Diesel Idling

Idle Reduction Technologies for Trucks

A large amount of truck idling occurs at travel centers while drivers rest during layover periods. Engines are idled to maintain comfortable temperatures while resting or to provide power for televisions, refrigerators, microwaves, etc. Technologies are available that can provide for these needs without engine idling. 

Examples of these fuel saving technologies are:

  • Automatic Shut Down/Start Up Systems - electronic diesel engine shut down after a set time period
  • Battery - keeps the inside of a vehicle cab warm in the winter or cool in the summer
  • Auxiliary Power Unit or Generator Set - provides heat and air conditioning for the cab
  • Electrified Parking Spaces - electric shore power connectivity can provide heat, air conditioning, and electrical power without requiring the engine of the truck to idle

SmartWay Transport Partnership

Truck technologies that save fuel or use fuel more efficiently can pay for themselves through fuel savings. The Environmental Protection Agency SmartWay Calculator helps truck owners and fleet owners compare the costs and estimate the fuel savings associated with various efficiency technologies.

Diesel Idling Restriction Ordinance

The purpose of Ordinance P-21 is to protect public health and the environment by reducing emissions of toxics and criteria pollutants while also conserving fuel. Diesel vehicles are not allowed to idle longer than five minutes under most circumstances. The ordinance applies to diesel-fueled motor vehicles weighing more than 14,000 pounds and operating in Maricopa County, regardless of where the vehicles are registered. It applies to vehicles designed to operate on public highways and powered by a diesel engine.

Penalties for Non-Compliance

The driver of the vehicle who violates this ordinance is subject to a minimum civil penalty of $100.00 for the first violation and $300.00 for a second or any subsequent violations.

Exceptions to the Idling Restrictions

  • Drivers stuck in traffic due to congestion or weather issues.
  • The main engine is being idled during Department of Transportation mandated rest periods (US 49 CFR Part 395, AZ R17-5-202).
  • The main engine is being idled in order to conform to the manufacturer's "warm up" or "cool down" specifications.
  • The main engine is being idled for maintenance or diagnostic purposes.
  • The main engine meets ALL of these listed criteria:
    • Provides a necessary power source for mechanical operations other than propulsion
    • Involves a Power-Take-Off (PTO) mechanism
    • Powers the:
      • Loading/unloading of cargo
      • Mixing or processing of cargo
      • Temperature control of cargo
      • A mechanical extension to perform work functions
  • Passenger buses (including school buses), which are being idled in order to provide heat or air conditioning necessary for comfort/safety may idle for up to:
    • 30 minutes during any 60 minute period
    • When temperatures exceed 75 degrees Fahrenheit, a passenger bus is allowed to idle up to 60 minutes during any 90 minute period
    • For emergency and/or law enforcement purposes

Report Diesel Idling Violations

To report a suspected idling violation, use our Air Quality Violations Report form.

Page reviewed 29 September 2023