Is there a radio frequency receiver on traffic lights??

[Robert Gift]

With a radio signal, the traffic light could not know from which direction the EV is coming and therefore which direction to give a green signal.

Or does the green phase cycle to red so all directions are red.

Another problem is that other traffic signals within range would likewise be affected.

I suspect it only allows the signal to be monitored and readjusted remotely.

[Siren Man]

my friend is an EMT. hes showed me before. trust me thats what they are for.

[zetronist]

my friend is an EMT. hes showed me before. trust me thats what they are for.

There are some systems that use RF activation for traffic signal pre-emption. However, they do not use Yagi beams; you'll find a simple 1/4 wave UHF antenna on a box, usually on the control panel. In some systems, the antenna is not even visible. Some of the systems involve a voting system, with multiple antennas and a computer that can instantly tell which direction the unit is coming from.

Such systems are extremely expensive, though I have seen them marketed in JEMS and FIRE COMMAND.

Most traffic light pre-emption today is optical, like 3M's Opticom System, which not only changes the lights, but records a unit identifier so there is an official record of the preemption. As Robert has pointed out, optical preemption is the way to go in terms of locating the vehicle. The Opticom system also has a safety feature on it. If two emergency vehicles come from opposing directions, the first one to capture gets the "green". What that means is if your Opticom is on, and the light does not change for you, STOP-- another emergency vehicle is entering the intersection at the same time or slightly before you.

I've used the Opticom system in EMS for over 10 years now, and it works quite well. Having worked as a paramedic in Camden County, NJ, New York City and Suffolk County, NY for the past 30 years, I've seen a lot of systems. Opticom, in my opinion, is the best.

There are multiple uses for transceivers attached to traffic controls and hence their various types of antennas. As I mentioned in my earlier post, the majority of time, at least in NY, when there is a Yagi beam, it's pointed at the next light down (or up) the road.

John.

[Jim_Ferer]

With the right antenna and a low-powered signal the "too many lights" syndrome could be mostly avoided. If the cycling went a block too far it's not the end of the world.

[Robert Gift]

Thanks for the education, John.

Never imagined anyone would go to the trouble of discerning radio signal origin.
I would think RF signal reflection would also be a problem, and traffic signals at other blocks on both sides of the EV route would be affected.

I like Opticom except in heavy snow. In snow the reflection was very interesting, and I wondered if it could cause optically-induced seizures.
I also liked that the strobe emitters acted as an additional emergency light.

[Elliott]

With most of the systems in Cincinnati that I have seen, they ALL turn red, and a white floodlight (or blue beacon in Sharonville)flashes to let EV's know they have right-of-way. With all red, it could be done omnidirectionally.

[Robert Gift]

Does that work well?

Giving EV a green through-signal and <-- left turn arrow (where one exists) allows vehicles ahead to proceed and clear an intersection so they are not blocking the EV approaching from behind.

This can be very helpful when the EV could be trapped beside uncrossable medians, or when opposing traffic is backed up preventing the EV from going left to pass backed-up traffic ahead.

Also, it at least helps move some traffic, whereas, all red stops progress of all traffic.

That is why I like 3M's Opticom better.

[zetronist]

Speaking of Ohio,

When I lived in Zanesville, Ohio (1984-1985) the Fire Department had the ability to turn all of the lights downtown on "Flash" (Red E/W and Yellow N/S) in the ENTIRE CITY all at once. There had to be over a dozen lights that would flash.

This was done with a circuit at Fire Headquarters and not by RF or optical means. The flashing cycle was on a timer. I remember it used to totally mess up the traffic, especially durning the rush hour! I believe that they did this for years before the more advanced systems came into being.

The good thing for buffs like me, was that you knew there was a fire and that you were about to hear the apparatus leave the station.

They probably don't do this anymore, but it was one of the hallmarks of that city for many years.

John

[Robert Gift]

Interesting!

But Opticom came out in the early 70's if not a little earlier.
But it is awfully expensive, both for each signal equiped and the EV emitters.

Even Opticom ruins rush hour traffic synchronization.
Vehicles denied their green signal cause other vehicles arriving behind to stack up. The green signal periods may be insufficent to allow all vehicles to get through. So back-ups continue throughout the entire rushhour.

[StonedChipmunk]

I read somewhere that there is a new company that is marketing a new add-on to the Opticom system. They use a transmitter and reciever module that, when a vehicle reaches the intersection, it is "asked" a series of tests from the traffic signal module, and if the transmitter sends back the correct responses the preemption system will be invoked.
The best thing about this system is that everything - and I mean EVERYTHING - is sent back to a base server to be logged. Direction, pass/fail, vehicle ID number, time and date, status of emergency lights/sirens on the vehicles... everything. All traffic lights can be controlled and the entire preemption system can be turned on and off, plus you can go into Lockdown mode which totally disallows any preemption access.
I checked my laptop for the PDF file and it says the product name is eLock and it's produced by Tomar Electronics. Quite interesting, as there has been people with simple strobe lights with filters on them gain access to preemption systems.