Cameras capture the moment the unnamed daredevil was flung from the kids' toy as the flimsy vehicle spiralled out of control as it hurtled along at breakneck speeds towards oncoming traffic.
The clip, uploaded to YouTube, shows the rider, sporting a crash helmet and knee pads, come a cropper on Slack Hill in the Derbyshire Dales near Sheffield - as friends filming from a vehicle in front collapse into laughter as the go kart smashes into a grass verge and falls apart.
The child's pedal kart is shown gradually picking up speed as cars pass in the opposite direction with footage showing it wobbling and rattling as it gathers pace.
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The driver is eventually thrown off the kart when crossing a double white line in the carriageway appears to cause it to lose control, with the black plastic seat flying off onto the road in the smash.
As the driver comes to a sticky end, friends filming the crazy scenes from a pick-up truck in front can be heard laughing, before racing back to see if their pal is OK.
One shouts: "You alright?," to which the shaken rider replies "yeah" before adding: "F***, that got scary. I was shaking."
His friend replies: "That was so f***ing fast.
Another voice adds: "Good effort, that was incredible. 45mph an hour you were going there."
The 2 minute 40 second clip, entitled Insane Go Karting - Steep Hill was uploaded last week by a user called Steel City Media with the description "45mph on a Go Kart down Slack Hill just outside of Sheffield."