Technology Wars: Cops Vs. Speeders
How Radar and Laser Detectors Work
Regardless of why drivers speed and cops ticket, each side is using technology to increase their chances of success.
How Radar Works
Back in the old days, officers "paced" speeders, following behind at a constant distance or timed speeders between two fixed points, calculating speed by dividing the distance by the elapsed time. The latter technique is still employed, particularly when aircraft are used in traffic enforcement. The invention of radar, however, changed the speeding game.
First used by the British in World War II, the operational concept of radar is simple: Radar essentially uses echoes and the Doppler shift to measure the size, speed, and even the contours of an object within its range. The ability to measure speed is what interests the police.
Their units emit radio waves that the operator aims at traffic. The waves bounce off the oncoming vehicle, causing an echo. The frequency of this echo can be measured by the radar gun. Because of what's known as the Doppler shift, an object moving more quickly toward the radar gun will reflect an echo of a higher frequency than one moving more slowly. The relative changes in echo frequency give the radar guns the data they need to calculate the target's speed.
The first police radar system debuted in 1947 and operated on S-Band (2.445 gigahertz), a frequency close to that of today's microwave ovens. The stationary-use, 45-pound units weren't particularly practical or accurate and their effective range was less than 200 feet. The next stage of development occurred in the mid-1960s with X-band systems (10.525 GHz). These newer units ruled the country's new Interstate system throughout the 1970s. The K-band (24.150 GHz) became more common after 1976, and the Ka-band (33.4-36 GHz) appeared in 1989. Because of their shorter waveform, these newer K-band frequencies enabled the radar units to operate with greater accuracy. Some 41 state police departments now utilize Ka-band radar systems. Reportedly, there are some 300,000 radar guns in operation across the US.
Today's police radar units can be stationary or mobile. They have the ability to clock traffic approaching the radar gun or driving away from the operator. Radar manufacturers recommend a maximum target range of around 700 feet, but the units are capable of locking onto a target at up to a quarter-mile if conditions are ideal.
As advanced as police radar has become, the units have some drawbacks. While fast, the emitting of waves and processing the echo can take the unit's computer seconds to lock in and register. This can take even longer if there are multiple targets, such as one might experience in traffic. The other problem is that when operating at 1000 feet, the radar "beam" can be 200 or more feet wide. This large coverage area reduces accuracy and can make it difficult for an officer to identify the target the radar unit has locked onto. Metal fencing, microwave radio towers, and other objects can cause also reflective interference and inaccurate radar readings.
How Laser Detectors Work
Laser or LIDAR (Light Detection And Ranging) equipment is the newest trick employed by police. Laser detection equipment works by aiming a narrow beam of infrared light at a vehicle, and then measuring how long it takes to reflect back to the unit. The computer in the laser unit divides the time by two and calculates the vehicle's distance. It then immediately repeats the process, comparing the change in distance to determine the vehicle's speed.
A burst from a laser gun can include as many as 1,000 samples per second, helping insure the accuracy of the measurement. Additionally, the beam of infrared light maintains its narrow focus, so it targets vehicles with pinpoint accuracy. From 1,000 feet, a laser beam measures just three feet wide. In other words, when an officer aims at a vehicle with a laser, chances are he'll get his reading.
One drawback of laser is that it must be fired from a stationary location. Unlike radar, laser cannot be shot through glass, and lasers are also impacted by rain, fog, dust or smoke.
Fuzzbusters and Other Countermeasures
While the first police radar systems came into use in the late 1950s, it wasn't until the '70s that speeders became armed with the first electronic countermeasures. Older drivers might remember the Fuzzbuster and Super Snooper, two of the earliest commercially marketed radar detectors. In contrast to the svelte, compact shapes of modern units, the first detectors looked like bulky, crudely built science fair projects.
Modern radar and laser detectors, such as the Escort 9500 IX, employ carefully shaped antennas to receive radio and light waves. When frequencies match those known to be used by police radar and laser units, the detectors signal an alert. But it's not so simple, because police aren't the only ones using the airwaves. Sensors that operate automatic doors at grocery stores also use various radar bands, as do garage door openers and traffic-flow monitoring systems.
Most units today combine radar and laser detection in one device, and conventional wisdom says a higher price tag corresponds with improved performance. The better detectors tend to do a superior job of filtering out non-police signals than cheaper units, and some models have built-in GPS, to help recognize and remember the locations of fixed-location "false alarms." One of the newest features being incorporated into the devices is unmanned photo radar and red-light intersection camera detection, often working in conjunction with a Web-based database of these locations.
The major shortcoming of driving with a detector, even a top-of-the-line model, is that there is almost no advanced warning when police use instant-on radar units or laser. If you get popped by instant-on radar, it's likely too late to slow down. Hearing an alert for laser is an even more dire situation, because the speed at which lasers operate means that by the time the detector sounds an alert, the laser gun is already showing the cop how fast you are travelling.
Keep in mind that radar detectors are illegal in Virginia and Washington, D.C., as well as parts of Canada. To sniff out citizens using the radar detectors, a manufacturer of radar and LIDAR units also produces a radar detector "detector." This works because all modern radar detectors use a component called an oscillator, which emits a measurable amount of electromagnet "leakage." This is what the detector detector detects.
Catching on to the pattern here? This is most certainly war.
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