The Sydney trucking company involved in a crash that killed three people in 2012 has been fined more than $1.2 million for speeding offences.

Last month, Zaens trading as Lennons Transport Services pleaded guilty to 172 offences, and company director Tony Lennon pleaded guilty to 20.

The company's trucks repeatedly exceeded the speed limit by 15kph between February 2011 and March 2012.

A court heard that the company recorded three speeding offences since one of its trucks careered onto the wrong side of the Hume Highway and hit a car, killing three people, in January 2012.

Today, the Downing Centre Local Court found that the company's trucks had been repeatedly speeding because of a failure to make sure its drivers were abiding by the limits.

"Zaens did not make management responsible for speeding" apart from during a drivers' induction process, it found.

"Numerous offences occurred because of a failure of Zaens to design a system to ensure compliance with the law".

The court also found there was no evidence that management was required to check average speeds on logs and no evidence of a standard time for a particular route.

In a letter to the court last month, Mr Lennon suggested that his presence at the business was a deterrent to speeding.

The court rejected that, finding he was personally responsible as director of the company and his actions were "close to the worst case".

Mr Lennon was fined more than $80,000.

He walked out of the court as the magistrate read out her decision.

In a separate case, Lennons driver Vincent Samuel George was found guilty of manslaughter earlier this year after a court found he was drug-affected and sleep deprived in the lead-up to the 2012 crash that killed three people at Menangle, south of Sydney.