Key Takeaways
- •Sen. Sullivan (R-AK) promoted S.3135 to permit diesel engine overrides during extreme cold, preventing automatic performance "derates" that leave truckers and farmers stranded in life-threatening temperatures.
- •Ryan Anderson (Commissioner, Alaska Department of Transportation and Public Facilities) reported that emissions system failures account for 80% of diesel maintenance issues in Alaska's extreme Arctic environment.
- •Sen. Sullivan (R-AK) pressed Anderson on the dangers of the Dalton Highway, where equipment failures in -50 degree weather can leave drivers hundreds of miles from help.
- •Sen. Whitehouse (D-RI) and John Walke (Director, Natural Resources Defense Council) argued the bill is unnecessarily broad, while Republicans contended that current EPA mandates create life-threatening safety risks.
- •This legislation seeks to codify cold-weather exemptions to ensure the reliability of emergency vehicles, school buses, and transport trucks operating in regions where temperatures regularly drop below zero.
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Hearing Analysis
Overview
The Senate Environment and Public Works Committee met on March 11, 2026, to examine S.3135, the Cold Weather Diesel Reliability Act. Chaired by Sen. Shelley Moore Capito (R-WV), the hearing focused on the unintended safety and operational consequences of Environmental Protection Agency (EPA) regulations regarding diesel engine emissions. Specifically, the committee discussed "derates"—a software-mandated reduction in engine speed to five miles per hour—that occurs when Selective Catalytic Reduction (SCR) systems or Diesel Exhaust Fluid (DEF) sensors detect a malfunction. While intended to ensure compliance with nitrogen oxide (NOx) emission standards, witnesses argued these systems frequently fail in extreme cold, stranding drivers in life-threatening conditions.
The hearing was prompted by reports from Alaska, Wyoming, and other cold-weather states where DEF, which freezes at 12 degrees Fahrenheit, causes system failures despite onboard heaters. Sen. Dan Sullivan (R-AK), a primary sponsor of S.3135, emphasized that in remote areas like Alaska’s Dalton Highway, an engine derate is not merely an inconvenience but a "matter of life and death" due to sub-zero temperatures and a lack of emergency services.
Key Testimony
Ryan Anderson, Commissioner of the Alaska Department of Transportation and Public Facilities (DOT&PF), provided technical testimony on the impact to state infrastructure. He reported that 70% to 80% of his department's diesel engine maintenance issues over the past two years were related to emissions control systems. Anderson noted that 10% to 30% of Alaska’s heavy equipment fleet is often unavailable due to these faults, leading to runway closures in rural communities and delayed emergency responses. He cited a specific instance where a maintenance unit failure cost $45,000 in repairs and sidelined the equipment for a year.
Todd Fornstrom, President of the Wyoming Farm Bureau Federation, testified on behalf of the American Farm Bureau Federation. He highlighted the economic burden on the agricultural sector, noting that DEF requirements have decreased fuel efficiency from approximately 6.5 miles per gallon to 4 miles per gallon. Fornstrom described the "limp mode" as a critical threat during harvest and planting seasons, and a safety hazard for ranchers feeding livestock in ground blizzards. He advocated for the total elimination of DEF requirements for agricultural equipment but supported S.3135 as a necessary common-sense step.
John Walke, Director for Clean Air Programs at the Natural Resources Defense Council (NRDC), offered the sole testimony in opposition to the bill. Walke argued that S.3135 is unnecessary because the EPA has already directed manufacturers to update software to allow vehicles to travel up to 8,400 miles before a derate occurs. He expressed concern that the bill’s language provides overly broad exemptions that could apply nationwide, not just in cold weather. Walke and Ranking Member Sen. Sheldon Whitehouse (D-RI) used the hearing to criticize the broader deregulatory agenda of the Trump administration and EPA Administrator Lee Zeldin, citing rollbacks of soot, mercury, and greenhouse gas standards.
Policy Proposals
S.3135 proposes to authorize diesel engine manufacturers to provide a temporary override of the automatic derate or shutdown functions in targeted cold-weather environments or where such restrictions are "impractical." The bill aims to codify flexibility that the current EPA has begun to offer through administrative guidance.
