Stoplights

[Scott73]

This is kind of radio related. What frequency do the devices that change the traffic lights green for emergency vehicles?. With software radios I would think one could build one with the correct frequency and change the lights. It's a fascinating system and it would be nice to be able to change the light especially when stuck in traffic. Is there a tone or DTMF that's transmitted to switch them or is it some super secret technology.

 

[eorange]

I believe it's a modulated light signal.

 

[cavmedic]

Most traffic preemption devices in the US work on the flash rate of a specific strobe light on the emergency vehicle. More commly knows as the " Opticom"

 

[W9WSS]

The traffic light pre-emption devices (at least in the Chicago area) are controlled by strobe lights that flash at certain times a second. The original devices were called "Opti-Com," but that is a 3M company's trade name. There are also infrared activators, which you cannot see as they are invisible to the naked eye.

For a while, Bolingbrook used RF devices that set the traffic control devices to green for emergency vehicles. I'm not sure if that technology is still in use or if they went to devices I first described.

 

[wtp]

and some of the lights i saw when driving years ago turned all the lights red.
that way the ones with the flashing lights and siren would only be the ones moving.
so, good luck turning the lights a different color, you might get your wish.

 

[mmckenna]

Many years ago in the city I grew up in, someone built their own Opitcom unit.
The PD eventually caught up with him, and there is now a law on the books to encourage others not to do it.

It's a fantasy of many that commute.

 

[a417]

someone built their own Opitcom unit.

Why recreate a Radio Shack programmable remote control?

It's a fascinating system and it would be nice to be able to change the light especially when stuck in traffic.

Laws like this exist because people do dumb ****.

The (branded) Opticom's were sensitive to IR, so when we were building light bars & vehicle packages you could either use the white strobe/coded power supply controller (which had a large IR wavelength component) or the 'invisible' IR emitter. The invisible emitters (when installed into light cutouts on lightbars) invariably caused "that pre-emption light is out" because people wouldn't see it flashing, or they owned an iPhone and couldn't see it thru the camera app. The people in the know, or who had Android phones submitted less paperwork...ahh, memories.

There were also RF controlled systems for limited access that ran on a remote control, and a couple that were sensitive (with directional horns) to aural patterns of sirens. A local university had a 2 second 'YELP' trigger on faculty lots, for instance.

 

[Para078]

Aren't some of them siren controlled?

 

[12dbsinad]

This is kind of radio related. What frequency do the devices that change the traffic lights green for emergency vehicles?. With software radios I would think one could build one with the correct frequency and change the lights. It's a fascinating system and it would be nice to be able to change the light especially when stuck in traffic. Is there a tone or DTMF that's transmitted to switch them or is it some super secret technology.

It's not super secret. If you're a licensed ham, just tune your radio to 146.52 and tell the light to turn green. Remember to properly identify. Of course, you'll need to be nice about it so you don't PO the streetlight. Saying please goes a long way.

 

[GlobalNorth]

It has been done and it is a bookable offense in my State.

 

[cavmedic]

Aren't some of them siren controlled?

I’ve never seen any to my knowledge like that in PA although there are some gated communities around here that react to a siren to gain emergency access.

 

[WB9YBM]

This is kind of radio related. What frequency do the devices that change the traffic lights green for emergency vehicles?. With software radios I would think one could build one with the correct frequency and change the lights. It's a fascinating system and it would be nice to be able to change the light especially when stuck in traffic. Is there a tone or DTMF that's transmitted to switch them or is it some super secret technology.

Here in Illinois ay least (maybe other states as well) they're triggered from strobe lights on emergency vehicles. I'm not sure what kind of fines people get that install a strobe light in their car (or use a hand-held type), but as a minimum I've heard that they get confiscated by the PD unless you can show some kind of official authorization (i.e. badge, etc.) for having one in your car.

 

[im800mhz]

I'd go into your local PD and ask them how to build one.

 

[prcguy]

I've had a few 3M Opticom units over the years. They work very well and I have many stories I that I can't tell about using them.

 

[W9WSS]

It is a criminal violation in Illinois to have an intersection pre-emption device in one's possession unless they are an installer or a member of a team or municipal entity that installs the devices in emergency vehicles. And of course, the law enforcement officer, fire department/EMS driver who uses the device operating in the vehicle he or she is driving.

 

[chief21]

An interesting thread - and one that I can identify with.
A few years prior to my retirement, I was part of a committee charged with recommending which technology to employ for a county-wide preemption system. After many months of research, it eventually came down to two different systems... the mature technology that utilized optical emitters and detectors, versus a much newer, much more complex technology that utilized RF and GPS.
In a nutshell, the optical system required a simple emitter in each vehicle, as well as a preemption controller and multiple optical detectors for each intersection, while the RF system required a controller, GPS receiver and RF transmitter (and associated antennas) for each vehicle, as well as a controller, RF receiver and GPS receiver (and associated antennas) for each intersection. Special FCC licensing was also required.
I don't recall the actual cost difference, but the RF system was something more than twice as much as the optical system for the first corridor and a limited number of vehicles.
I found it interesting that although the RF system was much more expensive and much more complex, with multiple potential points of failure, the committee voted to recommend it for implementation.
I retired and moved away just before the first phase of the system was due to be installed. That was over 15 years ago. I wonder if that RF system is still in use?

 

[littona]

Take a look at gtt.com... looks like the cool kids are now using a mix of IR and RF solutions.

 

[WB9YBM]

I'd go into your local PD and ask them how to build one.

They used to sell strobe lights at Radio Shack; I think at least some party stores still have them. Yes, schematics are most likely on the Internet somewhere too but a cautionary note: the blubs required in strobe lights operate with some seriously high voltage that's dangerous if not treated with utmost caution.

 

[merlin]

That is called opticom, a repetitive pulse (strobe) of light. each strobe has a strobe like a coded light signal that compares to remote control. Sad part is because people were using home made strobes for this, cities have changed the lights to 4 way red. Want to make one, the flash from a camera works well. All sorts of DIY strobe circuits online.
Yea, get caught preemting a traffic signal you loose your goodies at minimum, some cities may have fines over that.

 

[WB9YBM]

Now if only we could get more people to get out of the way when an emergency vehicle comes down the road with lights flashing! (It's amazing what people forget once they pass diver's ed.)