speed advisorys on Western Highway.

Submitted: Wednesday, Mar 14, 2007 at 19:31
ThreadID: 43255 Views:2919 Replies:9 FollowUps:13
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Just drove from Melbourne the other day and used the speed advisorys on the Western Highway. I lined up the speedo at spot on 100kph and the first one gave me a reading of 90kph! Well I got to the second one and lined the speedo up at 100 again and the second one gave me a reading of 94kph which is more acceptable taking into account speedo errors and the like.

But you have to ask the question... Are they giving under readings to give you a false sense of security so you think it's safe to push speeds a little higher, just enough so they can ping you on the next speed trap?

I think its appropriate that they are called speed ADVISORYS. for such a purpose.

Just another conspiracy theory and something to chew on for a while.

What do you think?
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Reply By: Andrew from Vivid Adventures - Wednesday, Mar 14, 2007 at 19:52

Wednesday, Mar 14, 2007 at 19:52
In my experience they are easily messed up when in the general proximity of other vehicles smaller or larger.

When I am out there on my own, they seem to give spot on readings with my GPS.
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Follow Up By: On Patrol (Aust.) - Wednesday, Mar 14, 2007 at 21:08

Wednesday, Mar 14, 2007 at 21:08
Andrew I would totally agree with that, also checking with the GPS.

I tend to use my gps to set the cruise control nowadays especially in Vic.
Colin.
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Follow Up By: Bonz (Vic) - Wednesday, Mar 14, 2007 at 22:15

Wednesday, Mar 14, 2007 at 22:15
I always drive on the GPS these days, I feel naked without it
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Follow Up By: Pajman Pete (SA) - Friday, Mar 16, 2007 at 07:37

Friday, Mar 16, 2007 at 07:37
"I feel naked without it" Now that is a frightening mental picture.

I think you might be using it wrong Bonz...

Pete
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Reply By: Member - Doug T (W.A) - Wednesday, Mar 14, 2007 at 22:48

Wednesday, Mar 14, 2007 at 22:48
Yeh I a too agree with the other two on that ....But Bonz you might be able to pick up some undies at St Vinnies mate
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Reply By: Hairy - Wednesday, Mar 14, 2007 at 22:55

Wednesday, Mar 14, 2007 at 22:55
What are they and how do they work?
Cheers
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Follow Up By: Member - Phil G (SA) - Wednesday, Mar 14, 2007 at 23:01

Wednesday, Mar 14, 2007 at 23:01
Hairy, they are speed indictors on the freeways that you drive under and they display your "exact" speed, so you know how incorrect your speedo is.
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Follow Up By: Hairy - Wednesday, Mar 14, 2007 at 23:32

Wednesday, Mar 14, 2007 at 23:32
Not real exact by the sounds?
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Follow Up By: Member - Phil G (SA) - Thursday, Mar 15, 2007 at 09:52

Thursday, Mar 15, 2007 at 09:52
If you've got a few vehicles together, hey seem to get confused, but if you're on your own, I've found them to be the same as my GPS.
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Follow Up By: Robin - Thursday, Mar 15, 2007 at 14:17

Thursday, Mar 15, 2007 at 14:17
They are designed to be exact but easily subject to interference.

They are Droppler Radar based devices

Robin Miller
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Follow Up By: Member - JohnR (Vic)&Moses - Thursday, Mar 15, 2007 at 15:26

Thursday, Mar 15, 2007 at 15:26
They seem all over the place where some vehicles are travelling one behind the other. For some reason my smaller car which has a very accurate speedo by GPS gets a higher reading than the vehicles travelling at the same speed along the highway!

Robin, is the Doppler radar more subject to interference than the bands used by government for revenue collection?
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Follow Up By: Robin - Thursday, Mar 15, 2007 at 15:53

Thursday, Mar 15, 2007 at 15:53
The readout is independant of the vehicle mass John.

There's a few different types of revenue collection units, and they basically fall into two catergorys.

Your overhead ganty sort , which is similar , and the roadside units.
(Hand helds are different again and generally spot laser beam)

These units are much more expensive and have better beam tolerances.

Also , revenue ones are verified by pictures which should ensure a low error rate.

Robin Miller

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Follow Up By: Member - JohnR (Vic)&Moses - Thursday, Mar 15, 2007 at 18:23

Thursday, Mar 15, 2007 at 18:23
Robin, I hadn't thought that there would be anything to do with the vehicle mass. Just distinguishing the vehicle as having an accurate digtal readout to compare the Vicroads machine. Just yesterday with three vehicles in the same lane at the same speed gave three different read speeds. The reflection of one vehicle off another I guess is the problem for accuracy.
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Follow Up By: Andrew from Vivid Adventures - Friday, Mar 16, 2007 at 00:30

Friday, Mar 16, 2007 at 00:30
Not all Vic gov ones are verified by pictures - eg. the mobile ones mounted on the side of vehicles.

