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Comment by cyanbane | Hacker News Reader

I remember back in pre-internet days when BBS file directories were filed with ways to hack stop lights via pulses from a strobe light. Supposedly if you had the right pulse (and the cojones to have a pulsing strobe light on the front of your car) you could mimic the pulse in a siren and get reds to start a process immediately to switch to greens. Different locations had different pulse timings and people would find local ones and upload and aggregate them on some local phreaking BBS'.

Never tried this myself.

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That's right -- I knew them as "silver boxes." But apparently they were called "chrome boxes" in other circles: http://www.aboutphone.info/lib/phreak/boxes-2.html

Interesting times.

I love how hackers love giving things cute names. These days everything has an actual term: they're preemption devices. http://prioritygreen.com/index.htm

Always thought that was an urban legend. I'm not from the US, however in New Zealand the lights would never change as an ambulance/police car went past. They'd just slow down as everyone moved out of their way.

Have witnessed this also for our Prime Minister driving past with a convoy of police and black SUV's.

In the US, these are certainly real. Apparently, some did use strobe lights to signal the traffic lights.

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

I vaguely have memories of the state legislator having to pass new laws after the devices were installed because it was not technically illegal to have the emitter in your vehicle.

Usually only certain traffic signals are equipped with the detectors, but they do in fact use strobe lights to trigger the light switch and it does happen immediately. It doesn't work with any emergency lights, though -- a separate, specific strobe light be must installed to trigger the signal.

Just across the pond in Sydney, Australia, one of my earliest jobs was related to the traffic control systems at the Roads and Transit Authority (RTA). I do have the distinct impression that they had wireless communications allowing reprogramming of lights by emergency service vehicles. They also had zero authentication ISDN-based video dialups on major intersections, under-road sensor loops to compile traffic volumes, and had kept a VAX running right through to ~2001 and later. Most of that's probably gone now, but I suppose the wireless traffic manipulation is still about.

Was it the SCATS system by chance? http://www.scats.com.au/

Yep. SCATS is the name of the base system, very successfully exported to many countries overseas, some of which became our later customers. We were focused on third-party provision of complementary products.

I used to try to mimic this by flashing my high beams at them. I don't know if it worked but it sure seemed like it did at least some times.

Randomness will do that.

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