Heavy Duty Vehicles

Tractor Trailer Heavy duty vehicles are a critical component of Connecticut's economy. School buses transporting students, ferries shuttling people across Long Island Sound, and planes, trucks and trains moving freight and consumer products across the state are a few examples of how important heavy duty vehicles are to Connecticut. These heavy duty vehicles consume large amounts of fossil fuels. For the state to meet its clean air goals, we must take and support actions to optimize the efficiency of these heavy duty vehicle activities.
What is a MHD Vehicle? Watch the YouTube Video

An Assessment of Connecticut’s Need to Adopt California’s Medium and Heavy Duty Vehicle Emission Standards 

2022 MHD Report Thumbnail On December 17, 2021, Governor Lamont issued Executive Order 21-3 (E.O. 21-3), which directed state agencies to take actions to reduce carbon emissions and adapt to the climate crisis. Among those actions directed to the agencies, the Executive Order directed DEEP to “Assess the need to adopt California Medium and Heavy-Duty ("MHD") vehicle emissions standards. DEEP shall assess the need to adopt the California Air Resources Board ("CARB ") standards for MHD vehicles as part of the state's efforts to meet air quality and climate change goals.”
Today, DEEP is publishing “An Assessment of Connecticut’s Need to Adopt California’s Medium and Heavy Duty Vehicle Emission Standards” (Assessment) pursuant to E.O. 21-3.  Among its findings, the Assessment finds that adoption of California MHD standards would reduce criteria, and GHG emissions, create economic benefits, and lead to lower health care costs in Connecticut.

Download the MHD Report 

Multi-State Medium and Heavy Duty Zero Emission Vehicle MOU

Cover of MHD ZEV MOU

On July 14, 2020, Connecticut took another significant step forward in its effort to address the climate crisis and the health impacts of air pollution as it joined 14 other states and the District of Columbia in signing a Memorandum of Understanding (MOU) to work collaboratively to advance and accelerate the market for electric medium- and heavy-duty vehicles.

Under the MOU, signatory states will work toward ensuring that 100 percent of all new medium- and heavy-duty vehicle sales be zero emission vehicles (ZEVs) by 2050 with an interim target of 30 percent ZEV sales by 2030. The vehicles included in the MOU include large pickup trucks and vans, delivery trucks, box trucks, school and transit buses, and long-haul delivery trucks.

The MOU provides a framework to coordinate state efforts to meet the MHD electrification goals. The signatory states will work through the existing multi-state ZEV Task Force to develop and implement a ZEV action plan for trucks and buses. The plan will identify policies and programs to inform policy makers and support the timeframes and targets specified in the MOU.

Multi-State Medium and Heavy Duty ZEV MOU

Multi-State Medium and Heavy Duty ZEV MOU - Fact Sheet

Multi-State Medium and Heavy Duty ZEV MOU - Market Readiness Materials and Findings

Press Release - State of Connecticut

Press Release - NESCAUM

CT Business & Investor Letter of Support for Medium and Heavy Duty ZEV MOU

Connecticut's Freight Strategy

Truck, Train, Shipping Boat

In 2013, DEEP commissioned a study to analyze and develop a strategy to reduce emissions from freight movement in the state. The report addresses how freight is moved in Connecticut, the emissions associated with freight movement now and in the future, and the most promising strategies to reduce the energy and environmental impacts of freight movement.

Development of a Strategic Plan for Reducing Emissions Associated with Freight Movement in Connecticut


SmartWay Logo

In 2015, DEEP became a SmartWay Affiliate. DEEP supports the goals of SmartWay and encourages you to explore the benefits of joining SmartWay.

EPA's SmartWay program helps companies advance supply chain sustainability by measuring, benchmarking, and improving freight transportation efficiency. This is accomplished by using market-based incentives and technology solutions to address long-term trends, changes and challenges in the freight transportation sector.

Find out more about SmartWay and learn how joining SmartWay can benefit your operations.

How can heavy duty vehicle emissions be reduced?

Retrofit Technologies

Retrofit technologies are products that can be installed on heavy duty engines to reduce pollution from vehicles that are typically powered by diesel fuel. The most commonly referenced retrofit technologies are diesel oxidation catalysts (DOCs), which function like catalytic converters in automobiles, and diesel particulate filters (DPFs).

EPA provides a substantial list of verified technologies that save fuel and reduce emissions.

Idle Reduction Technologies
Big Rig Trucks idling

Idle reduction technologies provide vehicles such as heavy duty trucks power for heating, cooling, and electricity without requiring the idling of the main engine. Idle reduction technologies can reduce air pollution at rest areas, truck stops, pick-up and delivery locations, ports and in other places where trucks idle for extended periods either for rest or in queues. Auxiliary power units (APUs) and truck stop electrification (TSE) are some of the ways idling can be reduced.

In addition, Connecticut has strict laws limiting the time a vehicle can idle. Find out more about our idling law on our anti-idling webpage.

Repower, Repair, Rebuild, or Replace

As heavy duty engines age, they become less efficient and more costly to maintain. A decision to repair, replace, or rebuild an engine is a difficult one to make, but federal and state funding programs like the Diesel Emissions Reduction Act (DERA) and Connecticut's VW Diesel Emissions Reduction Program are available to make this decision easier.

Maintenance and Cleaner Fuels

The simplest way to minimize emissions from heavy duty vehicles is to ensure they are properly maintained. This optimizes fuel economy and life of the engine. Emissions can be further reduced by operating on ultra-low sulfur fuel or biodisel blends if the engine is capable of utilizing these fuels.

Connecticut's Heavy Duty Emissions Reduction Projects

Large Dump Truck

DEEP’s funding efforts since 2008 have leveraged millions from the state and national DERA, the Federal American Recovery and Reinvestment Act (aka Stimulus Act) and the Connecticut Clean School Bus Act to reduce heavy duty diesel emissions that impact both the environment and residents of the state.

Explore the history of our efforts and wide range of projects funded on our diesel emissions reduction project archive.

Content last updated August 11, 2020