K40 RLS2 Radar Detector Review

I hadn’t used a radar detector in many years. After writing all about it, K40 Electronics offered to bring me up to speed on the latest and greatest technology, and sent me their RLS2 detector.

(Full disclosure: K40 provided the RLS2 at no charge for this review. I also reached out to Escort and Valentine to make this a comparison test, but they never got back to me.)

Unlike other reviewers, I have not been a habitual radar detector user. I tried them years ago, and found that nine times out of ten, they alerted me to automatic door sensors, or security systems, or electronic road signs. That’s why I stopped using them. Besides, maintaining situational awareness, and, more recently, watching for police alerts on Waze, has kept me (mostly) out of trouble for years.

My original article exploded on Oppositelock. While many comments agreed with me, some opposing comments made excellent points. One of them was that the filtering technology of modern detectors is much better than the ones I used in the past, resulting in fewer false alerts. Another, in response to the inevitable “If you don’t want to get a speeding ticket, don’t speed” comments, pointed out that sometimes a detector can help prevent you from making an honest mistake. I know that when I switch from my Subaru BRZ to my wife’s Ford Flex, the combination of its more refined ride and powerful 3.5 EcoBoost motor means that I sometimes don’t realize just how fast I’m going sometimes. A blip on a radar detector, whether it’s a speedtrap or just an unrelated sensor, reminds you to check your speed and keep it where you intend to. And then there’s the issue of certain municipalities that use their police force as auxiliary revenue collectors. Speed limits are supposed to be set at the 85th percentile speed, meaning that only 15% of all drivers exceed it. Yet on the MacArthur Extension in Springfield, IL, 90% of all drivers are exceeding the incredibly low speed limit immediately after exiting the interstate. That’s how they get you, and the cost of a speeding ticket and several years of insurance surcharges could more than cover the cost of a decent radar detector to save you from this fate in the first place.

I tried to be clear in my original article that I’ve never been against the use of radar detectors. I’ve simply chosen not to use one myself. I have an open mind, and I welcomed the opportunity to try the best portable radar detector that K40 offers to see how the other half lives.

K40 RLS2

In the box, there’s the detector itself, a simple but effective suction cup mount, and two power cords – one long and straight, the other shorter and coiled. I stuck the RLS2 to the top of my windshield next to the mirror, and used the long and straight cord for a hidden install running above the headliner, down the pillar, and into the glove box. My BRZ has a handy power port there that must have been designed with this application in mind. This also means that I can take the RLS2 with me and use the coiled power cord in temporary installations, such as in my wife’s Flex.

I decided to begin my RLS2 adventure in Highway mode with all bands enabled and all filters disabled. A trip to the Mall at Whitney Field in Leominster, MA showed me this was a bad idea. I got numerous X-Band and K-Band false alarms, just like my old detectors did. But unlike my old detectors, the RLS2 provided some options to deal with the false readings. Pushing the Quiet Ride button will disable all audio alerts until you exceed a particular speed that you define, at which point it will resume normal operation. In my case, turning on the Traffic Sensor Filter eliminated all of these false alerts. It’s actually intended to filter out highway traffic flow sensors, not shopping mall radar sources, but in my case it worked for that, too.