I did a bit of research on this while having a go at the Dunedin City Council for their roading efforts…but that’s another story. The Californians have been aware of this sort of driver behaviour for a while. Basically if the road appears wider the drivers will feel more confident and drive faster. Bikers don’t suffer from it as much because on a bike the lane always appears so wide. (Unless doing 220km/h). Anyway in LA rather than put in curb protrusions and change double lane roads in to single lanes to try to slow people down, they plant trees along both sides of the road. This makes drivers feel like they are going through a tunnel and they slow down.