A truck reportedly slammed into the Montague Street bridge in South Melbourne shortly before 3.30pm on Friday.

The accident comes despite the installation in May of large gantries designed to warn drivers that their trucks are too high to pass.

The bridge has been hit with such regularity, there's a website that counts down the number of days since the last incident. The bridge also has its own satirical Twitter account.

It has been just 10 days since a truck last hit the bridge on October 11, which was the second vehicle to hit the bridge that week.

An eyewitness told radio station Triple M on Friday the truck hit the gantry, which was erected to prevent this exact thing, but the driver failed to stop.

"He hit the first gantry and then kept on going. It hit round 300 millimetres above the bridge's edge," the witness said.

With Daniella Miletic