sort of repeating others but ..
Alluding to fog comments, any EM wave real world use experts know what's the absorption of that short wavelength EM like by water droplets.
Obviously its a noticeably shorter wavelength than a microwave oven (which is particularly good at being absorbed by water hence its cooking ability), it's only approx factor 10 difference, so would be interested to know if it is likely to be adversely affected by rain / drizzle / fog etc. (basically take your pick of lots of common UK weather)
If absorption is quite high then you need car to have decent output power to compensate (otherwise a fairly limited range)