Re: Ambulance pre-emptive traffic light capability?



On Apr 22, 5:34 pm, Paul S Wolf <paul.s.wolf...@xxxxxxxxxxxxx> wrote:
On 4/22/2009 12:57 PM, richard wrote:

On Tue, 21 Apr 2009 20:34:49 -0500, "Richard Carlson, N9JIG"
<use...@xxxxxxxxxx> wrote:

In article
<98369c4c-e4b1-4172-b7f6-eb670c367...@xxxxxxxxxxxxxxxxxxxxxxxxxxx>,
hanco...@xxxxxxxxxxxx wrote:

Do ambulances and other emergency vehicles have the ability to pre-
empt traffic lights?

I was at an intersection and an ambulance (lights/siren NOT on) came
along and stopped for the red light.  A strobe mounted on the top
front blinked and the other signal changed to red.  But, the existing
red did not drop down to green, that is, all sides showed red.  The
ambulance then went through.

Many years ago when there was an emergency in Atlantic City NJ all
traffic lights (which were coordinated along the main drags) went to
blinking yellow; but I assume that was done manually.  (I wonder if
that's still done or has been discontinued).
Traffic Preemption devices (Often called OptiComs) are common around the
USA. Almost every suburb of Chicago has them and I have seen them in
many areas around the country.

They are basically a receiver connected to traffic signals, usually with
a notifier light. Around here they are set up usually with either
infrared or light strobes. The notifier light is usually a bright white
or lunar colored light. If the notifier is flashing then the emergency
vehicle is on your street, if it is steady then it is on the cross
street.

Some drivers have purchased or stolen emitters (IR or strobes) to
activate OptiComs so they can pass thru intersections, this is illegal
of course, but it still happens from time to time.

When these first were installed around here in the 1970's we found that
the original versions could be fooled with a bright spotlight flashed or
waved appropriately. Newer systems require a more precise timing or
coded IR.

Our area has receivers that work on both IR and strobes, and our FD's
and many police cars have one or the other.

The Wiki article athttp://en.wikipedia.org/wiki/Opticom_Systemis
pretty accurate and can fill you in on some of the rest of the details..

http://www.youtube.com/watch?v=CGD6gYlPaaY

Is this what you are talking about?
Watch the red light and you'll see a white strobe.
Or is it something else?

No.  That's a strobe built in to the red light for emphasis, and is not
permitted by the MUTCD.

Here's an example in Eastlake Ohio:

http://maps.google.com/maps?f=q&source=s_q&hl=en&geocode=&q=eastlake+...


Out of curiosity, why are the strobes not permitted?

I think they are pretty effective.

On another subject, OH is finally using metal supports for signals.

Welcome to the 21st c.

Just kidding there were a few around in the 70's.



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