Exhaust emission testing is generally only considered necessary by Local Authorities where air quality is marginal or exceeds the Air Quality Objectives. 

In Merthyr Tydfil the air quality is currently within acceptable limits and as a result it has not been necessary to delare an Air Quality Management Area (AQMA).  If it becomes necessary to declare an AQMA at some point in the future then vehicle exhaust emission testing may be considered with the cooperation of the Police and VOSA.