivery trucks and utility trucks, and they typically idle for the same reasons as light-duty vehicles. Medium-duty truck idling may be of short or long duration, depending on the reason(s) for it. In some cases, these vehicles idle to support power take off for utility equipment such as lift buckets, pumps, or lighting being used by crews in the air or underground.

Why People Idle

  1. Lack of awareness. Most of us are simply unaware excessive idling is harmful and wasteful.
  2. Perceived as necessary. Decades ago, people were taught that it was necessary to idel for proper engine warm-up (prior to the advent of fuel injection in the 1980s, carburetor-equipped vehicles needed more warm-up time to prevent the possibility of stalling in traffic). Despite the advent of fuel injection and other technologies that have generally eliminated the need for extended idling, the myth persists that warming up is good for the engine when the exact opposite is true. For modern vehicles, once the oil has circulated throughout the engine (usually 30 seconds or less), it is best to drive the vehicle to complete engine warm-up and to allow other mechanical components to warm up as well.
  3. Optimal comfort. In the spatial environments of our homes and vehicles, we naturally tend to be accustomed to keeping our bodies in a comfort zone. A fully warmed-up or cooled down vehicle cabin achieves this goal. But there is a high price - especially collectively - to be paid for prolonged warm-up idling, using remote vehicle starters or sitting in a parked idling car to keep warm or cool.

How People Idle

  • Waiting for passengers
  • Stopping at railway crossings
  • Road construction zones or border crossings
  • Running quick errands
  • Sitting in drive-through lanes
  • Waiting to refuel or to have the car washed
  • Stopping to talk to an acquaintance or friend
  • Sitting in a car while using a smartphone/mobile device
  • Preparing to leave the house (warming up)