How Heavy is Too Heavy? Idle Reduction Equipment Impacts Weight Limit Restrictions

Question of the Month: What are the state weight limits for heavy-duty vehicles on interstate highways? What weight limit exemptions exist for vehicles equipped with idle reduction technology?

Answer: Under federal law, no vehicle weighing more than 20,000 pounds (lbs) on one axle, 34,000 lbs on a tandem axle, or 80,000 lbs overall may access federal interstate highways (e.g., Interstate 70, which runs across the country from Maryland to Utah), regardless of where they get on the highway. States must enforce these requirements, or they may not be eligible for federal highway funding. However, the U.S. Department of Transportation (DOT) allows states to offer weight-limit exemptions for heavy-duty vehicles (HDVs) with on-board idle reduction technology.

Please note that states may set their own weight restrictions for roads that start and end within their boundaries, but we will focus on interstate highway requirements here.

Idle Reduction Technologies
Federal regulations allow states to adopt weight exemptions for auxiliary power units (APUs) or other qualified technologies that reduce fuel consumption and tailpipe emissions from engine idling. APUs are portable, vehicle-mounted systems that provide power for climate control and electrical devices without idling. For long-haul trucks, these systems typically have a small internal combustion engine (usually diesel) equipped with a generator to provide electricity and heat. Other on-board idle reduction technologies include automatic start-stop controls, energy recovery systems, fuel-operated heaters, coolant heaters, and battery-electric and thermal-storage air conditioners.

State Weight Exemptions
States may permit HDVs equipped with idle reduction technology to exceed the specified weight limit by up to 550 lbs to compensate for the additional weight of the equipment. The allowance was previously 400 lbs, but the federal Moving Ahead for Progress in the 21st Century (MAP-21) legislation, enacted in 2012, increased it to 550 lbs.

States must enact a law or institute an enforcement policy with their own exemptions to reflect this increased weight allowance. A map of State Recognition of the Auxiliary Power Weight Exemption to Gross Vehicle Weight is available from the U.S. Department of Energy's Office of Energy Efficiency and Renewable Energy (EERE). As the map shows, many states have not updated their laws and enforcement policies to reflect the increase in the federal allowance to 550 lbs, which means the exemption is still limited to 400 lbs. There are also six states where the exemption is not permitted at all.

States must require HDV drivers to demonstrate eligibility for vehicle weight limit exemptions. For example, drivers may need to have paperwork on hand that verifies the weight of the idle reduction equipment and be able to demonstrate that it is functional. Requirements are different from state to state.

More information on these state weight limit exemptions is also available on the Alternative Fuels Data Center (AFDC) Laws and Incentives database. The Advanced Search options allow you to identify specific exemptions by location, technology/fuel type (idle reduction), incentive/regulation type (exemption), and user-type (vehicle owner or driver). Each description of a state idle reduction weight exemption includes a reference to the applicable legislation or policy.

Refer to EERE's National Idling Reduction Network News and Argonne National Laboratory's Idle Reduction Tools and Outreach Materials for more information on idle reduction technologies and state vehicle weight limit exemptions for this equipment.

41% of U.S. public transit buses use alt fuels, hybrid technology

SunLine launched its 100% CNG (Natural Gas Fleet including all support vehicles) in May 2004 by converting from diesel! It was reported to be the first in the nation and has been leading the way ever since.

"APTA's latest research shows that 41.3% of U.S. public transportation buses were using alternative fuels or hybrid technology as of January 1, 2014."

Fueled By Oil And Natural Gas – Now And In The Future

Ron Nickelson
Managing Partner at EPL Global


The U.S. Energy Information Administration’s (EIA) new Annual Energy Outlook for 2015 contains a number of stats and projections, but you could boil them down to a couple of important points.

• Oil and natural gas are and will continue to be the foundation of an all-of-the-above energy approach that’s key to continued U.S. economic growth, energy security and overall security.
• Domestic output is and will continue to reduce U.S. dependence on imported energy. EIA says strong growth in domestic oil and natural gas production from shale and other tight rock formations, coupled with modest demand growth after 2020, will result in declining imports.

The revolution in U.S. oil and natural gas production has provided an incredible boost to workers and consumers here in America. The latest federal forecast shows that U.S. production can remain strong, despite the downturn in prices, but an all-of-the-above energy policy will be critical to our competitive edge in the decades to come. We need more energy – not less – especially as natural gas plays a rapidly growing role in America’s energy mix and domestic oil production continues to replace imports.

Spring 2015 Fuels Fix

Yale Climate Opinion Maps

Go here to see the results of a survey of public opinion on climate change. The responses are mapped out by state, congressional district and county. They questioned beliefs, risk perceptions and policy support.

They found that 63% of the respondents believe that global warming is happening. At the other end of the scale, 57% do not believe that global warming is harming people in the U.S. now, and 55% believe that global warming will cause them little to no personal harm.

On the positive side, 77% support funding research into renewable energy sources.