Construction Site Speed Monitors

[Rancher_Will]

This is a question that has been in my mind for years. I wonder if others have noticed it.

I regularly drive, with and without our RV 5th Wheel RV, in locations where special speed signs, perhaps radar reading, post the speed that each vehicle is moving at the site. Such signs at school crossings, construction sites, etc., are common. These signs usually follow warning signs that speed is restricted ahead.

In our area all of the local speed signs, such as school area or school crossing signs, or other such signs, register almost exactly the speed that I am moving when they show the speed and changing speed. So I know that my speedometer(s) must be accurate.

However, I have noticed that on the Interstate Highways, the speed signs at construction sites almost always read about 5 MPH faster than my speedometer reading in my vehicle as I approach and pass the sign.

Has anyone else noticed this too? I often think it the sign is set on purpose so that traffic will slow down even slower than the posted speed limit at those sites.

[philh]

I've never noticed them being off...

My employer (large multi national company) has a complex that's about a square mile with city streets running through the complex. Security posted those silly radar units. they finally realized it was a competition to who could get the highest speed and removed them.

[petendoll]

I have noticed this also. I thought my speedometer was off.

[Matt_Colie]

We encountered way too many of those during our most recent excursion. And, by my memory, they all agreed with my GPS. The speedo still reads a little low, but not enough to matter.

Matt

[D_E_Bishop]

Long before the speed signs of today, Sam Taylor the first Engineer to head the Los Angeles Dept. of Transportation had us build one for him that we had to manually move the speedometer needle on the sign. I say manually, we actually used the controller and servos from a remote controlled model airplane. We used a radar gun to determine the vehicle's speed and then adjusted the needle for the drivers to see. We had to adjust the radar gun everytime we used it. It was LAPD issue.

[Cloud_Dancer]

I trust my speedometer. I do what I can in order to not get a speeding ticket.
Those large speedometers on the side of the road are good reminders,.....regarding the importance of speed control.

[2012Coleman]

gbopp wrote:
On a similar note, I've noticed when I go to a doctors office and get weighed, I'm always 5 pounds heavier than at home.
I have a couple scales at home and they're all within a pound.
But, it seems all the doctors office scales show 5 pounds more.

Maybe, it's for the same reason construction radar shows you're going faster?

You more than likely have more clothes/shoes on at the doctors office.

[portscanner]

[valhalla360]

I've found most car speedos read high compared to GPS speed. I suspect it's to protect the car companies if you get a ticket. You can't blame it on the speedo.

In principal, the radar units should be dead on but they do need occasional calibration. I'm in the industry and never heard of a systematic manipulation of the radar signs. Doesn't mean some yahoo hasn't decided to do it but it goes against sound traffic engineering principals, where we want the motoring public to trust the information we provide.

[cmeade]

wa8yxm wrote:
I suspect the signs (fixed) in school zones and such are calibrated by the police from time to time and much better maintained than the portable construction zone signs.. There is also the chance it's not reading your ride on a freeway but someone else, possible a vehicle on the other side of the divided highway.

As for the doctor's scale someone mentioend.. I use a beam balance here at "home" and weigh myself in near "Shower" dress In the DR's office my shoews alone add a few pounds. and the Trowsers and such, all adds tonnage.

Not to mention your 2 rolls of quarters rolled up in a sock, your gun and 15 inch Bowie knife hanging from a neck scabbard!!!! LOL.

[wa8yxm]

I suspect the signs (fixed) in school zones and such are calibrated by the police from time to time and much better maintained than the portable construction zone signs.. There is also the chance it's not reading your ride on a freeway but someone else, possible a vehicle on the other side of the divided highway.

As for the doctor's scale someone mentioend.. I use a beam balance here at "home" and weigh myself in near "Shower" dress In the DR's office my shoews alone add a few pounds. and the Trowsers and such, all adds tonnage.

[Homer1]

It would seem reasonable to set the highway speed signs a little higher than actual. People are caught up in the rush of traffic, they are in a frenzy of doing the max + 5mph. I would do the same thing.

[korbe]

As soon as I see the mph sign, I peak at my dash. Always a bit lower than my actual speed. I see it as a way to slow us down, but I sure don't use that sign as a way to see if my gauges are working properly. And I never use it to slow me down......

[gbopp]

On a similar note, I've noticed when I go to a doctors office and get weighed, I'm always 5 pounds heavier than at home.
I have a couple scales at home and they're all within a pound.
But, it seems all the doctors office scales show 5 pounds more.

Maybe, it's for the same reason construction radar shows you're going faster?

[OkSixpack]

It's probably because most people go 5mph over the posted speed limit.
Jim