# Got a Ticket, Need Info on Speed/Radar Laws & Out of State Stuff **URL:** \ **Category:** Miscellaneous and Personal Stuff I Must Share\ **Created:** [November 28, 2003, 6:55am UTC](https://boards.straightdope.com/t/got-a-ticket-need-info-on-speed-radar-laws-out-of-state-stuff/215691 "2003-11-28T06:55:40Z")\ **Posts on this page:** 8\ **Page:** 2
**Author:** ![BrotherCadfael](https://avatars.discourse-cdn.com/v4/letter/b/977dab/32.png) [@BrotherCadfael](https://boards.straightdope.com/u/BrotherCadfael)\ **Post date:** [November 30, 2003, 12:31pm UTC](https://boards.straightdope.com/t/got-a-ticket-need-info-on-speed-radar-laws-out-of-state-stuff/215691/21 "2003-11-30T12:31:26Z")
I should add that this is what I have been told by several police officers, and _not_ by attorneys specializing in this area. According to what I have heard, chances are pretty good that either, (1) they won’t bother putting on a full-blown jury trial for a simple traffic ticket, or (2) the ticketing officer won’t be able to show up on the day of the trial. Either way, you’re off the hook. But, if the trial is held, and the officer shows up to testify, you are about 99% certain to lose. ---
**Author:** ![zamboniracer](https://avatars.discourse-cdn.com/v4/letter/z/e9a140/32.png) [@zamboniracer](https://boards.straightdope.com/u/zamboniracer)\ **Post date:** [November 30, 2003, 11:36pm UTC](https://boards.straightdope.com/t/got-a-ticket-need-info-on-speed-radar-laws-out-of-state-stuff/215691/22 "2003-11-30T23:36:44Z")
> [@](#): > > \*Originally posted by BrotherCadfael \* > \*\*Ask the court for a jury trial. They probably (three out of four times or so) will just blow it off rather than go to all that trouble for a speeding ticket. > > If they go ahead with it, plead nolo and pay the fine. \*\* This isn’t good advice in most cases because one isn’t entitled to a jury trial on traffic tickets. ---
**Author:** ![Earthling](https://avatars.discourse-cdn.com/v4/letter/e/90db22/32.png) [@Earthling](https://boards.straightdope.com/u/Earthling)\ **Post date:** [November 30, 2003, 11:45pm UTC](https://boards.straightdope.com/t/got-a-ticket-need-info-on-speed-radar-laws-out-of-state-stuff/215691/23 "2003-11-30T23:45:12Z")
> [@](#): > > \*Originally posted by DaPearl \* > **Its not worth the time and effort to get a lawyer for one ticket.** Is taking a defensive driving class an option? ---
**Author:** ![Clothahump](https://avatars.discourse-cdn.com/v4/letter/c/51bf81/32.png) [@Clothahump](https://boards.straightdope.com/u/Clothahump)\ **Post date:** [December 1, 2003, 3:49am UTC](https://boards.straightdope.com/t/got-a-ticket-need-info-on-speed-radar-laws-out-of-state-stuff/215691/24 "2003-12-01T03:49:45Z")
> [@](#): > > \*Originally posted by Earthling \* > \*\*Is taking a defensive driving class an option? \*\* It is in Texas. You can burn one moving violation a year by sitting through a DD class. Dunno about the Northeast states and whether they do that or not. ---
**Author:** ![astro](https://avatars.discourse-cdn.com/v4/letter/a/9dc877/32.png) [@astro](https://boards.straightdope.com/u/astro)\ **Post date:** [December 1, 2003, 5:06am UTC](https://boards.straightdope.com/t/got-a-ticket-need-info-on-speed-radar-laws-out-of-state-stuff/215691/25 "2003-12-01T05:06:04Z")
> [@](#): > > \*Originally posted by Musicat \* > \*\ ***Badge,** now we’re talking physics here. Just how is the radar unit going to measure the speed of the host vehicle unless you’re suggesting it be pointed at a fixed object as well as the subject vehicle? And why would it, if there is a readily available speed data signal in the car already from the speedometer? > > A basic radar unit can only tell relative speed. If a car traveling at 20MPH is coming towards the radar unit, and the radar unit is travelling at 30MPH, the relative speed is 50MPH. To give an accurate value for the subject car only, it needs to subtract the speed of the cop’s vehicle. Not a problem if the cop has a speedometer. > > Also remember, radar (or any other signal bounce/sense concept) measures the time it takes for a pulse to be returned, and using simple mathematical calculations, displays the speed _of whatever it is pointing at_. And there’s the rub. If the beam is not pointed correctly, or is so wide that more than one vehicle is included, the measurements will not be reliable. > > So, **DaPearl** , this info might be useful, although in my experience, no reputable