WTF! Speed traps don’t save lives, but they sure make money. Where’s that video of those Atlanta kids who drove 55 down some major thoroughfare and backed up traffic for miles?

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.

How can this method be accurate -one model of a ar with automatic willhave a differt ratio than the same modelcar with a 5 speed straight shift -Also depending upon the varius modlesina range, some will have differnt tire sizes – rsulyting in different overall ratios and engine speed.
keeping track of all this for each aer of car modle will take a library of some million vehicles -

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!!

“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.” – TW

This is incorrect, if you read it again, it talks about the exhaust sound’s Doppler Shift, not the volume of the exhaust itself. The Doppler Shift will allow the radar to calculate the speed it is traveling.

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

And what about electric cars? They don’t have an exhaust pipe!

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?

You can still “hear” an electric car though. There is a roar. Heck, the thing could measure a bee going by if it was calibrated to do so.

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

Thank you.

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.

i’ve just become stupider from this idea…

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?

Well, it seems to me… they’re still going to have to have some sort of camera to record your license plate number…

So why not just get one of those license plate sprays/covers that defeat cameras? Not sure if those products actually work, but if they do… their fancy machine wouldn’t be able to fine you.

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

Jon.

The infamous Big Brother in Orwell’s novel 1984 was described as having a mustache. Orwell covered the Spanish Civil War during the same time Hitler’s power was cresting, so the resemblance is probably not a coincidence. Still, the spectre of Big Brother (the literary character manifest) haunts us plenty in the motoring world. Sonic speed traps?

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

Seems like it would be much easier to defeat than a radar.

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.

This is a good thing. If it works and is widely implemented, it will kill the radar detector market. Radar detectors should be illegal everywhere anyway. It makes no sense that a device which serves no purpose except to facilitate breaking the law would be legal.

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.

I love scientific ignorance!! 6ix has the right idea. the wavelength of sound (or any other wave source) is shorter by an amount proportional to the speed of the object emitting the waves as it moves toward an observer. The converse is true for sound-emitters traveling away from the observer. The result is that higher pitches are heard as an object approaches, and lower pitches are heard as the object recedes. The difference in tone is therefore directly correlated to the speed of the object. No “library” is needed.

For what it’s worth, this is the same principal that astronomers use to measure the speed at which the universe is expanding, as red and blue shifts in light (due to objects traveling away and toward us, respectively) emitted by stars are also due to the doppler effect.

I wouldn’t worry about this being implemented in practice though, knowing your speed is worthless if they can’t ID you, and that simply couldn’t be done based on sound alone. Some other information would be necessary to achieve that.

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).

No radar detectors should not be illegal. If the government has the “right” to watch us, we have the right to know that they are doing so. Especially since speed limits are often only enforced so that the government can make a quick buck on someone without doing the unpopular thing (raise taxes). An idea to defeat this would be a jammer, just like a laser jammer. The device could emit sound waves at all frequencies to confuse this SONAR system (which is what this doppler system is FYI – SONAR = SOund Navigation And Ranging, RADAR = RAdio Detection and Ranging, LIDAR (or laser) = LIght Detection And Ranging). All use some sort of energy wave and all are defeated by jamming. I am certain that the Navy has had such a device for years. Power to the people!

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

Why fix something that aint broke?

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

It figures out how long it takes for the same sound wave to reach the microphone. It has nothing to do with transmission or exhaust or anything else. It can listen to the wheels.

Keep your eyes closed and have someone ride by on a bicycle and see if you can guess the speed from the sound of it going by. It has nothing to do with trans or windspeed or anything like that.

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

Boy people really run their mouth off when they think they know what they are talking about. Everyone seems to think that this is based on the volume of the exhaust. As one other poster already said this is based on the doppler shift, the change in pitch of the exhaust. Big difference from the volume. And no they still will NOT have to sample every vehicle at every speed, in every gear to be acurate. The system knows what the pitch was before it passed (cuz it can hear it) and then calculates the difference once it has passed, and thus calculates the speed.

How is Hitler’s photo being racist?

interesting about the big brother image… the post before my previous post has disappeared… weird… big brother is watching us!

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!

http://en.wikipedia.org/wiki/Doppler_effect

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.

Humph… At least people could ‘tamper’ with these devices, you can’t take the radar gun out of a cop’s hand… not that I’m suggesting anything.

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?

I love modern technology.

Let’s hope no one in government figures out how to mount radar, laser and doppler shift radar with cameras in fixed locations as they do in Europe.

I’d like some train-based public transit upon release of this technology please, Mr. President, so I can choose the days I risk getting ticketed driving my above average vehicle on subpar roads designed for 1980’s safety standards.

Máta ferðina á bilinum út í frá ljóðinum frá honum

Lærdi háskúlin í Tennessee hevur mennt eitt nýtt slag av fartfellu, sum mátar ferðina á bilum út í frá ljóðinum tá teir koyra framvið. Mikrofonir taka upp ljóðið av bilunum, eitt telduforrit eyðmerkir hvønn einstaka bil; og teir máta so ferðina út í fr…

I find the best way to not get caught in speed traps is to NOT SPEED.

(or speed REALLY fast so they won’t bother chasing you down.)

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

I meant the Gatso film cameras^ Not sure about the new digital ones.

And yes, fixed location sonar speed detectors would be a pretty inescapable detection – but what’s the max range?

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.

interesting.. i wonder if it is listening ONLY for exhaust, not wind roar or tire noise or just the sound in general. If it’s listening only for exhaust sounds, then if you shift into neutral, the tire and wind noise would overcome the sound of an idling engine when rolling at speed… and that should whack it out no?

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!

Like I said why fix something that aint broke?