This is pretty speculative - but was looking for other opinions.
I drove round trip through Nevada via I-80 over the Thanksgiving holiday.
There was an unusual increase of alerts (to be expected over a holiday), MOST of them I identified the location.
Keep in mind this is I-80 in the desert. No cross streets, just a single ribbon of pavement going East-West. On several occasions, I got a Ka hit which was steady for a minute, then increasing over time. Maybe it lasted 2 or 3 minutes, then "poof", gone and did not come back. I carefully watched opposite direction traffic - nothing. The detector never got to full scale alert. I looked everywhere, no one getting pulled over, nada. Also - in this neck of the woods you can see a LONG ways front and back.
Westbound I-80, Mile Marker 401, Nevada
I never figured out the source. The only one I came up with was a LEO was approaching from WAY behind me and I was getting bounces off the back of tractor-trailer rigs or hillsides, and the LEO made a U-Turn in the median. I'm using a Redline which can pick up a signal from pretty far away.
The only thing is - I had a few of these hits that were there for awhile, then went silent. I usually try to figure out such things, but in those cases, I had to mentally "walk away".
Yeah - at times like those, would be nice to have the arrows.