While most of my driving is in open desert, the past few weeks I've been hanging out (at home) in the Santa Cruz Mountains. There's not a lot of radar going on here, however CHP does rolling radar on these roads. What I've found after 3 or 4 encounters with CHP Ka C/O with the Redline on the "winding Redwoods" roadways here is still a decent 1/8th mile, round the corner alert. The thick moisture laden woods here with 60 to 75 foot tall Redwoods eats the radar - no reflection of bounce. Pretty much if you were to take a rifle and shoot randomly into the woods - the bullet would not travel very far as it would likely encounter a 3 to 4 foot diameter Redwood which stores a huge volume of water (which is why they also don't burn in forest fires and are able to survive for 2,000 years).
It's interesting that Redline still issues a nice alert in the forest - likely getting a bounce off the railing.
Near my domicile