5 ms·

A great addition to this would be radar to track vehicle speeds. In my neighborhood we have an issue with jerks doing 50mph down our street(speed limit is 25mp

A great addition to this would be radar to track vehicle speeds. In my neighborhood we have an issue with jerks doing 50mph down our street(speed limit is 25mph) to bypass a traffic light on an adjacent street. Kids are often out and we've had a few near misses. Most of the offenders live nearby and I'd love a way to shame them into slowing down. The city is unable and unwilling to do any enforcement or install traffic calming on our street so we don't have any other options except moving.

criddell 9y ago
Would you need radar? If you have a camera pointed at the street, couldn't you use the distance traveled in successive frames to calculate a speed? If you already have one camera set up to record the tags, a second one should be easy to capture the speed.
- telot1 9y ago
  10 year veteran of the ITS industry here. It's not trivial to do camera speed recognition. You need to do ranging in addition to the video detection to know how far the vehicle is from the camera to accurately measure the speeds using movement between frames. These systems cost in the $10,000+ range, while a k-band doppler can be had for around $500. It's a no brainer to stick with the 1940's doppler technology ;)
  - ambicapter 9y ago
    Or could you just post two posts near the road in view of the camera with a known distance between them...
    - votingprawn 9y ago
      I wonder if you could even use road markings or kerb stones as your calibration to save the effort of measuring things out. I'm admittedly rather unqualified in this area (I don't even know what the ITS industry is!) but I have experience in estimating distances from video and calculating speeds from pixel displacement (particle image velocimetry) and at first pass it seems to me this would be a fairly straightforward problem to solve. Obviously radar or lidar would be preferable but a quick search for "OpenCV speed estimation" shows people having success with simple single <$50 camera setups.
      - logfromblammo 9y ago
        I'd use two infrared laser LEDs on a PCB with a low-res-but-high-speed infrared light detector, and set up a retroreflector across the street. If the LEDs are 10cm apart, and parallel to the street, and left dot vanishes 7.45645 ms after the right dot, then something was moving through the beams from right to left at 30 miles per hour (13.4112 m/s). If right dot vanishes 4.06716 ms after left dot, something was moving left to right at 55 mph (24.5872 m/s). You can even get an estimate of vehicle length and acceleration if you watch for the dots to reappear. The frame rates and resolutions of most cameras aren't great for precisely estimating speed. You would need a high-speed camera, which is wasted on a surveillance application. So you just use two cameras, one that sees 16 infrared pixels with an ultra high frame rate, and one that sees many RGB pixels at 24 fps.
        criddell 9y ago
        > The frame rates and resolutions of most cameras aren't great for precisely estimating speed. How good do you think the numbers would be? For example, the speed limit on my road is 25 mph but I know people routinely drive through at 40 mph. Would a camera system be good enough to record, say, 30 mph with error bars equal to +/- 5 mph?
        logfromblammo 9y ago
        That is highly application dependent. If you can set up clear distance markers 100m apart on the road itself, a regular surveillance camera set up with its line-of-sight perpendicular to the road could probably estimate speeds between 5 and 80 mph with at least 1 mph precision, and adding some image processing software could probably give you 0.1 mph precision or better. Oblique views, curved roads, unclear markers, or even differently colored cars could produce false results, or no results at all. It may be enough to convince your local cop shop to set up a radar trailer on your street for a few days, but you're not going to be convicting anyone of reckless driving with it.
        votingprawn 9y ago
        I reckon an RPi type camera would be perfectly sufficient to estimate speeds, probably to a higher accuracy than you ask. Edit: a quick search led me to this https://gregtinkers.wordpress.com/2016/03/25/car-speed-detector/ https://gregtinkers.wordpress.com/2016/03/25/car-speed-detec... and this https://github.com/pageauc/speed-camera https://github.com/pageauc/speed-camera
  - omh 9y ago
    If the street is long enough, what about two of these cameras with one at each end of the street? You'd only get an average speed but that should be enough to catch the worst offenders. Something like this[1] has been used on UK motorways for a while. [1] https://en.wikipedia.org/wiki/SPECS_(speed_camera) https://en.wikipedia.org/wiki/SPECS_(speed_camera)
  - PappaPatat 9y ago
    The most difficult aspect is the "getting the speed legally binding". As much as many a police officer would love to write a ticket based on your setup, little will become of it without solid formal proof of its accuracy.
    - criddell 9y ago
      It doesn't have to involve the police or courts to effect a change. If somebody asked me to slow down because I was driving at 40 mph down our 25 mph street, I would probably do it.
giarc 9y ago
Have you called local police? My neighbourhood had the same issue during some recent construction that lead to a street becoming a main thoroughfare. The neighbourhood committee requested assistance from police and they placed one of those radar/speed sign on trailers and also had more photo radar trucks set up.
naeemtee 9y ago
Hey! I'm building something that's pretty much exactly this, and I'm curious if your neighbourhood has some kind of community watchgroup that would want to try prototype something like this?

