scouter4life

Too true, I didn't get out of a ticket, but got a reduced one when I went through a school zone 10 over, which would have been a $250 ticket (in '93). In AZ school zone speed limits are all day, I had just moved out here from IL where school zones sppeds were for when children were present, so I didn't slow down. I was nice to the cop adn apologized for not understanding, so he reduced it to a standard 10 over, which was about $80 if I remember. So it may not always get you out, but may get you a lesser ticket.

By the way, no radar, don't speed, but on the city streets now, they use cameras that were originally for red light runners, now magically (not sure how this one got pulled on us) they can use them to catch speeding through an intersection as they have sensors to determine speed. Radar doesn't work for this method. So anyone out there where they are using cameras to take a picture of red light runners, if they havn't already, they will probably start using them to catch speeders.

berg

VASCAR (Visual Average Speed Computer and Recorder) is really a stopwatch coupled with a calculator. Once a distance is entered, the operator pushes a button to start then stop the stopwatch. VASCAR displays the speed calculated from the distance entered and the time measured.

Thus, a VASCAR measurement depends on human input. Therefore, in order to make a VASCAR measurement as accurate as possible, the observer's/operator's reaction time must be as short as possible. (Reaction time is defined as "the time interval between an input signal (physiological) or a stimulus (psychophysiological) and the response elicited by the signal.)

What is considered "normal" human reaction time? First, let's take a look at the best: Drag racers. Average reaction time of (Top Fuel) drag racers at the 1997 U.S. Nationals was 0.124 ± 0.082 second. Imagine that our cop running VASCAR is a super cop, with drag racer like reaction times: What kind of error is introduced into the VASCAR speed measurement by a reaction time of 0.124 second? With the numbers testified to by our cop:

Distance
_________________ = Measured Speed

Real time ± Error


100
____________ = 60.096 feet/second (40.97 mph)

1.54 + 0.124


or


100
____________ = 70.621 feet/second (48.15 mph)

1.54 - 0.124

depending on whether the cop was 0.124 second too quick or too late.

The calculation above takes into consideration only one opportunity for error. However, the cop must not only start the VASCAR's stopwatch, but he also must stop it. Thus, he can introduce the error twice:

100
____________ = 55.928 feet/second (38.13 mph)

1.54 + 0.248


or


100
____________ = 77.399 feet/second (52.77 mph)

1.54 - 0.248

Looks like we are getting some error margin here: it is almost 15 mph. But wait a minute: the cop alleged that he clocked our man 66 mph (96.8 feet/second). If true, the elapsed time over 100 feet distance was 1.033 second. The error in speed reading introduced by human reaction time becomes even more severe:

100
_____________ = 78.064 feet/second (53.225 mph)

1.033 + 0.248


or


100
_____________ = 127.388 feet/second (86.855 mph)

1.033 - 0.248

WOW! An error margin of more than 33 mph! And remember, we assumed that the super cop in this example has reaction times similar to a drag racer!

Imagine if the cop is only human: Average adults show reaction times around 0.3 second -- it's not even worthwile to do the calculation. Obviously, we can no longer talk about accuracy and VASCAR in the same sentence. One can conclude that using VASCAR over a 100-foot distance cannot yield any accurate speed reading for the speeds alleged in our man's case. We come to this conclusion even before considering other sources of error, such as visual distortion introduced by the parallax effect.

And what about the law? This is what you find in § 3368 of Title 75 of the Pennsylvania Code:

(4) No person may be convicted upon evidence obtained through
the use of devices authorized by paragraphs (2) and (3) unless the
speed recorded is six or more miles per hour in excess of the legal
speed limit. Furthermore, no person may be convicted upon
evidence obtained through the use of devices authorized by paragraph (3)
in an area where the legal speed limit is less than 55
miles per hour if the speed recorded is less than ten miles per hour
in excess of the legal speed limit. This paragraph shall not apply
to evidence obtained through the use of devices authorized by
paragraph (3) within a school zone.

VASCAR is a device authorized by paragraph (3). Looks like even Pennsylvania lawmakers acknowledge that VASCAR is not a precise method for measuring speed.

scouter4life

Wow, my head hurts after reading that, but thanks for the info.

RedneckJeep

Is this a trick question??

berg

Hey! I didn't make this up. I just copied and pasted from a web site I found on google.

Looks impressive doesn't it?

Like I know WTF I'm talking about when it come to this s**t

JK-KJ

that's basically the point I was trying to make.....you don't have to be going 100mph to get caught, just normal driving can still get ya.

J2H

My brother's patrol car has a detector Detector and a Jammer. But I agree with N2, I dont intend to speed, but I usually do 10 over and even SCHP monitors that, so I want to know when I am being "pinged."

seer1

Man, if you need a radar detector you haven't added enough steel to your JK.

bigbluejk

Radar detectors allow you to pay more attention to the road without one you spend lots of time staring at the speedometer. They also warn you of accidents and construction zones in some areas. I think that responsible drivers should have them.

Brad2893

I've never had a detector, don't plan on it. These JKs are so bad over 120km/h that I never see the need.

Now, if I had my old man's corvette that would be a different story...or a Hemi swap...