Truck NOx Rule Flexibility Spurs Fears Amid Unclear Litigation Outlook

EPA’s publication of its strengthened heavy truck emissions standards is raising questions about whether states or environmental groups might challenge parts of the rule in court or urge the agency to reconsider them, after officials included an industry-friendly provision easing requirements during certain low temperature periods. The compliance flexibility could allow per-vehicle nitrogen oxide (NOx) emissions in some conditions about 60 percent higher than California’s truck rules, critics fear, sparking concern that EPA’s standards could allow an improperly high contribution...