That’s a nice idea but it would require a lot of elements to work in perfect synchrony to be really safe and reliable. In the foreseeable future, probably easie

That’s a nice idea but it would require a lot of elements to work in perfect synchrony to be really safe and reliable. In the foreseeable future, probably easier just to put physical bollards in. Your comment reminds me of a funny aside in Arthur C Clarke’s The Fountains of Paradise (wonderful novel, about the construction of a space elevator). A famous architect, designing the world’s longest and highest bridge, fights to avoid putting guard rails along the sides. His justification is a) cars are all computer-controlled and totally reliable in the book’s setting, so rails are unnecessary; some suspect it’s actually b) the bridge will look nicer without guard rails; or even darker, c) if a car does somehow go off-course, he’d prefer it doesn’t damage the bridge before plummeting half a mile into the sea.