False Radar

[imouttahere]

Not sure where to post this but I'll try here first. We were stopped by a radar police unit that said we were doing 72 mph. We have a Ford 550 with a 38' Mobile Suites. We came over the top of a hill and started down the other side. The speedometer registered 58 at the top as we started down. I braked to reduce the speed to the 55 mph speed limit. I noticed the cop down at the bottom of the hill. I kept the speedometer pegged at 55 the whole way down the hill. As we passed the cop he lit up the lights & pulled us over. Said we were doing 72 at the top of the hill and slowed down to 69. Imagine how frustrating it is when you know you were doing the limit & get pulled over. We confirmed afterwards with a gps unit that traveling at 55 mph we were actually doing 55.

A few miles down the road, there was some construction and they had one of those mobile radar units that light up & tell you what your speed is. As we approached at 53 mph, it flashed 55 & immediately changed to 72 mph & stayed at that speed indication as we passed it. Again we checked the gps & it also indicated we were doing 53.

The question I have is what the heck is causing the false radar indications? I have no radar detector and the only other thing I can think of is the tire pressure monitor that is wireless. We also have two iphones.

Something is causing the radar to indicate that we are doing about 14 to 15 mph faster than we really are. I can't keep getting a ticket at every radar trap in the country. HELP MR. WIZARD

[Scooter]

Well, if it is not too late....you can challenge the ticket. If not now, the next time.....get the model and serial number of the officer's radar gun. Contact the supervisor and find out when it was last calibrated. Perhaps the gun is way off.

This will be a big hassle as you might have to go back to court, get records, etc.

[Ray,IN]

Since two different types of radar equipment both gave a reading of 72, it makes something about your rig suspect. Determining exactly what will likely be quite difficult. It would take a good attorney to contest and win against police radar readings. Were it me, I would visit my local law enforcement, explain what happened in both instances, and ask to be scanned by radar with a LEO in the truck with me. Of course this could backfire.

[RickO]

Originally Posted by Ray,IN

. Of course this could backfire.

What could go wrong Ray?

Rick

[jamvir]

Originally Posted by Ray,IN

Since two different types of radar equipment both gave a reading of 72, it makes something about your rig suspect. Determining exactly what will likely be quite difficult. It would take a good attorney to contest and win against police radar readings. Were it me, I would visit my local law enforcement, explain what happened in both instances, and ask to be scanned by radar with a LEO in the truck with me. Of course this could backfire.

I would modify this slightly - have a LEO follow you to check the accuracy of your speedometer, while another is using a stationary radar. I suspect your speedo is incorrect. Nothing on your tv or 5er should cause a radar unit to read incorrectly.

Jim

[mwells4654]

I do not think the speedo is incorrect if the GPS is also stating the same speed. I think having a LEO use a stationary radar is the best bet. I have an old 84 truck and saw a LEO on the side of the road. Told him I thought my speedo was off and he was more than happy to check me multiple times as I drove by. Speedo was off and varied by how much by how fast I was going. At 45 I was doing 50 and at 55 I was doing 65. At 65 I was doing 80+. Glad he helped me out.

[jsteinberg48]

Did you change wheel diameter and tire size?

[Bruce C]

I think most law enforcement would be willing to help if you thought you had an issue with your speedometer.

[1010]

Originally Posted by imouttahere

Not sure where to post this but I'll try here first. We were stopped by a radar police unit that said we were doing 72 mph. We have a Ford 550 with a 38' Mobile Suites. We came over the top of a hill and started down the other side. The speedometer registered 58 at the top as we started down. I braked to reduce the speed to the 55 mph speed limit. I noticed the cop down at the bottom of the hill. I kept the speedometer pegged at 55 the whole way down the hill. As we passed the cop he lit up the lights & pulled us over. Said we were doing 72 at the top of the hill and slowed down to 69. Imagine how frustrating it is when you know you were doing the limit & get pulled over. We confirmed afterwards with a gps unit that traveling at 55 mph we were actually doing 55.

A few miles down the road, there was some construction and they had one of those mobile radar units that light up & tell you what your speed is. As we approached at 53 mph, it flashed 55 & immediately changed to 72 mph & stayed at that speed indication as we passed it. Again we checked the gps & it also indicated we were doing 53.

The question I have is what the heck is causing the false radar indications? I have no radar detector and the only other thing I can think of is the tire pressure monitor that is wireless. We also have two iphones.

Something is causing the radar to indicate that we are doing about 14 to 15 mph faster than we really are. I can't keep getting a ticket at every radar trap in the country. HELP MR. WIZARD

I spent over 30 years in traffic law enforcement and thankfully retired before the agency I worked for began forcing the use of radar on us. Unfortunately there is a big difference in the use of and training requirements in law enforcement, especially when it comes to traffic enforcement. I can not speak for any other state other then the one I worked for, but at a minimum the officer using the radar should have calibrated the unit prior to the beginning of the shift (or being used) and at the end of the shift. The calibrations should be noted. If the proper methods of calibration were used and noted this would stand up in court. The radar used on the side of the road for warnings may be accurate (most seem pretty darn accurate based on the consistency of my speedometer readings) but they would be held to the same standard as the radar used by the police if introduced as evidence. Your GPS would be held to the same standard too. Nothing in your vehicle would cause a false reading of the radar. Again, not sure on department policies where you were, but in todays climate of liability no officer would be allowed to "pace" your vehicle or test the accuracy of your speedometer with an officer inside your vehicle or by using dept. radar. Based on what you have said, the difference of what the "radar" read and what your speedometer read was 14 mph at the top and bottom of the hill, rather consistent. I would suggest you have the speedometer of your vehicle calibrated at a certified shop and then you will know if your speedometer reading is your actual speed. There can be a number of reasons why the speedometer is off, one common reason is putting on larger tires, but 14 off is a bit high, so it could be an electronic or mechanical problem. In Ca. you are not required to have a speedometer, but you are required to go the sped limit. If a person makes the effort to calibrate the speedometer, repair the speedometer if needed and present the paperwork to the court, it might be dismissed. If you present a calibrated certificate showing the speedometer was accurate to the court, then the use of the radar (calibration or officer) would be suspect and you may be found not guilty. Any way you go, calibrate the speedometer.

[dagray]

In California the Officer would have to testify to the fact that he observed you traveling faster than was safe and verify that speed with the radar. If one uses a radar unit any time at all, they can visually determine your speed within a couple miles per hour. His experience and the size of your rig may be a factor.

Was he using a doppler radar or a laser radar?

[azdryheat]

Laser radar? No such animal.

[pagosajoe]

Originally Posted by azdryheat

Laser radar? No such animal.

Sure is...
Police Laser Radar

[Brockx]

I would check your speed manually using interstate markers. Drive an indicated 60mph, verify speedo by GPS.
At 60 mph you should do a mile marker every 60 seconds, every second you are off, plus or minus, is one mph. Do several because the markers could vary a little, use only the mile markers not interchange numbers. If your speedo is correct talk a cop into radaring you, something is weird, keep us posted.

Edit
59 sec = 61mph
61 sec = 59mph etc etc

[DonDee]

Originally Posted by jsteinberg48

Did you change wheel diameter and tire size?

" We confirmed afterwards with a gps unit that traveling at 55 mph we were actually doing 55."