Check out this video about pop-up stop signs made by light show company Laservision are part of an experiment that’s been taking place in Australia since 2007, successfully preventing semi trucks from suddenly turning into unintended convertibles.
From the Mashable article: “Imagine you’re a truck driver. You’re coming up to a tunnel that might be too low for your truck to fit under, but you’re not sure. Suddenly, a gigantic red stop sign appears to obstruct the road in front of the tunnel entrance, giving you no doubt. Stop!”