Understanding Police Radar
To understand police radar, you need to understand a little bit of basic physics. Specifically, the Doppler Effect.
Wikipedia defines the Doppler Effect as “the change in frequency or wavelength of a wave in relation to an observer who is moving relative to the wave source.”
Basically, “when the source of the waves is moving towards the observer, each successive wave crest is emitted from a position closer to the observer than the previous wave. Therefore, each wave takes slightly less time to reach the observer than the previous wave. Hence, the time between the arrival of successive wave crests at the observer is reduced, causing an increase in the frequency. While they are traveling, the distance between successive wave fronts is reduced, so the waves "bunch together".
Conversely, if the source of waves is moving away from the observer, each wave is emitted from a position farther from the observer than the previous wave, so the arrival time between successive waves is increased, reducing the frequency. The distance between successive wave fronts is then increased, so the waves "spread out".”
RADAR stands for Radio Detection And Ranging. Basically, it’s designed to detect the speed-induced changes in the transmitted frequency of the sound waves of your car as it passes. The faster you’re going, the faster the soundwaves compact as you approach and expand as you drive away.
Most police radar devices work in one of two ways:
Continuously Transmitted/Constant-On (CO) – Essentially, the radar is always on, so it’s always detecting the approach of speeding vehicles. These tend to be stationary devices (speed readers) or police vehicles parked with a speed gun pointed at the road. These are harder for radar detectors to detect, and they tend to be located in concealed places.
RF-hold – Also known as instant radar, these are devices that are not permanently on, but are triggered to detect your speed. Many police radar guns are handheld devices that are RF-hold devices, that will only turn on when the police officer presses the trigger. These can only be detected when they are activated—usually, by the time your radar detector picks up the signal, the radar gun is already scanning you.
Most police scanners operate on one of three radio wave frequency bands:
X-band is the oldest of the radar bands used, but it’s being phased out in most parts of the country in favor of either K or Ka-band. The dispersion patterns tend to be very wide, and are typically reflected in many directions, giving the police a chance to cast a wide net for speeding cars. The good news for you is that the wide reflection means your radar detector has a better chance of picking up the radar transmission in time to warn you to slow down.
How Radar Detectors Work
You know that police scanners work by measuring the Doppler distortion of sound in relation to your speed. They use the above-mentioned frequency bands to scan for any cars going too fast.
Radar detectors, however, are designed to scan for those frequency bands. Any time the radar detector picks up radio waves being fired at your car, it will warn you that you are being scanned. The warning light on the radar detector should, in theory, give you enough time to slow down before the officer scanning has a visual confirmation (or LIDAR confirmation) that you are speeding.
It’s important to understand that not all radar detectors are fully accurate. There are things that can cause false positives, including adaptive radar cruise control (common on newer vehicles) and automatic supermarket doors. These things use similar radio frequencies, which your radar detector will pick up and set off a false alarm.
Note: Many police officers will use both radar and LIDAR, also known as laser scanners. Laser scanners are much harder to detect, as they use a narrow beam of light to point directly at your vehicle to measure your speed.
GPS vs. Radar and Laser Detectors
Most laser and radar detectors are designed to warn you when a LIDAR or RADAR gun is being pointed at your vehicle. They pick up on the frequency of radio transmissions and light beams in order to alert you to the presence of police scanning.
GPS detectors, however, are slightly different. They offer access to a database of recorded locations of fixed cameras and speed monitors. When your vehicle’s GPS signal approaches the GPS location of these fixed cameras, they will alert you to the presence of the cameras so you have time to slow down before you get a ticket. (Bonus: they may also be able to alert you to school locations and accident blackspots).
The beauty of GPS detectors is that they help you to stay on top of all the fixed locations where you could get a ticket. You may find there are a surprising number of hidden camera locations around your city, and you could end up with many tickets every year simply because you didn’t know about the camera.
However, GPS detectors won’t be able to tell you if a police car is posted up under the next overpass or tucked around a corner.
Are Radar Detectors Legal?
In the United States, it is illegal to use radar detectors within Washington D.C. and Virginia. Philadelphia, New Jersey, Florida, and California all have laws that prevent you from hanging anything from your windshield, meaning you have to mount the radar detector on your dashboard or console. In the rest of the United States, there are no laws that prevent you from using radar detectors in personal vehicles.
Radar jammers, on the other hand, are illegal. It is a federal offense to use a radar jammer, and the consequences can be severe.
Laser jammers are illegal in many of the 50 states, though some states have not outlawed them.
Outside the U.S., the laws are equally varied. Most Canadian provinces outlaw radar detectors, with only British Columbia, Saskatchewan, and Alberta permitting them. They’re fully legal within the UK, Italy, Russia, Ireland, and Norway, but they are fully prohibited in France, Switzerland, Austria, Portugal, Sweden, and Finland. In Germany, Poland, Denmark, and Spain, you are allowed to own a radar detector, but their use is prohibited.
Radar Detector Buying Guide
If you’re looking into buying a radar detector, it’s worth knowing what sort of device works best for your vehicle and your situation.
There are three types of radar detector to choose from:
- Cordless – These are mounted on your windshield, usually using suction cups. They are battery-powered and thus require no outside power source.
- Corded – These are also mounted on your windshield, but they do require an external power supply—typically plugged in via your cigarette lighter port.
- Remote-mount – These are permanently mounted to your vehicle, and they’re nearly impossible to spot from the outside of your vehicle. However, they cannot be moved from one car to another, limiting their use to just one vehicle.
