Traffic light control

This is the place for any magazine-related discussions that don't fit in any of the column discussion boards below.
Post Reply
User avatar
moe
Posts: 80
Joined: Fri Jan 11, 2002 1:01 am
Location: USA
Contact:

Traffic light control

Post by moe » Sun Dec 15, 2002 9:28 am

Can anyone tell me how a traffic light control works? In town they changed the lights so when a emergeny fire or police car pass with there lights on they get the right of way . Is there a rate ,frequency or cycle that the light strobe flashes? a tow truk went by with it's strobe lights on and the lights did not change.Thanks for any help.

User avatar
Chris Smith
Posts: 4325
Joined: Tue Dec 04, 2001 1:01 am
Location: Bieber Ca.

Re: Traffic light control

Post by Chris Smith » Sun Dec 15, 2002 9:59 am

A small device atop the light pole that looks like a small camera sets it off to change the lights in favor of the emergency vehicle. <p>Sound, light, or radio waves encoded do the trick. <p>Each city may use different means, but all three methods are supposed to be uniform?

Dean Huster
Posts: 1263
Joined: Wed Dec 05, 2001 1:01 am
Location: Harviell, MO (Poplar Bluff area)
Contact:

Re: Traffic light control

Post by Dean Huster » Sun Dec 15, 2002 8:24 pm

The ones I've seen are triggered by a low-power radio signal on the emergency vehicles and bring the entire intersection to a full red-light-on-all-the-time stop in all directions, rather than in favor of the emergency vehicle. This allows the emergency vehicle safe access to the oncoming lanes for travel through the intersection. To do the latter would make for a very messy detection system and possibly wouldn't allow for some odd variations in traffic patterns through the intersection.<p>Dean
Dean Huster, Electronics Curmudgeon
Contributing Editor emeritus, "Q & A", of the former "Poptronics" magazine (formerly "Popular Electronics" and "Electronics Now" magazines).

R.I.P.

User avatar
dacflyer
Posts: 4538
Joined: Fri Feb 08, 2002 1:01 am
Location: USA / North Carolina / Fayetteville
Contact:

Re: Traffic light control

Post by dacflyer » Sun Jan 05, 2003 10:37 pm

i work in traffic signals here... its called pre-emption...some use a strobe flashing at a certain frequency, and kelvin color..almost impossible to homebrew...
also some use radio signals...depends on the city..most are all on different frequencys...and are trunked frequencys now
they are integrated with their 2 way radios<p>the ads you see in magazines.. don't work...lol
we have tested them...

User avatar
dacflyer
Posts: 4538
Joined: Fri Feb 08, 2002 1:01 am
Location: USA / North Carolina / Fayetteville
Contact:

Re: Traffic light control

Post by dacflyer » Sun Jan 05, 2003 10:39 pm

oh,, by the way...tow trucks are not considered emergency vehicles..only fire / rescue / ambulance
are..

Post Reply

Who is online

Users browsing this forum: Google [Bot] and 42 guests