You cannot drive your car in 1 meter spaced convoys. In many cities jamming the navigators would cause the cars to not fit on the roads, resulting in gridlock for however long the jammers could be kept going.
And dumping 500 caltrops off an overpass would likely have the exact same effect. Worrying about someone actively attacking this kind of system using theoretical jammers that could seize up multiple lanes of traffic (without easy line of sight!) and operate for hundreds of feet at this point seems premature.
You can't do the caltrop trick at 50 locations for weeks on end.
The thing about lasers is they use a very narrow slice of wavelengths. Environmental light like sunlight has very little power within that slice, so its easy for the LIDAR to see its own laser. But that makes it really easy to jam. You could probably build a jammer today for a few hundred dollars, which means that in the future every disaffected monkeywrencher will do it. Ergo the approach is not suitable for the mass market.
