Via our sister site Better Roads and the always entertaining Jalopnik, when faced with the rampant problem of semi trucks entering tunnels and overpasses with too short a clearance, the city government in Sydney, Australia has turned to an extremely clever implementation of the stop sign that simply can’t be ignored.
As you can see in the image above, when a semi triggers a sensor along the roadway that indicates it is nearing the tunnel, a curtain of water is released from the top of the tunnel and a projector inside projects a huge, bright stop sign across it.
The stop sign system is made by a company called Laservison and Sydney has been using the projected signs since 2007. Unfortunately, despite the clever trick and the success of actually getting the trucks to stop, the semis have still reached a point of no return since the entrance of these tunnels is essentially a corridor packed with cars they can’t simply turn around out of. That means traffic backups that last for hours until the road is cleared.
You can watch a video of the signs in action below.