But about five kilometres further north, as he crossed the Mooney Mooney Bridge and approached the queue of traffic on the M1, Newcastle truck driver Samuel Anthony McLean took his eyes off the road, looking down into the cab of his Mack truck to grab his thermos of coffee.

When he looked back at the road "a second or two" later, he was confronted by a "wall of cars" that were banked up in the northbound lanes.

McLean slammed on the brakes, but his truck collided heavily with a white Ford utility at the back of the queue, riding up onto the tray and causing the Ford to erupt into flames.

Adam Langford, 52, and his nephew, Jack Langford, 19, were trapped in the Ford and killed in the fiery impact.

A couple travelling in the other direction later told police they saw McLean's truck fast approaching the stationary line of traffic.

"Oh my god that fellow is not going to stop," the woman told her husband. "He's not even slowing down."

As a devastated McLean would later tell police, the crash that claimed two lives and injured four others was born out of "a simple lack of concentration".

With the anniversary of the double fatal crash approaching, McLean, 31, of West Wallsend, appeared in Gosford Local Court on Friday and pleaded guilty to two counts of dangerous driving occasioning death and one count of dangerous driving occasioning grievous bodily harm.

He will next appear in Gosford District Court on August 15 to get a sentence date.

During an interview after his arrest, McLean admitted he had seen the electronic warning that signalled queues of traffic up ahead.

But as he approached the Mooney Mooney Bridge he said he became thirsty and reached down to grab his thermos of coffee.

He took his eyes off the road and didn't notice the queues of stationary traffic.

McLean told police at the scene that he looked up and saw the car and "didn't even know if he braked".

"I don't know how I'm going to deal with this," McLean said. "I'm responsible for someone's death."

A crash investigator who examined the scene found that the queues of traffic would have been visible for about 800 metres on the southbound approach to the bridge.

"The time taken for the accused to arrive at the collision site after first being able to observe the slowing and stationary traffic would be at least 28 seconds if travelling at 100km/h and at least 30 seconds if travelling at 95km/h," the crash investigator found.

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