Graeme Brouder, 36, from Twickenham in south-west London, said: "I was coming off the other side of the bridge towards the tolls at about 16:30 BST on Friday.
"I was about five cars from the barrier and I saw a guy out of the corner of my eye come running along the side of my car, he ran to the barriers.
"He came back towards the cars, he went across into the lane next to me, tried to get in the car next to me, he was shouting something - I had my windows up so I couldn't hear him.
"He was shouting at that car, tried to get in that car, ran past mine, tried my door handle, and then ran down the lane behind me and he was just shouting at everyone.
"He was running around, he was trying to get in everybody's cars."
