The driver of a combined tipper truck and dog trailer was fined for entering the Galston Gorge on October 13, about 9am.
Galston Road has a length restriction of 7.5 metres and the vehicle allegedly exceeded that limit.
The truck was later directed to the Penrith Heavy Vehicle inspection station, where the man, 44, was issued with an infringement notice of $2270 and six demerit points for disobeying signage on the Galston Gorge.
Later, it was also inspected and a number of notices were issued to the owner for a range of defects, including defective brakes and defective seatbelts, which totalled $2592 in fines.
On October 17 the owner was issued a notice and another two of his trucks were brought to Wetherill Park Heavy Vehicle inspection station where officers from the Joint Traffic Task Force inspected them.
One prime mover with trailer was issued a defect notice for having a speed limiter capable of doing 106 km/h. Another prime mover with trailer was issued notices for minor defects.
Assistant Commissioner Michael Corboy of the state's Traffic & Highway Patrol Command said three heavy vehicles entered Galston Gorge last week.
"There are numerous warning signs on the Hornsby Heights and Galston ends of the Gorge, which drivers have been choosing to ignore,” he said.
“There are no excuses for heavy vehicle drivers ignoring signs when surrounding communities are put at risk.
“The companies involved not only run the risk of having registrations suspended, they can also expect to have their fleets inspected and notices issued if their trucks are not up to scratch.”