Congress gave California permission to regulate emissions from in-use nonroad mobile sources of pollution. This primarily applies to engines that run transportation refrigeration units (TRUs), such as the refrigeration units on trucks carrying perishable goods. Other states may follow a rule identical to the one adopted in California or adopt no rule at all. EPA must approve a proposed California regulation unless EPA finds the standard unjustified given air conditions in California or because the cost of compliance is too high. The California Air Resources Board devised a plan in 2004 to reduce particulate matter emissions from diesel TRU engines by 75% by 2010 and 85% by 2020. The rule began to phase in 2009; it applies to trucks based in California and trucks operating in California—such as a truck from another state that picks up a load of fruit in California.

1. Is it likely that most trucks with refrigeration units will, in fact, comply with the California standard, thereby making it nearly a national standard?
2. Is a cost of $2,000 to $5,000 per truck not significant?