Tested it out earlier today. It gives you around 3 seconds warning before a car passes you at a faster pace, and 5-6 seconds if they pass you at a slow pace. I had to heat and adjust the mount to point the sensor slightly to the right after I got home, as it tended to light up the red LEDs (indicating a vehicle is coming in straight from the rear) when the vehicle is still to the left.
The indicator placement location I chose is just okay. Ideally it should be placed higher in the line of sight even if they have to be closer together, but I have a huge screen in the way...
This spot (for the left side) would be a very nice location for the indicators, but it would be pretty horrible trying to shove the indicators through the vents from the inside:
View attachment 255996
Also, the red LEDs seem to be much dimmer than the yellow/amber ones, but it should be no issue if it's not under direct sunlight.