Cutting-edge technology to prevent trucks from getting stuck in Sydney tunnels will be trialled in a bid to reduce traffic bank-ups on major roads.

The NSW government says the six-month trial will combine  WiFi Flood Sensor technology and warning signs to divert trucks taller than four metres from entering tunnels and getting jammed.

Trucks will be scanned by the sensors, and their height and number plate will be displayed to drivers on overhead digital signs further along the road.

The trial is part of a crackdown on trucks jamming tunnel entrances and causing major disruptions to the city's road network.

Roads Minister John Graham said the government was "resolute in its commitment to stopping overheight trucks from shutting down our city and inconveniencing motorists".

"This new technology on trial will help us strengthen the approach even further," Mr Graham said in a statement on Friday.

Transport for NSW executive Craig Moran said the move would save time and money for motorists and save money for the state by reducing "closure minutes" for tunnels.

The first trial is under way on the southbound lanes of the M1 Pacific Motorway at the Mount White Heavy Vehicle Safety Station, the government said.

"We're starting at Mount White but aim to eventually roll out this new technology to all key heavy vehicle routes entering Sydney. We'll evaluate the results of the trial in six months' time," Mr Moran said.