QUOTE: A pigeon was the cause of traffic disruptions in the Sydney Harbour Tunnel on Wednesday afternoon, after the bird tripped the overheight sensors, causing authorities to shut down the southbound lanes.

The pigeon flying over the top of a semi-trailer passing under the sensors caused the vehicle to register as overheight, with authorities shutting down the tunnel for 20 minutes at 4.30pm.

Road authorities stopped the truck ahead of the tunnel entrance and forced it to reverse back into the slip lane, causing the tunnel to be closed.

The truck was finally allowed to leave an hour later after police had cleared it.

The truck measured a height of only 3.9m, well under the tunnel height clearance of 4.4m, confusing traffic authorities as to how the sensors went off.

Tunnel operators later went back through tunnel CCTV and found a pigeon flying over the truck at the exact moment it passed under the detector, causing it to register as overheight.

It must have been a big pigeon - there's supposed to be two sets of sensors a metre apart in order to ensure such a scenario doesn't occur, although as the Tunnel was built 30 years ago it may be the sensors for it may pre-date that thinking.

Still, a false positive is better than an unfalse one, knowing what happens every time a truck crashes into the M5 portals every time a driver ignores the flashing warning lights.

Some pigeon!
I saw the tunnel video on the news and the bugger is HUGE.
The bird seems to be banking with every wing and feather spread wide.
Probably has stalled and put the flaps out to get some air speed.
Pretty poor sensor with no fail safe secondary.
Fred.

If it was too big to be a pigeon, Perhaps it was a stool pigeon.

Photo uploaded to Post 3.

To me that does not look like a Pidgeon.

It looks more like a B-52.

Maybe a black cockatoo or a hawk - too indistinct to tell. Plenty of Domain and Royal Botanical Gardens parkland thereabouts that they could be living in.

Wing shape & beak suggest a raptor: Now to find a blackish / Dark brown one. So, Hawk, Eagle, Falcon (not Ford) ....

I just had a look at the pictures online and it is indeed a common garden variety pigeon. The bird is flying to the side of the truck, not above it as it might seem . That is why the pigeon appears to be bigger than it actually is.

Fascinating: A Bird with tunnel vision.