The Easter break has been tragically marked by several road deaths involving motorcyclists around the country.

In the latest incident, emergency services were called to South West Rocks on the NSW mid north coast on Sunday afternoon.

They found a rider had crashed on the road before becoming trapped under a nearby vehicle.

Emergency crews worked to free him before he was treated by paramedics for critical injuries, however, he died at the scene.

Earlier, in far-north Queensland, a 31-year-old man lost control of his quad bike on a local road at East Palmerston near Innisfail on Saturday.

His green Kawasaki struck a pole and he was pronounced dead at the scene.

Nearly two hours later, a black Honda motorbike collided with a Kia Cerato in Thornlands, about 30km southeast of the Brisbane city centre.

The 18-year-old rider died after being transported to hospital with critical injuries. The Kia driver was uninjured.

In South Australia, two men, one riding a Honda motorcycle and the other a Suzuki, died in a collision at Paracombe in the Adelaide Hills about 2.30pm on Saturday.

Another SA man, riding a Harley Davidson, died on Friday after police said he crashed into a traffic light.

While in NSW, a man in his 40s, travelling with several other motorbike riders, crashed on the Monaro Highway near Cooma on Friday and died at the scene.

In other road deaths, a mother-of-four from interstate was killed after a crash in Queensland.

The 51-year-old Victorian was a passenger in a Ford hatchback travelling on School Road in Logan Reserve, south of Brisbane, about 9pm on Saturday when her car was hit head-on by a Ford Falcon utility.

The victim, who had been returning from a family celebration, died at the scene.

Her 21-year-old niece sustained serious leg and back injuries, while a one-year-old child in the car miraculously escaped harm.