SPEED CAMERAS

PRESENTED BYGIRIJA SANKAR DASHEMBETICS SOLUTIONS

CONTENTS INTRODUCTION INTRODUCING THE DOPPLER EFFECT FROM THEORY TO PRACTICE HOW WELL DOES IT WORKS

Operating during the rain and mistMeasurement rangeReaction timeContinuous transmissionDiscrimination

ON THE WRONG SIDE OF THE LAWThe need for public communications

COMMUNICATIONS AND PUBLIC AWARENESS CONCLUSION

There are many different factors that lead to traffic collisions and

casualties….

The main reason is………..

SPEED OF VEHICLES

INTRODUCTION

We use traffic lights and other trafficmanager to reduce the speed. One amongthem is .The speed cameras are used to identify

and prosecute those drivers that pass bythem when exceed the stipulated speedlimit.

INTRODUCING THE DOPPLER EFFECT

If a railway engine moving fast with itswhistle blowing is approaching anobserver, the pitch appears to becomemore. The pitch of the note appears tobecome less just as the engine movesaway from the observer on theplatform.

The apparent change in pitch due to relative motion between source and observer is known as…………….

Doppler's principle

What is Doppler’s Effect?

Doppler Effect: The principle of this effect is wellknown in the study of sound. It is known that if thesource of sound, emitting a note of frequency 'v' ismove with a constant velocity 'V' relative to anobservers, it is found that the observers perceives asound having the frequency v' which differs from 'v',being greater or smaller according to the source ismove towards or away from observers. Thisphenomenon in sound was first explained byDoppler and hence the name

The principle of speed camera that isthe Doppler's effect can be described bythe formulaf M = 2vfEcos(α/c)

where FM if the frequency of the received signal v is the speed of vehicles f E if the frequency of transmitted signal α is the angle between the transmitted signal and path along which the

vehicle travels c is propagation speed of the signal in the air.

The Doppler Effect

The sensitivity of the RADAR increases as theangle between the beams and the path of thevehicle decreases. For this reason the aerialsof speed cameras positioned parallel to theroads rather than across them! This is also thereason why only some types of RADAR canwork along bends, since the angle betweenthe beams and the vehicle continuallychanges, creating error the measurement.

FROM THEORY TO PRACTICE!

The basic of every speed camera is aSHF generator, which can transmit thebeams in specific directions.

HOW WELL DOES IT WORKS

Operating during the rain or mist:When it rains it comes down vertically

which is right angles to the RADAR beam,bringing about a Doppler effect of zero(cos 90=0 so Fm=0).Since mist doesn't move with respect to

RADAR beams it will be practicallyinvisible to the receiver and themeasurements are completely unaffected.

Measurement Range:Depends on two factors:-the power of SHF oscillatorsthe sensitivity of the detector.

Reaction time:Older models required by about half a

second to take a reliable measurement.Current models uses special DSP

algorithms with the very short time,making extremely fast readings possible.

Continuous transmission:RADAR does not need to have its

oscillators functioning continuously. It only needs to be active long enough to stabilize and take a measurement. Actual RADAR equipment works on the random basis or is activated only when a vehicle comes nearby.

Discrimination:When several vehicles traveling at

different speeds encounter at the RADARbeams the resulting Doppler signalcontains a mixture of signals at differentfrequency.There are however newer systems that can

measure the speed of the several carsimultaneously without discrimination.

ON THE WRONG SIDE OF THE LAW

There are two types of 'anti-radars‘:Jamming devices-The jamming devices are

simply SHF oscillators, which are used tosend ' take ' signal to the speed camera, theelectronic circuit in the radar can detectsuch jamming signals and notify the police.Detectors-A detector on the other hand

consists of the simple SHF receiver. Theseare relatively simple circuit containing amicrowave detector an alarm.

If the oscillators of the speed camera is set to a frequency that is outside the range covered by the detector, or it uses an optical laser, then you are bound to get caught.

COMMUNICATIONS AND PUBLIC AWARENESS

The need for public Communications:We should make people aware of the

speeding and benefits of speed cameras. We should make awareness in the local level, national level and also in government level.There are many publicity campaigns, for

example called ‘THINK!’ which includes messages about the risks and other consequences of speeding.

CONCLUSION

In general speed camera are perceived to be good idea because they protect innocent road users and pedestrians.So on utilizing the strategies in the right

way, we can reduce 40 percent it of accidents

THANK YOU