Thursday, November 20, 2014

Speed Demons

Which radar detector is quickest to spot police radar?

Instant-on radar can easily clock speeders in less than one second.
Detector designers walk a tightrope, balancing speedy response with accuracy. A detector with a hair trigger may be the first to alert, but with little time to process a signal, it often gets it wrong. The result is a false alarm.

But a too-leisurely response also imposes risks. This is because modern police radar with DSP (digital signal processing) is commonly used in instant-on mode to evade detectors. It's kept on standby, not transmitting a signal. When a target of interest appears, with a button-press the officer can check its speed and return to standby mode, all in less than one second.

An MPH Industries radar used in POP mode is even quicker, accomplishing this in less than 0.07 second. By design, target speeds in POP mode can't be locked and MPH wisely cautions officers against taking enforcement action based on these snapshots.

That's because there's no time to establish a target's tracking history, required by radar case law to help reduce incorrect target identification—and bad tickets. Tracking history in moving mode—police vehicle and target both rolling—has more importance.   Added variables, particularly when traffic is heavy, increase the possibility that the officer unknowingly is eying a vehicle different than the one producing his radar's target speed.

Trouble is, lazy officers tend to skip the tracking history. Many trigger the radar, glance at the speed, then return to standby mode.  Many also shut off the radar's audio Doppler, a vital tool to make certain that both radar and officer are looking at the same vehicle.  Officers like this are the ones you'll want to avoid.

Most detector manufacturers have slowed response to cut false alarms, likewise making POP mode a user-selectable menu option. I wondered how many instant-on radar signals are being missed as a result.

To find out, I gathered up six detectors from four manufacturers. All were tested in Highway mode in their default settings.

Two radars were used: a Stalker Dual Ka-band and a Decatur Genesis II K-band radar, both operated in stationary mode. With a stopwatch and using the instant-on remote control, I first established the minimum signal duration each detector required before it would process a signal and sound an alert every time.

With that baseline established, I repeated the test 20 times for each detector on each band.  The average of each set was then calculated.
Quickest of the group was the Whistler CR75; it alerted reliably to K-band radar signals of 0.35 second duration and Ka-band signals at least 0.41 second long. The Cobra SPX 6700 was almost as fast.
The second-quickest in response was the Escort RedlineXR: 0.45 and 0.52 second, on K and Ka, respectively. (A standard Redline takes twice that long to respond to either band.)
The Escort Passport Max ignored K-band signals that lasted an average of less than 1.42 seconds. It was faster on Ka band though, alerting to signals averaging 0.68 second in duration.

The jury's out on which better protects against K band threats. BEL and Escort detectors are likely to miss some instant-on radar signals. On the upside, they will bark fewer K-band false alarms.

Cobra and Whistler radar detectors have less sensitivity than the pricier Escort and BEL models, imposing less of a penalty for quicker response.

In the end, user experience will dictate which is the better strategy. The bottom line is a tradeoff between fewer false alarms and better protection from instant-on radar.