So, it takes around 3/10ths of a second to get a good speed reading off of a RADAR unit. The average person's reaction time is about 3/4 of a second, so by the time you see me and react, its WAY too late. Actually, jamming on the brakes simply helps confirm my speed estimation. Especially if a large vehicle, like a semi-truck and a small sedan are giving conflicting readings and it's hard to distinguish which is doing what. As soon as the faster vehicle jams the brakes, it's super obvious and the ticket writing begins. Good RADAR units have a function called "fastest speed" which eliminates the stronger signal for the faster one, again, making it easy.
Stationary vs. moving and instant-on vs. always-on RADAR? Unless I was assigned to a specific area for speed enforcement because of a complaint, increase in crashes or whatever, I much preferred moving RADAR. Being stopped in one place waiting for people to come to me was boring. I ran with my signal off and my hand on the button. Some people will just turn their unit on and leave it on. Those are the ones hoping the RADAR detector equipped crowd will have enough influence on the cars around them to get them all to slow. Around here, it is very much about voluntary compliance as opposed to revenue generating, so if people slow down and I don't have to get out of my car, sometimes that's a good thing. Depends on my mood. It is true that local cops with jobs besides traffic enforcement will let higher speeds go, may run always-on more, and may be more chill. They have other calls and work to do as a main job, so traffic enforcement may be secondary. Highway Patrol units and dedicated traffic units will be more apt to run instant-on, and will cut less breaks.
There is absolutely no "cushion speed" required. My best friend and I arrested Texas' 3rd most wanted for doing 3mph over on the freeway at 0200. I've seen citations for 2 and 3 over written a few times. Usually, they're looking for other crimes, but the speed limit is defined as "The maximum allowable speed under the road's best possible condition." The "best condition" is subjective, but if it's dark, raining, too hot, too cold, or there's more than one car on the road, that stretch of road is not at its peak condition.
LASER is ok, but can be a PITA. It requires the unit be stationary because of the way it works. It is very accurate, and I've never yet seen a 'laser jammer' work as advertised. Its been a few years but every time we taught a class, we'd go buy the latest-greatest jammer we could find, and pull speeds off of it all day. I had some buddies that managed truck stops and electronic stores, so the returns of the "lightly used" malfunctioning units was easy. If I was assigned to a certain traffic enforcement position, I used my LASER. It was a very useful tool, as was the stopwatch setting on my Kustom Golden Eagle. I LOVED stopwatch.
These days, I don't write as many tickets. I have other stuff to do. Depends on the day, my mood, and a driver's actions as well as their attitude. I have a BEL9500 detector that I absolutely love. The range is amazing. New cars make it false, and it has scared the crap out of me a couple times. It also falses LASER in certain sun light. However, I have had bad luck with Escort products so have not used one in years. I've been very lucky with Bel so have chosen to stay with the brand. It's not like I'm ever really unreasonable anyway, but I don't want to risk running into "that" guy who is saving the world one ticket at a time. I'll say, if your unit goes off, check your surroundings until you're sure it's either false, doesnt pertain to you, or you pass the sender. That will greatly limit the amount of time you spend parked with a small parade parked behind you and a handsome/pretty public servant standing next to you with a stern look on their face!
