Mandatory Diesel Retrofit Program

The Mandatory Diesel Retrofit Program was active 2007-2017.

While there are federal engine emission standards in place for newer vehicles, heavy-duty diesel engines have a long service life allowing an older technology, higher-emitting engine to pollute for many decades before it is replaced with a newer, cleaner engine.  To address this gap, the Diesel Retrofit Law was passed in 2005 to clean up emissions from certain on-road, diesel-powered motor vehicles and non-road vehicles/equipment through the use of retrofit emission control technology.  The benefits of this law and the subsequent regulations adopted by the DEP are a reduction of the harmful diesel exhaust that NJ citizens are exposed to every day.  The regulations require a variety of vehicles and equipment to install retrofits by established deadlines at State expense.


What vehicles were covered by the Diesel Retrofit Law?

Owners of regulated vehicles and equipment are responsible for complying with the Diesel Retrofit Program rules.  Regulated vehicles are those that are powered by a diesel engine and include:  

  • School buses 
  • Solid Waste Vehicles that are publicly-owned or used to perform solid waste services under a public contract
  • Commercial Buses owned by private and public entities 
  • Publicly-owned on-road vehicles 
  • Publicly-owned off-road vehicles with at least 175 horsepower 


What do I need to do to comply?

An owner of one or more regulated vehicles or equipment must provide to the DEP an inventory of all the diesel-powered vehicles and equipment within his or her fleet.  The inventory must include information about all of the vehicles/equipment, the compliance method the owner plans to use to meet the required emission reductions for the regulated vehicles/equipment, and the type and cost of the retrofit system.   

Upon approval and certification of funding by DEP for retrofits, the owner must have the vehicles retrofitted in accordance with the inventory submittal.  After retrofitting, the owner must send completed compliance forms to DEP.   

For more information, please read the Mandatory Diesel Retrofit Program Final Report. 


NJ School Bus Emissions Study

The DEP has completed the NJ School Bus Emissions Study to determine if tailpipe retrofit devices further reduce levels of diesel fine particles in school bus cabins. The study concluded that tailpipe retrofit devices do not significantly reduce in-cabin particulate levels. Therefore, the Department will not require tailpipe retrofit devices on regulated school buses. 

DEP also concluded that equipping school buses with closed crankcase ventilation systems, and ensuring that all school buses meet New Jersey Motor Vehicle Commission’s school bus inspection requirements, will substantially reduce the levels of fine particles inside school buses. 

Final Study Report and additional information