Why do semi-trucks idle? Understanding impacts and alternate options

Estimated reading time: 2 minutes

In the past, truck drivers would leave their engines running during rest periods (a method known as idling) to keep their cabs comfortable and power their electronics. This outdated practice, however, burns extra fuel, wears on the engine and increases emissions.  

At Schneider, we’re committed to reducing emissions and leading the industry in sustainable practices. One of the many ways we do this is by implementing technology and practices that reduce the need for drivers to idle.

Keep reading to learn more about why drivers idled so much, and what companies like Schneider do to eliminate the need for it. 

Why did some truck drivers idle?

For many truck drivers, the cab of their semi-truck is a home away from home. It’s their office, kitchen and bedroom all in one. Idling their engines while they are on break served a few practical purposes that ensured their comfort and the truck's readiness:

Maintaining a controlled climate

In the past, idling was the only way for drivers to regulate the temperature inside the cab. In the cold of winter or the heat of summer, the truck's engine powered the heating and air conditioning systems. This allowed drivers to get the rest they need in a comfortable environment. 

Keeping the engine warm

In extremely cold climates, idling can prevent the engine's fuel and fluids from gelling or freezing. Keeping the engine warm helped ensure the truck would start without any issues when it was time to get back on the road.

Preventing a dead battery

A semi-truck's battery system powers more than just the engine. It runs lights, radios and any personal appliances the driver uses, like a refrigerator or a phone charger. Idling kept the batteries charged, ensuring the driver could power these necessary devices without worrying about dead batteries.

What are the downsides of idling?

While necessary for some drivers, overnight idling has a number of negative consequences:

Fuel consumption and cost

Just how much fuel does a semi-truck burn idling? When idling, a semi-truck can burn approximately 0.6 to 1.5 gallons of fuel an hour. So, if a driver idles for eight to 10 hours overnight, that adds up to a large expense over the course of a year.

As an example:

• A driver idles for 10 hours overnight.
• Fuel costs $3.50 per gallon.
• His truck burns 1 gallon of fuel per hour.

That driver will spend $35 per night to idle their truck.

Engine wear and tear

Extended idling is also hard on the truck's engine. This excess use can result in:

• More frequent maintenance.
• Higher repair costs.
• A shorter engine lifespan.

Aftertreatment and emission controls

Idling is especially hard on the aftertreatment system. Long periods of idle will almost certainly result in fault codes and derates.

Environmental impact

The environmental toll of idling is substantial. Because of this, many states have regulations on how long a semi-truck can idle due to environmental concerns. Fines for excessive idling can range anywhere from hundreds to thousands of dollars.  

What are the alternatives to idling?

While some drivers with older, outdated trucks have to idle their truck while they’re stopped, it is unnecessary for drivers with newer, more upgraded equipment.  

New systems allow drivers to stay comfortable and keep their devices charged without the cost and environmental impact of idling. Some of the features Schneider specs its trucks with to prevent the need to idle, include:

Optimized Idle

This system reduces engine idle time by automatically stopping and starting the engine when needed. The Optimized Idle system is a standard feature on Schneider’s sleeper trucks and allows drivers to:  

• Keep the engine oil temperatures between factory set limits.  
• Keep the truck battery charged.  
• Keep the cab at the desired temperature.  

Additionally, it contributes to lower overall exhaust emissions, making it an environmentally friendly solution.

Battery-powered HVAC systems

This equipment works with bunk heaters and the Optimized Idle system to maintain climate control in semi-truck cabs. Drivers can use this system to maintain their heat or air conditioning while they sleep without having to regularly start their engine.