criddell 9y ago

Would you need radar? If you have a camera pointed at the street, couldn't you use the distance traveled in successive frames to calculate a speed? If you already have one camera set up to record the tags, a second one should be easy to capture the speed.

telot1 9y ago
10 year veteran of the ITS industry here. It's not trivial to do camera speed recognition. You need to do ranging in addition to the video detection to know how far the vehicle is from the camera to accurately measure the speeds using movement between frames. These systems cost in the $10,000+ range, while a k-band doppler can be had for around $500. It's a no brainer to stick with the 1940's doppler technology ;)
- ambicapter 9y ago
  Or could you just post two posts near the road in view of the camera with a known distance between them...
  - votingprawn 9y ago
    I wonder if you could even use road markings or kerb stones as your calibration to save the effort of measuring things out. I'm admittedly rather unqualified in this area (I don't even know what the ITS industry is!) but I have experience in estimating distances from video and calculating speeds from pixel displacement (particle image velocimetry) and at first pass it seems to me this would be a fairly straightforward problem to solve. Obviously radar or lidar would be preferable but a quick search for "OpenCV speed estimation" shows people having success with simple single <$50 camera setups.
    - logfromblammo 9y ago
      I'd use two infrared laser LEDs on a PCB with a low-res-but-high-speed infrared light detector, and set up a retroreflector across the street. If the LEDs are 10cm apart, and parallel to the street, and left dot vanishes 7.45645 ms after the right dot, then something was moving through the beams from right to left at 30 miles per hour (13.4112 m/s). If right dot vanishes 4.06716 ms after left dot, something was moving left to right at 55 mph (24.5872 m/s). You can even get an estimate of vehicle length and acceleration if you watch for the dots to reappear. The frame rates and resolutions of most cameras aren't great for precisely estimating speed. You would need a high-speed camera, which is wasted on a surveillance application. So you just use two cameras, one that sees 16 infrared pixels with an ultra high frame rate, and one that sees many RGB pixels at 24 fps.
      - criddell 9y ago
        > The frame rates and resolutions of most cameras aren't great for precisely estimating speed. How good do you think the numbers would be? For example, the speed limit on my road is 25 mph but I know people routinely drive through at 40 mph. Would a camera system be good enough to record, say, 30 mph with error bars equal to +/- 5 mph?
        logfromblammo 9y ago
        That is highly application dependent. If you can set up clear distance markers 100m apart on the road itself, a regular surveillance camera set up with its line-of-sight perpendicular to the road could probably estimate speeds between 5 and 80 mph with at least 1 mph precision, and adding some image processing software could probably give you 0.1 mph precision or better. Oblique views, curved roads, unclear markers, or even differently colored cars could produce false results, or no results at all. It may be enough to convince your local cop shop to set up a radar trailer on your street for a few days, but you're not going to be convicting anyone of reckless driving with it.
        votingprawn 9y ago
        I reckon an RPi type camera would be perfectly sufficient to estimate speeds, probably to a higher accuracy than you ask. Edit: a quick search led me to this https://gregtinkers.wordpress.com/2016/03/25/car-speed-detector/ https://gregtinkers.wordpress.com/2016/03/25/car-speed-detec... and this https://github.com/pageauc/speed-camera https://github.com/pageauc/speed-camera
- omh 9y ago
  If the street is long enough, what about two of these cameras with one at each end of the street? You'd only get an average speed but that should be enough to catch the worst offenders. Something like this[1] has been used on UK motorways for a while. [1] https://en.wikipedia.org/wiki/SPECS_(speed_camera) https://en.wikipedia.org/wiki/SPECS_(speed_camera)
- PappaPatat 9y ago
  The most difficult aspect is the "getting the speed legally binding". As much as many a police officer would love to write a ticket based on your setup, little will become of it without solid formal proof of its accuracy.
  - criddell 9y ago
    It doesn't have to involve the police or courts to effect a change. If somebody asked me to slow down because I was driving at 40 mph down our 25 mph street, I would probably do it.

giarc 9y ago

Have you called local police? My neighbourhood had the same issue during some recent construction that lead to a street becoming a main thoroughfare. The neighbourhood committee requested assistance from police and they placed one of those radar/speed sign on trailers and also had more photo radar trucks set up.

naeemtee 9y ago

Hey! I'm building something that's pretty much exactly this, and I'm curious if your neighbourhood has some kind of community watchgroup that would want to try prototype something like this?