Charlie Bristow was travelling along the M5 towards Staffordshire with his dad and cousin on Saturday when he spotted the stowaway reptile.
Video shows the 25-year-old passenger leaning over his dad James Bristow, who is driving, to film the grass snake slithering around the front bonnet and onto the right wing mirror.
As it makes a treacherous move to the side of the car, one of Charlie’s family can be heard anxiously saying: “bloody hell”.
The snake then slithers to the top of the wing mirror while continuously sticking out its tongue – which they are known to do to smell their surroundings and warn off other animals.
After realising it can’t go any further, it then tries to curl back around to get back to the bonnet.
A passenger can be heard saying: “Jesus Christ, I don’t think I have ever seen a snake.”
The unfortunate reptile then falls from the car and tumbles onto the concrete motorway while the men in the van can be heard screaming: “oh no”.
Videographer Charlie posted the video on TikTok yesterday, writing: “Just cruising down the M5 when this happened.
“We tried to pull over but there wasn’t a hard shoulder.”
The video has been viewed over 25,000 times and attracted dozens of comments from shocked viewers.
One said: “Poor little grass snake, I hope he’s good.”
Another wrote: “I’m going to pretend there’s a part 2 and the little guy is ok.”
A third added: “You should have opened the window and let him in.
“He’s just a harmless grass snake.”
Another commented: “Why have I seen this, I’m gonna be checking everything.”
One person added: “I would have crashed.”
Speaking today, Charlie said: “My dad, the driver, spotted it first and shouted ‘Oh my god there is a f***ing snake there’.
“Me and my cousin Max were like ‘what?’
“We didn’t initially see it for a good 10 seconds or so.
“My dad steered into the slow lane and slowed down causing the car behind to beep at us.
“I then got my camera out and started filming.
“We were probably going 70mph when it popped its head out.
“We were in the middle lane but quickly moved into the slow lane.
“We really wanted to pull over and save it, but unfortunately it was a smart motorway so we couldn’t pull over.
“We were parked in a field and it must have crawled up into the engine bay as it liked the warmth.”
Grass snakes are mainly found in lowland areas of Britain.
They are particularly populated in some areas of the south and south east of England.
The harmless snakes are protected under the Wildlife and Countryside Act making it illegal to knowingly injure or kill them.