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Bicycle Radar Reflector

Get detected by traffic lights
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There is a set of traffic lights on my way to work which is controlled by microwave doppler radar detectors (the little camera-like boxes atop the pillars). Late at night, these lights go into a "responsive mode", whereby all lights stay at red until a vehicle is detected, whereupon the lights change to green before the car slows down for the red light, to "wave the car through".

Unfortunately bicycles are too small a target for these detector. A cyclist approaching a red light will ease off, in anticipation of the change to green. The result is that by the time your are in detect range, you're going too slowly to trigger the detector, which has a velocity threshold. The result is that bicyclists are left waiting for a car to pass before they can go through the junction.

I propose a plastic sheet, the back of which has cubic facets moulded into it, and is plated with nickel or some other metal. This creates an array of "corner cubes" which are like microwave catseyes, reflecting any incident radar straight back to the detector. This increases the detected signal strength, allowing cyclists to be detected while they are till moving at 10mph. It could be incorporated into those reflective yet deeply unfashionable "safety belts" at very little cost.

Alternatively, to put a cool gadgety spin on this idea, simply modify the classic Chinese bicycle bell. Instead of a metal bell, there is a gay plastic cover (transparent to microwaves). When the lever is pushed, a sector gear spins a disc fitted with a number of discrete corner cubes. The peripheral speed could easily be 30mph. This has the effect of raising the velocity detected by the doppler radar unit, further increasing your chances of detection, and allowing detection even when stationary. It could be sold as a sort of "remote control" for traffic lights, for the cyclist who has everything.

shameless_self_reference, Oct 04 2002

(?) My homework www.utmc.dft.gov.uk/utmcr1/pdf/utmc24.pdf
Recommended reading for hardcore traffic detection buffs. Complete with some gorgeous (though quite explicit) pictures of traffic lights topped with unmistakeably "camera-like" doppler radar detectors [shameless_self_reference, Oct 05 2002, last modified Oct 06 2004]

His homework, this time with a working URL http://www.utmc.dft...mcr1/pdf/utmc24.pdf
[This is a link to a 490Kb .pdf file] On page 33 there is a quote that says that "narrow-beam doppler radar or Passive infra-red detectors is commonplace for the detection of [bi]cycles in a dedicated lane." [bristolz, Oct 05 2002, last modified Oct 06 2004]

SCATS http://www.mrwa.wa....lications/scats.htm
The traffic signal method used across Australia [CrumbsDM, Oct 05 2002]

Radar flag http://www.radarreflectorflags.com/
perfect for a bike; sounds halfbaked but ain't [FarmerJohn, Oct 05 2002, last modified Oct 06 2004]

Senster Cybernetic Sculpture http://home.iae.nl/...oluon/senstere.html
Used doppler radar to react to people. One downside of my idea is that it could be used by malicious children to frighten Sensters. [shameless_self_reference, Oct 06 2002, last modified Oct 06 2004]

[link]






       Or could you utilize those big, chunky-treaded, mountain bike tires?
FarmerJohn, Oct 04 2002
  

       Or eat a lot more.... It's not like any of the damn fool bikers in Ann Arbor stop for a red light anyway.
Mr Burns, Oct 04 2002
  

       Alternatively, have your S.O., or hire someone, to drive in front of you in a car, pace car style.   

       Another alternative is to have a gun that, first, inflates beach ball sized spheres covered in radar reflective paint and second, fires them forward at speeds above the detection threshold.   

       Yet another possibility is to have a radio-controlled drone flying above you. It would have to be sophisticated enough that it could loiter ahead of your position and then swoop at the radar transceivers at the right time. Perhaps they are set to always maintain a 50 meters-in-advance position relative to yours.   

       Then there is the radar reflector on the catapult arm approach: a bicycle-mounted; spring, counterweight or bicycle-drivetrain energized; arm that is released and allowed to fly forward at super-threshold speed as you approach the light.   

       Of course, maybe just the addition of a freewheeling propellor to the bicycle would be provide enough of a speedy signature to trip the system.   

       Finally, an electronic device that transmits a falsified radar return at the radar transceivers, telling them that an object is approaching at super-threshold speed, whatever that is. In essence, a jammer.
bristolz, Oct 04 2002
  

       The really cool thing about this is you can experiment with radar for almost free - you have your bike and the city provided the radar. Your idea about the cubes makes sense - I think angular surfaces are very radar reflective. Drink a case of beer, crumple the cans into balls, glue them together (hot glue) and mount this on a broomstick. It should be very radar reflective and appear huge to the robot. As you go to the light, thrust the Radar Beer Wand forcefully in the direction of the light. The combined velocity of bike and wand should be >30mph. Possibly the wand velocity alone could be 30mph. Coolest of all would be if you could change the light while standing still near the intersection, with only a wave of the RBW. You may need to convert the RBW into a mace-and-chain type apparatus to achieve the needed velocity of the reflective ball. I am envious of the awesome party you will have - beer drinking and tool construction followed by science. Start drinking. Report back monday. Good luck.
bungston, Oct 04 2002
  

       // There is a set of traffic lights on my way to work which is controlled by microwave doppler radar detectors (the little camera-like boxes atop the pillars). //   

       I've never heard of these. The camera-like boxes you refer to, to my knowledge, are for detecting emergency vehicle traffic and can change the lights to allow them through.   

