32-year-old David Steyn fell about 10m off the Roger Dyason Road bridge.
He broke his nose, left cheekbone, left knee and thighbone. He also has cuts on his face from the incident during which he had to be transported by helicopter to Milpark Hospital in Parktown, Johannesburg.
He is currently in a critical condition.
According to Steyn's twin brother, Herman, he had told him to catch a taxi on the other side of the bridge.
Herman told Channel24 that there were no lights or railings where Steyn fell off and you couldn't see that it was a bridge.
"The road was very dark. I have many witnesses that have contacted me in the meantime, and someone also told me that they were there the previous evening and almost did the same as they didn’t realise they were walking over a bridge. It was very dark and a freak accident that could’ve been prevented as there were no railings on the bridge."
David had tried to cross the road and fell into the concrete canal on the shoulder of the road under the bridge.
Herman said his brother was completely conscious after the fall. He insisted his brother was sober at the time.
"I think David only had one beer that afternoon and then we decided not to buy beer there because the queues were too long. We stuck with soft drinks the rest of the evening."
David will undergo surgery on Friday to insert plates and screws into his left leg. "If everything goes well they will start to wake him up on Saturday or Sunday. He will obviously still have to stay in ICU for a few days, but he is stable, and we are very lucky that he didn’t sustain any internal injuries or brain injuries and he didn’t break a neck or a back, which is amazing," said Herman.