please help me about my ultrasonic project!please

hi everybody excuse me Ihave a project about ultrasonic for measurment of distance beetween two cars! its not for avoidance of hit!it for reducing the speed to keep the
standard distance between two car somy need is about 30 or 40 meters its very long distance but its two neccessary for me how can I do it I read somthing about horn but its .... you know its in a car! what a horn can be our what a car???? accept my special thanks for your helps
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Ultrasound will not work well for this. Typical vehicle separation distances are too large, and it won't work well in rain, snow, or high wind conditions. You should use radar like everyone else.
Google for "adaptive cruise control".
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Hi,
Ultrasonic is not appropriate for this application. You should look at the RADAR options.
You may start with the following URLs; http://en.wikipedia.org/wiki/Radar http://www.williamson-labs.com/autordar.htm http://www.ieeconferences.org/Events/Hoare.pdf http://www.hamhud.net/darts/rdr_comp.htm http://www.shfmicro.com/gunn.htm http://www.upv.es/menuconf/CD%20MENU%20CONFERENCE/Poster/jose_m_zamanillo_2.pdf http://www.autocruise.net http://www.autocruise.net/MMIC-GUNN%20 (English).pdf http://www.epsilonlambda.com/#CW
Cheers,
Miem
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Miem wrote:

I have an Eaton VORAD radar sitting on my desk, pointed out the window at an intersection. You get range, range rate, and azimuth for car-sized targets. It was at one time fun to watch the cars go by. We used one of these on the Overbot in the DARPA Grand Challenge, as a backup to the more sophisticated sensors, and this was an extra unit used for debugging.
This is an older device; it's more of an emergency warning device than something useful for speed control. There's been progress since the VORAD, which is mid-90s technology.
                John Nagle
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