Diesel Vehicle Emissions Control Program

Program Rationale​

Controlling particulate matter, the primary ingredient in thick, black diesel exhaust smoke, remains an important health concern. Due to the small size of particulate matter, it is easily inhaled into the lungs where it may damage tissue and can exacerbate conditions such as asthma and emphysema.

Since 1984 most Marylanders have had their cars tested regularly for excessive emissions where diesel trucks and buses operating in and driving through Maryland have not had to be tested. It is only fair that everyone be involved in improving Maryland's air quality.

How the Program Works

MDE provides technical support and coordination to the multi-agency, state-wide Diesel Vehicle Emissions Control Program. The Program affects any diesel-powered vehicle with a gross combination or gross vehicle weight rating of over 10,000 pounds traveling on Maryland's highways. Enforcement is carried out by the Maryland State Police and the Maryland Transportation Authority Police (MTAP), who can require any heavy-duty diesel vehicle to submit to a smoke emissions test at any time or place.

Failing the Diesel Emissions Test

The owner of a Maryland-registered vehicle that fails a smoke test will be issued a Safety Equipment Repair Order (SERO). Owners must have that vehicle repaired and retested within 30 days of receiving a SERO or face having that vehicle's registration suspended.

Certified Diesel Emissions Retester

A Certified Diesel Emissions Retester (CDER) is someone who is certified by the State to conduct retests and certify that the vehicle has been brought into compliance with the applicable smoke opacity standards. CDERs include certain Maryland State Police inspectors and diesel vehicle repair technicians located throughout the State.

Useful Web Links

Included are links to the Maryland State Police, Maryland's toll facilities, local and regional trucking organizations, and other sources of information.

Maryland's Diesel Emissions Vehicle Control Program Brochure

State Diesel Emissions Testing Programs​

Smoking Vehicle Hotline
Report a Smoking Vehicle On-Line​​