# (OT) Traffic Speed Detecting Signs

Our town recently got one of those Traffic Speed Detecting Signs, that tell you how fast you're going. I've always wondered how they work, and why they dont detect cars going the opposite direction.(I assume they work on radar). I also noticed that they only have TWO digits. Therefore, if you exceed 99mph, what does the sign do?
Last night I was in a convenvience store, when one of the local cops walked in. That was my chance to ask him what happens if someone exceeds 99mph. His reply was "I'll give you a speeding ticket". I laughed and said "that's what I thought you'd say". Then I said, "besides the ticket, what would the sign do?" He said he never tried it, so he dont know.
If a cop dont know, who does? I'm wondering if they go back to zero, or just keep showing 99?????
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
On Wednesday, August 10, 2016 at 4:11:00 AM UTC-4, snipped-for-privacy@unlisted.moo wrote:

Obviously your town doesn't have a Idiot Ordinance. If they did, the cops would have arrested you on the spot.
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>

+10 and bet the cop had a good laugh later telling his fellow cops about the idiot at the store
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
ChairMan wrote :

He was probably at the 99 cent store trying to hand the clerk a dollar just to see what would happen.
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
On 08/10/2016 07:44 AM, ChairMan wrote:

Dudes! This is not a stupid question. This is a fun question. When did you guys lose your sense of curiosity?
My guess is that the display is driven by a BCD (binary coded decimal) counter and that it just rolls over to 00.
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>

I know this cop and he's a decent guy. I think I caught him off guard with this question, but he was having a little fun with it, as well as I was. But it really is a question which has an answer (somewhere). I assume those signs have user manuals, and there must be a mention of using them for speeds over 99. Normal drivers wont experience that speed, but if those same signs were used at a race track, they would not work, since many race cars exceed 99mph. Since truck and tractor pulls uses these signs, I would think that race tracks would use a similar device, but obviously need one that allows for 3 digits. (I assume they make a 3 digit one for such uses).
I wish I knew the manufacturer of the sign, so i could see if there is a user manual online.....
Till then, I'll go along with the "roll over to 00" !!!
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
On 08/11/2016 01:02 PM, snipped-for-privacy@unlisted.moo wrote:

It is a good sign that your felt you could approach him. It is a sign of a healthy police department. Community policing is the way it is suppose to work.
:-)
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
It happens that snipped-for-privacy@unlisted.moo formulated :

Two and a 'half' digits would be good enough for displaying speeds up to 199 MPH. It cuts down on the circuitry needed in the display.

I would think of it as a two and a half digit display with the 'half' being left to the reader. It could well be that a log could be kept which logged speeds well above 100 MPH rather than a rolling over, leaving only the display limited to two digits.
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>

K-band single directional radar unit Latest generation AlInGaP high intensity LED’s 12” or 18” Full Matrix (rounded) Characters for quick recognition Minimum Speed Display, High Speed Blanking & Flashing Digit Violator Alert Automatic intensity adjustment to ambient light conditions 12 VDC operation, 12 VDC or 100-277 VAC, 50/60 Hz input Power consumption: 5.76W Nominal, 14.88W Peak Keyed On/O switch Single cycle ON/OFF clock Sign defaults to last settings upon power up Built in on-screen diagnostics On-board Options & Diagnostics Radar sensitivity LED Operation Diagnostics LED Intensity Diagnostics MPH / KPH operation Battery test And more...
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
On 08/11/2016 07:33 PM, FromTheRafters wrote:
[snip]

I used to have digital thermometer that had 2.5 digits, which was enough since the thermometer couldn't handle temperatures above 140 degrees.

100+ could be indicated by the display flashing. Flashing "00" if anyone managed to drive 200.
--
Mark Lloyd
http://notstupid.us/
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Mark Lloyd used his keyboard to write :

True enough. My point was that the counter wouldn't have to roll over just because of the limits of the display.
You can display Pi on a calculator and only get so many decimal places, yet you can then subtract 3.14159 from it and retrieve six more decimal places in many cases. The limits of the display does not necessarily limit the underlying calculation (or, in this case, the count).
Only by looking at the circuit or code used could I determine if the thing actually counts modulo 100 (0 through 99 and 'rolling over' dropping anything over 100) or just not displaying the most significant digit.
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
On Friday, August 12, 2016 at 2:56:20 PM UTC-4, FromTheRafters wrote:

Here's the code that should be used:
Dim driver_spd as Single Dim road_spikes as Boolean 'Speed Check If driver_spd > 99 Then road_spikes = True
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
DerbyDad03 posted for all of us...

Good one
--
Tekkie

<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
On Wed, 10 Aug 2016 03:09:05 -0400, snipped-for-privacy@unlisted.moo wrote:

That was probably a wrong answer too. At that speed you'd probably be arrested and charged with a series of reckless endangerment type charges. In CT if you are more than 20 over, off to the pokey.
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
On 8/10/2016 3:09 AM, snipped-for-privacy@unlisted.moo wrote:

He's mixing the sign and physical presence of cop. There are a couple of signs I frequently go through here and they blink off when your car has passed. They do not keep a record of your car and speed.
In Europe over 25 years ago we were told that trucks were required to have a recorded record of their trip and when cops pulled them over would check the record and could give them a speeding ticket even though they exceeded the speed hours ago.
One day with gps's and computers recording they could do this to anybody.
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>

That's the best kind.

<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>

I rarely see a cop near those signs. I know they signal is not being sent to the cops, recorded, or anything. The sign is programmed to flash if I'm exceeding the speed by more than 3mph or something like that. In town the speed limit is 20, and it wont flash at 21 or 22, but I think it starts to flash at 23 or 24 (and up).
Ive seen those same signs used at tractor and truck pulls to record the speed of the puller....
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>

The infamous "tachograph"
OBD2 computers on today's cars can apparently be queried to determine speed and whether the brakes were applied in accident investigation. Only the last few seconds are apparently available.
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>

Only if you have a car with gps and computers.
--
-----------------------------------------------------------------------------
Roger Blake (Posts from Google Groups killfiled due to excess spam.)
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
On Wed, 10 Aug 2016 03:09:05 -0400, snipped-for-privacy@unlisted.moo wrote:

Yes, they work on radar. Cars going the opposite direction DO get detected, but they show up as going a negative speed. The built-in software just ignores those signals and displays only positive speeds.
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>

## Site Timeline

• ### need tips/help for a rookie.

• - next thread in Home Repair
• ### Kitchen trash compactor hums when foot pedal is lifted

• - previous thread in Home Repair

• ### Re: time to ban electrial tape and flare.

• - last updated thread in Home Repair
• ### OT: I notice the brexshiteers haven't commented on JLRs reduction in production.

• Share To

HomeOwnersHub.com is a website for homeowners and building and maintenance pros. It is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.