The Port of Los Angeles is the largest and busiest port in the United States.  Ships, trains and trucks form an amalgamation of freight movers and with it comes concentrated amounts of harmful emissions creating what has been “dubbed the ‘Diesel Death Zone’ because it’s one of the largest sources of air pollution in Southern California.”
Figure: Aerial View of the Ports of Los Angeles and Long Beach
To slow the rising levels of deadly nitrogen oxides and cancerous particulate matter the California Air Resource Board (CARB) created the Clean Truck Program (CTP) in October 2008. The CTP immediately banned all pre-1989 trucks from entering the port. At the same time, CTP made “$44 million in payments to licensed motor carriers in order to incentivize their purchase of 2,200 Clean Trucks.” The trucks that replaced the aging fleet generated emissions nearly 90 percent lower than the previous generation. The port continued slashing emissions by banning all 1989-1993 trucks in 2010 and then in again 2012 prohibiting all trucks that did not meet the 2007 Federal Clean Truck Emissions Standards. 
The aggressive push to phase out old, dirty trucks falls in line with the program objectives. To achieve positive, long-term growth for the program, the CTP encourages investment in cleaner, greener trucks, alternative fuels and emerging technologies . Another objective is mitigating the effects the port has on the local community. After local regulators discovered elevated levels of air pollution around the area surrounding the port, mainly low-income and minority neighborhoods, the port took accountability for the health impacts of the freight movement.
Since 2007, the Clean Trucks Program has spurred over $1 billion dollars in investments to put 9,800 clean trucks in operation at the Port of Los Angeles.  The new trucks, combined with the removal of dirty trucks, have reduced emission levels at the port by 80% since the program’s start in 2008. The emissions reduction from the Clean Trucks Program is equivalent to removing 300,000 automobiles from Los Angeles every year. 
The long-term outlook of the Clean Truck Program is also promising. Los Angeles is expected save about $10 billion dollars on health cost between now and 2025 as a result of cleaner skies. CARB formulas estimate that with the CTP, Southern Californians will “pay between $100 million and $590 million annually in health impact cost related to [port related] drayage truck pollution.” 
Although the benefits of the Clean Truck Program are widely praised by public health advocates, not all are satisfied with the aggressive policies of the program. The Supreme Court is currently hearing arguments from trucking associations at the port who claim the Clean Truck Program violates a 1994 federal law that deregulated their industry. The federal law called into question is the 1994 Federal Aviation Administration Authorization Act, or FAAAA, which the trucking associations say pre-empts the port's program. 
The Supreme Court justices “seemed receptive”  to the trucking associations’ plea, and other transportation hubs are closely watching the results of this legal battle which may have implications for ports across the United States. If struck down, the Clean Trucks Program will likely be dissolved, and will put the Port of Los Angeles back at risk to return to pre-2007 pollution levels.