When shopping for radar detectors, there are a number of features to consider:
Laser Detection – This feature ensures that your radar detector picks up laser signals beamed at your car. It’s important to note that it will ONLY pick up signals in front of you, not from behind or to the sides.
Some radar detectors come with 360-degree laser detection, which is much pricier but far more effective at protecting you from LIDAR signals.
RDD – In places where it’s illegal to use radar detectors, police have special radar detector detectors, devices designed to pick up any traces of radar detection. They pick up on the oscillations emitted by the radar detector receivers.
The good news is that some radar detectors come with special built-in fail-safes that detect when RDD devices are being used and will automatically shut off. VG-2 and Spectre are the two types of RDD technology used to scan for radar detectors, so consider getting a device that has both VG-2 and Spectre shielding.
City and Highway Modes – Most radar detectors are set on “highway mode” by default, as that’s where most people use them. They operate with the widest range of detection possible, thus giving you the best chance of picking up distance radar signals.
However, if you’re going to be driving in the city, you’ll want to find a radar detector that comes with a “city mode” built in. This mode reduces your range of sensitivity, reducing the risk of false alerts from non-police scanner sources of radio frequencies (such as automatic door openers).
Alerts – There are two types of alerts: voice and visual. Visual alerts involve a flashing light that warns you that you’re being scanned. This is ideal for night driving or if you have sleeping passengers. However, it requires you to take your eyes off the road.
Voice alerts, on the other hand, may make noise, but they will let you know that you’re being scanned without your needing to take your eyes off the road. They’re much safer to use, so they’re a good built-in feature to look for.
GPS – As explained above, GPS won’t help you look for police cars or motorcycles set up to scan the roads. However, they’re great for warning you of approaching speed cameras, speed traps, and school zones.
Some GPS-enabled radar detectors are even able to “remember” locations where you were scanned in the past, and they can set up a warning to remind you to slow down in areas where there are likely to be police.
Instant-On Protection – Most police guns use Instant-On or RF-Hold radar, which means there is only a very short window (seconds) when the radar is active and scanning. If the police point it at your car and scan, there’s nothing your radar detector can do to warn you in time.
However, Instant-On Protection is a feature that uses highly sensitive K-band reception to alert you to the presence of Instant-On scans pointed at the cars around you. It may only give you a few seconds of warning, but it may be enough to help you reduce your speed in time to avoid a ticket.
Smartphone Apps – More and more radar detectors are being manufactured with smartphone apps for your iOS and Android devices. These apps allow you to mark law enforcement GPS locations, or receive alerts and warnings. Some are designed to work via Bluetooth, making them smaller and more easily concealable.
How to Make the Most of Your Radar Detector
If you’ve just bought your first radar detector, here’s how you can use it as effectively as possible:
- Mount it right – Make sure your radar detector is mounted in a location where it has a clear view of the highway or road ahead, and where it is easily visible to you without your turning away from the road. Mount it away from the radio antenna and the windshield wipers—make sure it’s mounted in an unobstructed location, typically on your dashboard. Mounting it higher won’t improve laser or radar detection, but will simply obstruct your view.
- Learn its alerts – Each alert has a different significance: X-band alerts are false alarms in every state except Ohio, K-band alerts are as likely to be Blind Spot Monitoring devices in nearby cars as they are to be police scanners, but always take Ka-band alerts seriously, as that is the band most police scanners use. Even if the K-band or Ka-band alert is faint or disappears quickly, take note: it may be an officer shutting off his scanner to avoid detection.
- Protect your detector – You spent $100+ on the radar detector, so don’t leave it lying around in your car. Hide your detector in your glove box or under the seat so it’s not immediately visible. Thieves know they can make a pretty penny selling used radar detectors. Also, in the heat of summer, the bright sun can bake the plastic casing of your radar detector. Keep it out of direct sunlight when not in use.
- Spend a bit more for GPS – Not only will GPS positioning help you to avoid speed cameras and speed traps, but it will record locations with false alarms, thereby reducing false alarms in the future. It will also track places where radar was detected so it will be more sensitive next time you pass that location. Plus, GPS detectors can actually store the signal frequency and lock it out so it won’t set off the false alert next time.
How to Avoid Speeding Tickets
Using a radar detector is a good way to avoid speeding tickets, but it’s not your only solution! Here are a few tips to help you out:
Follow the crowd – Never be the vehicle out in front of the pack. Go with the flow of traffic, and match your speed to that of the vehicles around you. As long as you aren’t the fastest vehicle or in the front, cops are far less likely to single out your vehicle.
Stick to your lane – Even if you’re going a few miles above the speed limit, you’ll find that sticking to one lane is the best way to avoid drawing the police’s notice. Most of the time, they’re looking for people who are driving recklessly, which means speeding and making crazy lane changes. As long as you’re sticking to one lane and driving no more than 5 or 10 above the posted speed limit, you’re far less likely to get a ticket.
Learn the speed traps – Every city has speed traps, and there are locations where police love to sit and wait for speeding drivers. Do some research to find out these locations, and be wary when you approach them. Learn the speed traps along your daily commute so you can drive carefully.
Slow down – This is the simplest and safest solution of all! There’s no need for you to drive above the posted speed limit on highways, so consider moderating your speed to that safe limit. Yes, it will take you a few more minutes to get where you’re going, but you’ll reach your destination alive and without speeding tickets.
Learn to use your radar detector – If you’re going to invest in a radar detector, it’s worth learning how to use it. That means reading the instructional manual and getting the hang of the various features and functions. Take a few minutes to sit down and read over the manual carefully before using it. You may just find that the instructions will give you insights into the best practices and most effective methods of use to ensure maximum effectiveness.