AICold-Weather Diesel Emissions Rule Safety Concerns and Proposed Fix

Environmental Permitting and Water InfrastructureSenate Environment and Public Works · 2026-03-11 · 119th Congress
The Senate Environment and Public Works Committee held this hearing to examine S.3135, the Cold-Weather Diesel Reliability Act, which would let EPA authorize manufacturers to suspend automatic engine derate or shutdown functions triggered by diesel exhaust fluid (DEF) system malfunctions in extreme cold. Begins at 0:18:25
Transcript
Highlights

Title

Cold-Weather Diesel Emissions Rule Safety Concerns and Proposed Fix

Purpose

The Senate Environment and Public Works Committee held this hearing to examine S.3135, the Cold-Weather Diesel Reliability Act, which would let EPA authorize manufacturers to suspend automatic engine derate or shutdown functions triggered by diesel exhaust fluid (DEF) system malfunctions in extreme cold. Witnesses from Alaska's Department of Transportation, the Wyoming Farm Bureau, and the Natural Resources Defense Council testified on safety incidents, equipment costs, and concerns about the bill's scope, while members debated it alongside broader disputes over EPA deregulation under the Trump administration. Begins at0:18:25

Who spoke

Chair Shelley Moore Capito (R-WV)0:18:25: Explained that SCR/DEF emissions systems can trigger a five-mile-per-hour "derate" when sensors detect malfunctions, sometimes from cold-frozen DEF0:19:410:20:07; noted 2021 saw thousands of trucks derated nationwide and that EPA exempted emergency vehicles from the requirement in 20120:20:39; later questioned Anderson on public-safety differences between D.C. and Alaska derates0:59:43 and Fornstrom on planting/harvest impacts1:03:57.

Sen. Sheldon Whitehouse (D-RI), Ranking Member0:21:38: Argued EPA under Administrator Zeldin has rescinded greenhouse gas tailpipe standards (estimated $580 billion–$1.4 trillion cost to consumers)0:25:14 and the endangerment finding0:25:42, cut enforcement actions 75-81% versus prior administrations0:27:00, and warned of a "climate insurance collapse" threatening mortgage and real estate markets1:06:26; questioned Walke on the $820 billion annual health cost of fossil fuel pollution1:08:21.

Sen. Dan Sullivan (R-AK)0:29:34: Sponsor of S.3135; described a Dalton Highway trucker stranded at -45°F when DEF crystallized, requiring hours of idling and a $15,000 tow0:32:55; introduced witness Ryan Anderson0:36:23; later pressed Anderson on the 70-80% DEF-related maintenance rate and 10% fleet unavailability1:24:541:25:44, and challenged Walke's characterization of concerns as "perceived"1:34:13.

Ryan Anderson, Alaska DOT Commissioner0:38:16: Testified emissions control systems are now the largest source of diesel maintenance failures, causing 70-80% of issues over two years and leaving 10-30% of the fleet unavailable on a given day0:41:08; cited a $45,000 repair case with a year-long equipment outage0:41:23 and described the Dalton Highway's single gas station over 350 miles1:23:32.

Sen. Cynthia Lummis (R-WY)0:43:42: Introduced witness Todd Fornstrom; described a Wyoming constituent imprisoned for illegally altering a diesel engine's emissions system to keep it running in cold weather, later pardoned by the President0:45:07; argued DEF requirements paradoxically lower fuel efficiency and increase emissions1:15:24; asked Anderson whether derates occur even with sufficient DEF present1:12:56.

Todd Fornstrom, Wyoming Farm Bureau Federation President0:48:42: Said DEF requirements have added significant costs and reliability problems for farm equipment, describing tank freezing/cracking and reduced fuel efficiency (from ~6-6.5 to ~4 miles per gallon)1:15:04; described trucks regularly disabled by derates alongside I-80 as a safety hazard1:31:34.

John Walke, National Resources Defense Council0:54:13: Opposed the bill, arguing EPA has already directed manufacturers to extend run-time before derate and is collecting data from 14 manufacturers0:54:39; warned the bill's exemption applies nationwide, not just to cold weather, due to its wording1:21:09; withdrew "perceived concerns" language on cross-examination while affirming the regulatory process, not statute, should resolve the issue1:35:181:36:26.

Sen. Alex Padilla (D-CA)1:16:25: Argued that if cold-weather states deserve regulatory flexibility, California should retain its own Clean Air Act waiver authority, which Congress voted to rescind1:16:57; asked Walke about public health consequences for California's nonattainment areas1:17:58 and whether broad exemptions undermine regulatory consistency1:20:50.

Sen. Pete Ricketts (R-NE)1:27:46: Said Nebraska producers report DEF-related issues account for a majority of machinery repairs and can trigger limp mode during critical planting/harvest windows1:28:08; asked Fornstrom and Anderson about safety and operational benefits of the bill1:30:49.

Key moments

Sullivan described a Dalton Highway trucker whose truck lost power near Atigun Pass at -45°F with wind chills near -70 to -80°F, was stranded for hours with no cell service, and whose company paid $15,000 to tow the load back0:33:200:34:12.

Anderson testified that 70-80% of Alaska DOT's diesel maintenance issues over the past two years stem from emissions control systems, with 10-30% of the fleet unavailable on any given day, and cited a case costing $45,000 in added costs with equipment out of service for a year0:41:080:41:23.

Lummis said a Wyoming constituent was imprisoned (later pardoned by the President) for illegally modifying an emissions system to keep diesel engines running in cold weather, calling the outcome absurd compared to leniency shown to violent criminals elsewhere0:44:090:45:07.

Fornstrom said fuel efficiency dropped roughly 50% (from 6-6.5 mpg to about 4 mpg) after DEF systems were added, and that DEF tanks can crack when the fluid freezes and expands, stranding equipment1:14:341:32:37.

Walke disclosed that the bill's exemption is not limited to Alaska or to cold weather — because of how it is worded, it could apply to ambient air temperature nationwide regardless of season1:21:09.

Padilla drew a parallel between the bill's cold-weather flexibility rationale and California's rescinded Clean Air Act waiver authority, asking Walke about health consequences for the state's nonattainment areas, home to a plurality of Americans living in such areas1:16:571:19:43.

Sullivan pressed Walke on calling Alaskans' concerns "perceived," and Walke withdrew the word, affirming the concerns are "absolutely real"1:35:131:35:18.

Whitehouse cited NRDC's finding of $820 billion per year in health costs from fossil fuel pollution, including about 107,000 premature deaths annually, and compared it to an IMF estimate of $770 billion in fossil fuel subsidies1:08:501:10:04.

Anderson said the Dalton Highway had closed the night before the hearing for over 24 hours due to a storm, illustrating the isolation and equipment-response challenges unique to Alaska1:00:08.

Fornstrom said DEF-related derates regularly strand trucks along a 70-mile stretch of I-80 near the Wyoming-Nebraska border, where drivers cannot get safely off the roadway1:31:341:31:55.

Metadata

Official titleHearings to examine S.3135, to require the Administrator of the Environmental Protection Agency to authorize manufacturers of certain vehicles to suspend engine derate or shutdown functions in prolonged cold weather conditions.
CommitteeSenate Environment and Public Works
Chamber / CongressSenate · 119th Congress
Date2026-03-11
TypeMeeting
Witnesses
(none listed in event metadata)
Videosenate-isvp
Transcript241 caption blocks · 10,916 words · 1:39:52 runtime
EventCongress.gov 338045