Overview
The hearing revealed a sharp partisan divide. Republicans focused on the "one-size-fits-all" nature of federal mandates and the immediate safety risks to truckers and farmers. Sen. Cynthia M. Lummis (R-WY) highlighted the case of a Wyoming mechanic, Troy Lake, who was imprisoned for bypassing DEF systems to keep engines running in the cold before being pardoned by President Trump. Conversely, Democrats emphasized the public health risks of NOx pollution, which causes respiratory illness and smog. Sen. Alex Padilla (D-CA) argued that if cold-weather states receive exemptions to weaken standards, California should similarly be granted the flexibility to implement stricter standards to protect its non-attainment areas.
Key Testimony
Notable exchanges included Sen. Sullivan’s pointed questioning of Mr. Walke regarding the NRDC’s characterization of these issues as "perceived" rather than "real" concerns. Sullivan also introduced testimony from the Interior Alaska Fire Chiefs Association and the Anchorage Fire Department, noting that even emergency vehicles in Alaska’s largest city face reliability issues due to DEF failures.
The committee did not announce a specific date for a markup of S.3135. Chair Capito set a deadline of March 25, 2026, for written questions for the record, with witness responses due by April 8, 2026. The legislation remains a priority for the Republican coalition representing rural and Arctic regions.
Transcript
Well, good morning and thank you all for being here. Appreciate it. Today we will be receiving testimony on S. 3135, the Cold Weather Diesel Reliability Act, sponsored by Senators Sullivan, Lummis, Curtis, and Murkowski. This legislation is meant to address the serious safety issue for drivers of diesel trucks and equipment in certain parts of our country. And I know two of our witnesses have traveled very far to today and appreciate you all being here. Since 2010, to comply with EPA vehicle emission regulations for NOx, most new diesel engines have used a technology known as selective catalytic reduction, or SCR. SCR is an emissions control system that sprays diesel exhaust fluid, or DEF, into the vehicle's exhaust stream to reduce NOx emissions. To maintain the proper function of the emissions control system, drivers must continuously fill the vehicle with DEF. To ensure compliance with emission standards, the EPA requires manufacturers to install on-board diagnostic sensors that detect when NOx emissions are too high, signaling that the vehicle is out of DEF. When the sensor detects an issue, it triggers the engine controls and software to severely limit an engine's performance through what is called a derate. That's about as technical as I'm going to get with you. When the vehicle derates, it cannot go faster than five miles per hour. However, vehicle derates are not limited to instances when the vehicle is out of DEF, but occurs at any time when the emissions control technology is not functioning correctly. Emissions sensor failures can cause these restrictions as well as prolonged cold weather, which can freeze DEF and prevent it from entering the exhaust system. No matter the reason, if the sensor detects an emissions system malfunction, a driver has just four hours to fix the problem before the five mile per hour restriction kicks in. This system response in rural and cold weather regions can and has resulted in farmers' tractors shutting down in the middle of a field during harvest season or stranded truckers in sub-zero temperatures on isolated roads in northern parts of the country. In 2021, sensor failures led to thousands of trucks across the country being derated and thus out of service for an immediate solution. To address this issue in emergency vehicles, such as fire trucks and ambulances, in 2012, the EPA exempted emergency vehicles from this requirement when responding to an emergency. The Cold Weather Diesel Reliability Act takes a similar approach by authorizing manufacturers to override the system in targeted or cold weather environments. By exempting diesel engine derates in Alaska and other parts of rural America where so many folks rely on diesel trucks and equipment for their livelihood and transportation needs, the bill seeks to address this critical safety issue. I want to thank my colleagues for championing safety in transportation and working to address the unique needs of Alaska, Wyoming, and other cold weather states. I'd also like to thank the Trump administration for recognizing the importance of protecting our America's farmers and truckers. Last year, EPA Administrator Zeldin issued guidance to allow more flexibility and longer warning times before derates occur and is gathering information to help fix this safety problem. So I look forward to this topic and I'll now recognize Senator Whitehouse for his opening statement.
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