       Sensor controlled lights are generally triggered by in-ground induction coils.
waugsqueke, Oct 04 2002
  

       [Waugs] I assume you are tawkin' about the strobe-light controlled optical sensors on traffic lights? They don't look much like boxes to me so I thought maybe [shameless] was describing systems like are used in some parts of Europe that do use radar controlled traffic light management.
bristolz, Oct 04 2002
  

       [Waugs] Yes induction loops are widespread but I think more for large centrally-planned integrated systems- Edinburgh is too wee and chaotic to have one of those. Though I suppose you could spoof them too- maybe with a passive coil of copper wire wound around the frame? Any actively emitting system might fall foul of our strict radio laws....   

       Aha! Maybe that would add some marketable "urban rebel" chic- plug in your MP3 player (or a pair of Technics) and you have your own mobile low-power pirate radio station. This should transmit on the local easy-listening frequency so you can pull up in a traffice queue wearing your "Naomi Klein" branded smogfiltering bandana and fracture car drivers' smug serenity with a blast of Japanese noise metal! Grrrr!
shameless_self_reference, Oct 05 2002
  

       I've never heard of the radar-dopplered stuff, as far as I know only induction loops are used in Australia. We have loops set up for cars -and- bicycles (but not both together). Generally the induction loops are only noticeable in effect during periods where the side road traffic is likely to be low (ie. at night). During the rest of the time the traffic lights are on a complex city-wide semi-synchronised system called SCATS (Sydney Co-ordinated Adaptive Traffic System). Note I'm not saying this is the system used elsewhere in the world. It is however used in parts of the US and Ireland.   

       If you come up to a set of traffic lights with induction loop at night, and it seems to be taking forever to change, try rocking your car back and forth a little without crossing the holding line (I usually move forward a tiny bit at a time, though never when there's other traffic). An induction loop works by picking up moving metal. We also use it in Permanent Count Stations along the highways, so we have some idea of the amount of traffic using them per day.
CrumbsDM, Oct 05 2002
  

       I presumed from the idea title that the proposal was to create a more readily timed bicycle, to thereby better enforce the use of bike lanes or speed limits for those lanes. I admire anyone I see with the appropriate attire in the act of using marked bike lanes; I'm appalled at anyone biking on the sidewalks for ‘healthy’ sport. Sadly enough, the latter use seems to predominate where I've lived for the last 15 years or so.
reensure, Oct 05 2002
  

       //a mace-and-chain type apparatus to achieve the needed velocity of the reflective ball//   

       bungston's balls on a stick, or bristolz' excellent suggestions, may be the solution. However, you might try the type of headbands with 2 long vertical springs on them that typically have a plastic star or heart at the end. Cover the heart or star with aluminum foil, and when you stop, the springs go "boing-boing-boing" (not certain of the technical term), at a high rate of speed. If this test works well, permanently mount the headspring system to your bike helmet, and enjoy newfound convenience in bicyclage.
Amos Kito, Oct 05 2002
  

       Stealth bike?
dare99, Oct 06 2002
  

       At first I thought I'd read 'Bicycle Radar Detectors.' "Do you know how fast you were going on that Schwinn?"
RayfordSteele, Oct 06 2002
  

       A more amusing variant on this is to equip yourself with a suitable backwave oscillator (travelling wave tube) in the 9.96 Ghz range, the sort of device installed in ECM pods on military aircraft - these pick up the incoming signal, apply a 60dB+ amplification, and re-emit it right down the axis of emission of the transmitter .... at short ranges, this has the charming effect of completely fusing the reciever (since most of these units are just a Gunn/Schottky diode combination and a mixer cavity, they've no effective protection against this).   

       Get a bigger alternator, though - these things pull a whack of current !   

       [EDIT] typo corrected, should have been 9.96 Ghz...
8th of 7, Oct 07 2002
  

       But that doesn't take into account the Schartz-Metterklume wave-guide resonance in restricted volumes problem, [8th]. This could be mitigated with Saki methods, though.
bristolz, Oct 07 2002
  

       Ho ho ho ....
8th of 7, Oct 07 2002
  

       . . . and a bottle of rum, even.
bristolz, Oct 07 2002
  

       In mitigation, all I did was drive the getaway van .....
8th of 7, Oct 08 2002
  

       can we build these reflectors into a jacket?
neilp, Jun 02 2006
  

       Laying your bike on it's side definitely works. The group I ride with does it regularly.   

       What I really want to solve though, is the increasing use of carbon-fibre and non- ferromagnetic materials in bikes that means they no longer interfere with the induction patterns the loops create, thus, not tripping the lights at all.
danpat, Jun 02 2006
  
      
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