More than one in three drivers in NSW have nodded off behind the wheel for a “microsleep” that can last as little as one second but still have deadly consequences, a new study has revealed.

The shocking findings come as tiredness continues to be the second-highest killer on state roads with 74 fatal fatigue-related crashes last year compared with 55 blamed on alcohol and 167 related to speeding.

The survey has prompted police and road safety experts to warn drivers about the dangers of tiredness in the lead up to the Christmas holidays.

Authorities classify nodding off behind the wheel for between one and 10 seconds as a “microsleep”, and say that even the shortest period can be fatal even in urban areas. If a car is travelling at 100km/h, a 10-second microsleep means the driver is out of control of the vehicle for up to 270 metres.

A survey by insurance company Budget Direct found that 39.6 per cent of drivers in the state admitted they had nodded off while behind the wheel.

Bernard Carlon, executive director of the Centre for Road Safety, said getting behind a wheel after going without sleep for 17 hours was equivalent to driving with a blood-alcohol level of 0.05, the legal limit.

Even sleeping for less than five hours for three nights can seriously impair driving.

He said that by the time you start blinking or having a microsleep “it is inevitable that you need sleep”.

Mr Carlon said the best thing for a tired driver was to pull over, have a coffee and nap for 20 minutes, but no longer, or you feel drowsy.

“The caffeine kicks in at the end of the period and sparks your brain function after sleep,” he said.

“We stopped talking about fatigue a few years ago and started talking about people being tired like shift workers and students because we know that a lot of crashes linked to tiredness happen on short trips.”

The study found that fatigued drivers are most vulnerable on long stretches of road because of the higher speeds as the brain can be lulled into an almost trancelike state that results in “blank stares, head snapping and prolonged eye closure”.

“Driver fatigue can and does occur and, as a result, vehicles do cross to the wrong side of the roadway into the path of oncoming vehicles or hitting objects on the side of the road,” Highway Patrol Assistant Commissioner Julie Middlemiss said.

Budget Direct’s Jonathan Kerr said drivers were four times as likely to have a fatigue-induced fatal crash between 10pm and dawn.

“While it can be hard to establish just how many of these deaths are the result of microsleeps, fatigued driving killed more people in NSW from 2013-2017 than drink driving,” he said.