Serving as a bright and bold last-chance warning for vehicles about to enter tunnels, this wall of water painted turns into a kind of hovering hologram designed to STOP impending drivers from creating or compounding tunnel disaster situations.

Dubbed Softstop and deployed first in Australia, the liquid signage does no damage should a car or truck pass through, but still provides an impossible-to-ignore signal for drivers. It is used to warn off too-tall trucks and deter Sydney Harbor Tunnel entry in cases of fires or crashes going on inside the tunnel.

This solution came about after conventional signage failed to warn off drivers in an emergency. “We had a fire in the tunnel,” explains Harbor Tunnel GM Bob Allen, “motorists ignored the warning lights and signs and continued driving towards the fire. These drivers exposed themselves to smoke and toxic fumes from the fire and then to compound the situation they turned around (in a one way tunnel) and drove back out of the tunnel against incoming traffic.”

The wall-of-water solution came about as a collaboration between Laservision, a creative technology firm that designs architectural lighting, and a pump manufacturer: Grundfos.