It is one thing, that with my scientific background, that annoys me - every scientific device has an accuracy figure, which is usually a complex figure that varies in the circumstances, so temperature, operating time, speed, etc., might influence the accuracy which might be +/- 0.1% of +/- 5.0% (say). This information could be very relevant, particularly in Vic where they'll ping you for a couple over.

I am almost certain that when I was done on the Western Highway more than a year ago now (near Stawell) by a mobile device the operator got it wrong because there were two other vehicles around and the device was not reading my speed effectively. Interestingly, despite refusing my objections top the notice twice, and my election to see them in court, they have not pursued it, and I have been told unofficially won't be.

BTW, There is quite a bit of information on the web about Victorian Speed cameras including a review - from memory, Auditor General's Department.

Unfortunately, however, it seems to be the accepted wisdom in courts all over this fine country, that a policeman handling a scientific instrument on his own with little training and no knowledge of the science, and with few requirements to check his reading, will have his word accepted over individual turkeys like me, and we are effectively giulty until proven innocent. From memory some of their cameras are using multiple technologies - so there is a check and balance there, but in the case of the mobile guys, whatever the reading is on his display, that applies to whomever he wishes it to.

Cheers
Andrew.
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Reply By: Kumunara (NT) - Wednesday, Mar 14, 2007 at 23:47

Wednesday, Mar 14, 2007 at 23:47
Goldsahara

The variation in speed could be your driving. (90+ 94 km/h).

The best way to check your speedo would be a GPS.

It is common for speedos to be out. My patrol speedo reads about 3 km/h under my actual speed. The wifes Magna speedo reads about 5 km/h over the actual speed.

PS. I am a bit worried about your mental health by some of what your wrote. I hope you wrote it tongue in cheek. Your not going paranoid I hope.

Tjilpi

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Follow Up By: Goldsahara - Thursday, Mar 15, 2007 at 14:10

Thursday, Mar 15, 2007 at 14:10
Don't worry I'm not paranoid, it was all tongue in cheek stuff and an experiment to see what kind of replies I would get and am satisfied that we haven't collectively lost it yet LOL.

And yes they are the two before Ballarat.
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Reply By: True Blue - Thursday, Mar 15, 2007 at 00:41

Thursday, Mar 15, 2007 at 00:41
Goldsahara. If the speed advisorys are the 2 before Ballarat, they have been just like you say for some years now. I have travelled past both of these advisorys at exactly the same GPS posted speed and read differences between the two of about 4kph, and have done so on many occasions.
They have shown the difference now for so long I can only assume that it is deliberate, after all it is Victoria. The same state with Vic Roads who admitted last year that they deliberately slowed Melbourne's traffic down by ensuring that traffic lights are out of sequence. Road rage anyone?
Get rid of them and have our roads controlled by Canberra. The locals can't get it right and basically don't want too.
Wayne.
AnswerID: 227572

Reply By: Andrew from Vivid Adventures - Thursday, Mar 15, 2007 at 10:02

Thursday, Mar 15, 2007 at 10:02
One other thing... if you have the choice between conspiracy and stuff up take stuff up - more times than not, it is just a plain stuff up.
AnswerID: 227616

Reply By: Kumunara (NT) - Thursday, Mar 15, 2007 at 23:51

Thursday, Mar 15, 2007 at 23:51
Goldsahara

I appreciate your sense of humour.

It also prompts come interesting and informative discussion.

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Reply By: Member - Beatit (QLD) - Friday, Mar 16, 2007 at 09:41

Friday, Mar 16, 2007 at 09:41
In a similar vein, up here in Brissy they have a couple of readers on the Ipswich toll road with the idea of slowing you down to the obligototy 60 at the toll booths. A smily face pops up once you hit 60 or below. I have had more than a couple of occassions of slowing to 60 - the bride is looking for the smily face and I am in trouble if it doesn't appear. So it is most annoying to have a big semi coming up behind at 70+ and the radar is focussing on it and not me while I'm arguing with her about my speed. I can see the guy in the mirror closing fast and my speed does not register at all.

Nice system if they now decide to use the same setup for enforcement.

Kind regards
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Reply By: Im.away - Friday, Mar 16, 2007 at 10:14

Friday, Mar 16, 2007 at 10:14
I assume from your log-in name that you drive a Landcruiser. LAndcruisers generally don't have a reputation for speedo error. I have recently driven a Nissan Navara (latest model) provided by my employer. The rig is dead standard - no funny sized tyres to induce speedo error - and the speedo is 15kph out at the legal speed limit of 110 kph here in WA.

I've checked this against two different GPS units and I've driven past several cops with the speedo indicating 125 kph. No reaction at all from the cops.

I think that such an error is completely unacceptible in modern vehicles. Sure, if I drove according to the speedo I would never get a ticket, but the trouble is that we use our trip meter to invoice our customers and that would mean ripping ourselves off.

We now use the trip meter on the GPS.
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Follow Up By: Member - Beatit (QLD) - Friday, Mar 16, 2007 at 15:07

Friday, Mar 16, 2007 at 15:07
That's handy except when the customer travels the same route in the same vehicle and comes up with another "rip off" story!

Kind regards
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