Shocking footage showing the moment a father was killed by a motorist who fell asleep at the wheel has been released by his grieving son.

David Wakefield, 71, was killed on July 28 in 2015 after being smashed into by van driver Christopher Trusler on the A420 near Abingdon, Oxfordshire.

Now his son Ash has shared the video on Facebook as a warning to prevent people from driving when they're tired.

The footage shows two cars driving along before David Wakefield's and Christopher Trusler's vans smash into each other

One truck, carrying dozens of cones, lands on its side, after flipping into the air onto the other side of the road in front of another car

Mr Wakefield (left), 71, was killed on July 28 in 2015 after the crash. His son Ash (right) posted the video to raise awareness of driving while tired

Trusler, who was jailed for two years for death by dangerous driving and received a four year driving ban, had been awake for 14 hours after working a night shift and then starting a day shift back-to-back.

He only served 364 days of his sentence.

The footage shows two cars driving along before Mr Wakefield's and Trusler's vans smash into each other.

One truck, carrying dozens of cones, lands on its side after flipping into the air onto the other side of the road in front of another car.

Motorists can then be seen running towards the scene to help save the people involved.

Ash believes that the blame for his father's death not only lies with Trusler - but also the company who employs him for allowing him to drive after working so many hours.

Christopher Trusler, who was jailed for two years for death by dangerous driving and received a four year driving ban, had been awake for 14 hours

Immediately, the other vehicles brake to avoid a pile-up on the busy road near Abingdon, Oxfordshire

Ash believes that the blame for his father's death not only lies with Trusler - but also the company who employs him for allowing him to drive after working so many hours

Motorists can then be seen running towards the scene to help save the people involved

Posting on Facebook last Friday, Ash, from Cheltenham, Gloucestershire, wrote: 'Today 28th July 2017 at 09:05 will be two years since my Dad was killed.

'I've decided to make the dash-cam footage of a vehicle following my Dad's van public. My Dad lost his life because of a 'Traffic Management Operative' – Chris Robert Trusler from Northampton who fell asleep whilst driving.

'This was due to working a night shift and then starting a day shift without adequate rest, his employer at the time 'Centurion Traffic Management' of Leeds (Centurion Site Services Limited) .

'In my opinion are equally responsible for Dad's death as they should NEVER have asked/let their driver, do so many hours made even worse by him driving a motor vehicle.

'Chris Robert Trusler was sentenced to two years imprisonment for 'Death by Dangerous Driving' and received a four year driving ban. Sadly, due to our justice system he has been released after serving only 364 days.

Ash wrote the emotional post on Facebook last Friday. He began the post: 'Today 28th July 2017 at 09:05 will be two years since my Dad was killed'

'Below is the dash cam footage which is Graphic. The van (flatbed) on the right travelling towards you is being driven by Chris Robert Trusler who has fallen asleep.

'My dad is driving a van on the left-hand side and loses his life in this video.

'Please, please share this video to raise awareness of road deaths but especially in this case of driving whilst tired. I can't bring dad back but hopefully we can warn others.

'Driving is not a given right, it's a privilege. Think before you drive, you could be saving lives.

'Always in our hearts and never forgotten. Until we meet again Dad xxx.'

He added the hashtags, '#dontdrivetired #brakecharity #roadsafety #A420 #Oxfordshire #tirednesskills#dontdrivedrowsy' to his post, urging social media users to share the post.