The NSW Land and Environment Court fined Bowport Allroads Transport Pty Ltd $80,000 and ordered costs of $48,000 for five offences involving its trucks emitting excessive exhaust smoke in the M5 East tunnel between January 17 and March 7, 2007.

The company, which pleaded not guilty, employs 166 workers and uses 60 trucks for its estimated 70,000 movements a year to and from Port Botany.

The judgment said Bowport had five previous convictions and had been issued with 29 fines for smokey vehicles in the past.

In sentencing, Justice Terry Sheahan said the defendant was a ``large and successful enterprise, and it must pay its penalty for past infractions and do better in the future''.

He also ordered Bowport drivers and mechanics to undertake a TAFE course to increase awareness of the impact of diesel emissions and how to reduce emissions. It was the first time a court has made an order of this type.

The offences were detected by the RTA system in the M5 tunnel which records vehicles blowing excessive smoke continuously for more than 10 seconds.

An RTA spokesman said the system was made up of air opacity detectors, vehicle detectors, still and video digital cameras and computer recording equipment, at the beginning and end of the 240-metre length of the tunnel.

A Department of Environment, Climate Change and Water spokeswoman said 148 infringements were issued since 2007 when the tunnel system was first used.

The department has successfully prosecuted 60 smokey vehicle offences in NSW, resulting in $177,000 in fines since 2006.