DOES THAT MEAN YOU CAN DRIVE AT 70 IN 3RD GEAR IN A VIPER AND BE STOPED FOR A RECORDED SPEED OF 90 OR MORE??? That means I can drive my BMW cycle at the same speed as my friend on a Harley and he gets stopped?
Unless the computer program in this system has a recording of every vehicle in the world at every speed in every gear to compare against the vehicle in question, this is BS.

Don’t sweat it..easily defeated by simple modification to exhaust..I’ll get right on it.

Only stupid greedy ludite nazi bureaucrats would be naive enough to think that ingenuity won’t be used to defeat this too.

Civil disobedience..Right-on!!

TW, that’s obviously not how it works. Google “Doppler Effect”.

The Doppler effect works something like this; sound waves hit a stationary object at a faster rate than when it is going away. By comparing the rates, the speed of the object emmitting the sound can be calculated. It has nothing to do with the actual tone or sound coming from the moving object.

Don’t they have a better way of spending our tax dollars?

i suppse you could shift to a higher gear and slow down to screw up their system lol

This only works if vehicle is moving at steady throttle with no speed change. I doubt it will be accurate enough to be used as a legal speed trap, atleast for another couple of years.

This site seems to have a picture of Hitler for one of its headlines every few days. Isn’t there some other picture that you might be able to use?

Ok, how about a picture of Goebbels or Himmler or Goering?

Jon.

The Hitler looking guy compliments the heavy racism that frequently appers here in the LLN comments.

Because the measurements would be fractions of a second apart, the system could be accurate within a fraction of a MPH regardless of acceleration, current speed, gear changes, etc.

The only thing that this system provides beyond what is possible using current radar systems is an accurate way to detect spead while itself would be undetectable. It would also make it easier to detect the speeds of multiple vehicles at once.

I hope that they can compensate for air pressure, A dorp in air pressure or major rise in temperature can cause fulse readings. I don’t think by much though. Sounds nice.

you guys should look up the doppler effect..the intensity of the sound (i.e. loud exhaust) is irrelevant, they are measuring the shift in sound waves as you pass by the sensor (think of how a car sounds different after it passes you).

There are two problems with this:

1. As someone mentioned before, if you see the measuring equipment it and reduce your throttle as you pass it could measure a much greater doppler shift than it would if you had kept the same throttle setting. The error could be a much faster speed reading than you were actually traveling.

2. Winds will affect the reading. If you are traveling into a headwind the reading will be increased. Tailwind and the reading will be decreased. This may be solved by requiring that a wind reading be taken at the same time as your speed reading.

MM

This idea is not half as entertaining as the Google ads next to the article.

Free Radar Detector
Laser Radar Detectors
Find Detector Radar
Free Baseball Radar Gun

Do you think the Hitler image is really appropriate for this topic? I think not. Maybe showing a bit of support towards a certain raciest subject? I think so. Even if your not, I would hope so, it is clearly not needed and I ask you change it.

Thanks,
Joe

How is Hitler’s photo being racist?

As others have mentioned Doppler Shift is very accurate and it won’t matter if you have a loud dragster or a quit electric car. Some of you here need some science lessons. Why do you think Doppler Shift measurements are used to astronomy? You WILL NOT BE ABLE TO DEFEAT IT!

Everyone who thinks they can modify their exhaust or downshift, up shift or buy an electric car to get around this please go back to high school. The tires alone could provide enough sound to accurately measure the Doppler Effect of a moving vehicle.

I understand that the doppler shift will be able to detect your speed but, how is it going to identify who is driving or the make of your car? Don’t they still need a camera or something similar in order to verify what/who was speeding?

What’s the max speed you could measure using a common doppler effect detection device like they wish to implement? Surely it would be very very high?

Speed cameras can be bypassed if you have a car that can drive past them at 184+mph :p

The Doppler effect in sound speeds has a mathematical formula like this:

Frequency detected = [(Vsound +/- Vobserver) / (Vsound -/+ Vsource)] * Frequency source.

In this particular example we have a moving source but stationary observer. So, the equation is something like this:

Frequency detected = [Vsound / (Vsound -/+ Vsource)] * Frequency source

This machine works something like this:

It detects the Frequency of the sound produced from the car (any source is equally acceptable and proper) as it changes so, if we know the Vsound we can calculate the Vsource, which means we can calculate the speed of the car.

The ONLY problem here is this. In the previous equation we considered that there is no wind, so the velocities are absolute and no relative ones. If we want to be accurate all the time, we MUST calculate the velocity of the wind in real time. The differences are huge if we don’t calculate the wind velocity. Think that if the wind is to the detector lets say at 15mi/h then the speed measured will be 15mi/h higher than the real speed. If we consider that the wind is not the same even in a few meters distance the measurement MUST be done at very close distances (lets say 10-15m from the detector). Apart from this, the system has to be built with a machine that distinguishes the different cars. Lets say we have 5 cars very close together. How do we know which one speeds by only calculating a doppler shift (red or blue) ? It’s easy to have an officer read the results and using a radio inform the other officers that stop the offender. Another solution is to video record all the time and when a speeder is caught to see the video which one is going faster = he is the “criminal”.

BUT, all this stuff is a little too risky to be used in a court room. So, for the moment we have to wait until they come up with an idea that distinguishes the real speeder from the other drivers. When they do it, it will be the dooms day. The police can indentify ALL the speeders even in a highly used motorway.

Thnx for your time. Have a nice day from Athens, Greece.

Man you people are slow. If you don’t know what “Doppler Shift” is, please don’t make a post stating that it will be “so easy to defeat.”

Any car moving at highway speeds will make noise; even with the engine off, the doppler shift of the noise of the tires will be measurable!