Radar On The Roads

Radar on the Roads Mazhar M. Chinoy Most Pakistani roadsters who have traveled on local highways and motorways have probably witnessed speed radar guns – equipment threateningly poised at oncoming cars not unlike a rustic old tripod box camera, manned by one or two policemen and generally perceived as an irritating kink on speedways that can get them into trouble with the law while speeding beyond the assigned limit. The concept may be relatively new on the domestic circuit – the invention is however, more than 50 years old, a product developed by Decatur Electronics in the USA in 1954 and inducted into the American police force the same year. Radar guns were invented with a simple concept behind them, nothing more than the mere transmitting and receiving of signals and that is exactly how the contraption works A radio signal is sent out by the gun that bounces off objects and is received again, albeit differently. The difference in this frequency is calculated by the Doppler Effect – analogous to how a siren sounds and recedes as the vehicle approaches and passes the onlooker - and measures the speed of the object rather accurately. Radar guns these days do not need to be stationary and can compare the frequency shift between received images instead of the frequency shift between sent and received frequencies, enabling equally accurate measuring of speeds with a moving radar gun Traffic radar guns can be hand held, stationary or mobile. Hand held units are normally battery powered and mostly stationary, mounted inside police vehicles, or even outside of the vehicles while discretely hidden around a curve or behind small mounds of dirt to catch unwary speeding motorists. How many times have we seen policemen with ominous looking radar guns around a bend or under the cloaking premise of an overhead bridge. Motorists will be wary of technology as more sophistication sets in. Now available in the market are intelligent, tech-savvy machines that can track vehicles approaching and receding both in front of and behind the patrol vehicle. They can also track the fastest vehicle in the selected radar beam, previously difficult and errorprone, from both the front as well as the rear of the police car. The speed radar's effectiveness is wholly dependent on two things: the strength of the transmitted signal, and the reflectivity of the target. The greater amount of power put into the machine entails a higher cost which has its own implications for the departmental budget. Radar reflectivity is mostly an issue of size and shape. The larger the vehicle, the easier it is for radar to pick it up and bounce off it. An ideal vehicle type that sets the policeman adrenalin running is huge with flat surfaces. But with most cars on the road these days being smaller and designer focus increasingly on curvaceous body, the sheet metal is generally not flat. This reduces the "visibility" of the car to the radar signals. While radar guns tend to measure an object’s speed very accurately, the machine is also dependent on user expertise. In most machines, the vehicle whose speed is desired ideally should be the only moving object within the radar beam. Thus, on a busy stretch of road, user application is critical for a correct reading. This issue is more or less circumvented in newer machines that are capable of picking out and tracking the fastest vehicle among others. Another downside is erroneous readings creeping up due to interference in the radar band by cellular phones, other transmitters, power lines and even road signs along the bandwith. Mobile radar guns readings are also known to have been impacted by the police car’s fan heater movements! In the end, a significant lot depends on the human element. Motorway Police generally undergo

rigorous training in the best possible operation of police traffic radar that includes the setting up and testing the equipment as well as correctly identifying target vehicles. Training in the visual estimation of speed and distance is another feature that vastly reduces chances of error in all fairness. While the average Pakistani’s interest in speed radar guns of late has jumpstarted primarily because of cricketing fervour, these guns are more than machines to measure the budding or aging fast bowler’s speed. They have an increasingly significant role to play towards the prevalence of sanity on Pakistan’s dangerous highways, and are hopefully here to stay