A sharp drop in the number of trucks being inspected at the heavy vehicle checking stations has outraged the State Opposition, which says holiday motorists have been at risk from dangerous juggernauts and visual inspections are vital for detecting defects.

Figures from the Roads and Traffic Authority show 82,173 fewer trucks were scrutinised at the checking stations last year than those facing scrutiny the year before, even though an internal RTA report had noted more than a quarter of the trucks involved in road crashes had "serious or dangerous" faults.

Opposition Leader Barry O'Farrell said the figures showed the Government did not understand the risk motorists faced on the state's roads.

"With 80 per cent of Australia's total long distance road freight using NSW roads, this reduction in checks puts motorists in danger," he said.

"These stations are meant to enforce the state's tough truck safety laws.

"The figures show those laws aren't being enforced.

"Heavy trucks are involved in around one in five fatal crashes and cutting the number of inspections can only result in that figure increasing."

Roads Minister Michael Daley said new technology means the truck safety enforcement regime is no longer dependent on "the number of trucks inspected" at the checking stations.

"Instead, an automated computer assessment of a vehicle's or driver's history is carried out at these stations to select high risk vehicles for more detailed inspections," he said.

"In fact, over the past financial year the RTA screened 2.8 million heavy vehicles - which is an increase of 500,000 from the previous year's figures.

"It's important to remember that heavy vehicle inspections at the checking stations are just one component of the State Government's enforcement regime.

"Other features include 100 high-tech enforcement cars that conduct random roadside checks, 27 Safe-T-Cams on known heavy vehicle routes and 280 inspectors.

"The Safe-T-Cam operates 24 hours a day, seven days a week to detect speeding and fatigue infringements, while RTA inspectors can perform random inspections of heavy vehicles on any road at any time.

"These checks are saving lives.

The number of people killed in heavy vehicle fatal crashes dropped, from 95 in 2007 to 75 in 2008."