prosecutor would come to a court case without the “radar unit certification and calibration records” as **Badge** mentioned. Your request for them might still be useful; if the prosecutor checks them and sees they are old or out of tolerance, he may prefer to drop the case. Every little bit helps. \*\* Well… as badge indicated radar guns with this ability do exist (see below) and are not hooked to the police car speedometer. How the radar determines the relative speed of host vehicle I will leave to the SDMB engineers and pro-am gearheads to explain. [How police radar works](http://www.superiorcarcare.net/policeradar.html) > [@](#): > > Types of Radar Guns Two different types of radar guns can be used by police - parked and moving. Stationary radar guns must be used from a fixed position, like a police car on the side of a road. Moving radar guns have the added ability to target approaching or passing vehicles while an officer is driving on patrol. With the “same lane” setting that is featured on many of the newer moving radar models, police can even clock vehicles while driving up from behind, creating a growing need for rear facing radar detection for motorists ---
**Author:** ![astro](https://avatars.discourse-cdn.com/v4/letter/a/9dc877/32.png) [@astro](https://boards.straightdope.com/u/astro)\ **Post date:** [December 1, 2003, 5:13am UTC](https://boards.straightdope.com/t/got-a-ticket-need-info-on-speed-radar-laws-out-of-state-stuff/215691/26 "2003-12-01T05:13:08Z")
This site seems to suggest that the dual beam “moving mode” radar is using reflections off surrounding road objects to calculate the relative speed of the host car. [Appendix C. How radar works](http://www.magma.ca/~fyst/appndxc.htm) > [@](#): > > There is a variation of traffic radar, which is called moving radar. It works pretty much the same way as the type described above (stationary radar), only that moving radar is used when the cop car is moving (for the purpose of highway patrol, for example). There are two readouts on the radar unit, one shows the target speed, one shows the cop car speed. The strongest return signal, usually reflected from highway signs, bridges or other objects, is assumed to be the cop car speed. The next strongest signal, is assumed to be from the target. Since the target speed will only be relative to the cop car speed, therefore by adding the cop car speed to the relative target speed, one will get the absolute speed of the target. Moving radar is subject to all the errors stationary radar has, plus the error of determining the cop car speed. ---
**Author:** ![Angel\_of\_the\_Lord](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/angel_of_the_lord/32/2949_2.png) [@Angel\_of\_the\_Lord](https://boards.straightdope.com/u/Angel_of_the_Lord)\ **Post date:** [December 1, 2003, 5:18am UTC](https://boards.straightdope.com/t/got-a-ticket-need-info-on-speed-radar-laws-out-of-state-stuff/215691/27 "2003-12-01T05:18:36Z")
Er, **DaPearl** , maybe I missed this in your posts, but. . ._were_ you speeding? 😕 ---
**Author:** ![Musicat](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/musicat/32/20189_2.png) [@Musicat](https://boards.straightdope.com/u/Musicat)\ **Post date:** [December 1, 2003, 6:38am UTC](https://boards.straightdope.com/t/got-a-ticket-need-info-on-speed-radar-laws-out-of-state-stuff/215691/28 "2003-12-01T06:38:40Z")
> [@](#): > > \*Originally posted by Angel of the Lord \* > \*\*Er, **DaPearl** , maybe I missed this in your posts, but. . ._were_ you speeding? 😕 \*\* As your attorney, I advise you not to answer that! **Astro,** I have no doubt some radars, possibly the newer units, can work that way. > [@](#): > > The strongest return signal, usually reflected from highway signs, bridges or other objects, is assumed to be the cop car speed. Aye, there’s the rub. A lot of “assumed” in there. With a passel of objects and a multiple of vehicles in the area, no radar is intelligent enough at the current state of the art to absolutely distinguish between those objects at all times. And a mis-identification would result in an unreliable display. There is no such ambiguity of the cop car’s speed if the radar is connected to the car’s wheels or speedometer, and that speed is either added or subtracted from the measured, relative speed of the subject. [Previous page](https://boards.straightdope.com/t/got-a-ticket-need-info-on-speed-radar-laws-out-of-state-stuff/215691.md?page=1)