Truvelo question 1 and question 2

[mybrainhurts]

Some Truvelo cash harvesters have sensors that extend to both sides of the road.

One near me can be turned round to face either direction, with sensors from kerb to kerb on both sides.

Question 1...

If the car approaching me is exceeding the limit and we both cross the sensors at precisely the same moment, how do the processing dwarfs know which one of us is speeding?

Question 2...

If I overtake a lorry at warp speed, and time it so that I cross the sensors as I'm hidden from the camera by the lorry, will the lorry get done for 150mph...?

Edited by mybrainhurts on Monday 20th August 02:13

[oldsoak]

AFAIK, these cameras police only ONE side of the road at a time...if the lens is pointing AT you, then your side of the road is 'it'. Conversely if all you see is the back of the machine on approach, then the opposite carriageway is being policed.

[bryan35]

truvelos use 3 pressure sensors on the road. call them A B and C.
The time from A to B is measured, and compared with the time B to C. If they are the same (which they should be) and the time is too short, you get a nice flash. The camera can also determine which direction the car is travelling in, as the other direction would be C B A. If you were to cross the sensors at exactly the same time as a car in the other direction, which you can't as the sensor is 3 seperate strips, the timings would mess up and the software would abort. So,
If you got there slightly before him, you'd get the ticket as the sensors would reveal the direction of travel. If he got there bofore you, he'd get the ticket for the same reason. If you both got there together, you'd get a mish mash of maybe A+C BB C A - software aborts.

The error is easy to detect when you think,

you pass A then B in lets say 5 millisecond, he then passes C 1 millisecond later - timings don't tally - abort.

you pass A then B in 5 millisecons, then B to C in 5 milliseconds, then he passes C 1 millisecond later - you get the ticket as the timings did tally.

typically they do only trigger in 1 direction, as the photo for the other direction is of the side of a vehicle with no reg plates.

Edited by bryan35 on Monday 20th August 09:17

Edited by bryan35 on Monday 20th August 09:19

[Flat in Fifth]

One thing that has never been satisfactorily answered in my view is, what is the method of corroboration for truvelos?

Gatso get the carriageway markings, and assuming the photograph timing is accurate one and all can make a measurment and calculation from those.
But with Truvelos? It is simply those three little lines on the road, if vehicle is on them or not. But what corroboration as to accuracy of reading?

[mybrainhurts]

That worries me too...my local camera is in a 50.

From the millidoohdah reply, it appears I can't get a lorry done for 150...?

Arse, that would have been a wheeze...

Suppose the consolation prize is that I can get away with huge velocity if I'm hidden by the lorry...




Edited 'cos there's no g in consolation....

Edited by mybrainhurts on Monday 20th August 12:34

[smeggy]

Flat in Fifth said:

One thing that has never been satisfactorily answered in my view is, what is the method of corroboration for truvelos?

Gatso get the carriageway markings, and assuming the photograph timing is accurate one and all can make a measurment and calculation from those.
But with Truvelos? It is simply those three little lines on the road, if vehicle is on them or not. But what corroboration as to accuracy of reading?

The white lines are a couple of meters further down from the pressure sensors; IIRC, 1.8, 2.0 and 2.2 meters from the last strip (the ones local to me are anyway).

Based on the speed reading derived from the strips (the primary measurement), the processor will calculate the time delay for when the front wheels should theoretically be on the 2nd white line. The single photo will be taken after this time delay (from passing over the last strip). Unlike a Gatso, the time delay is variable.

The secondary measurement must be within 10% of the primary, hence the spread of the outside two lines of +/-10% from the target (middle) line; hence the wheels must be within these lines for the prosecution to stand. The photo won’t show the wheels within the lines if the primary reading was in error my more than 10%.

However, the lower of the primary and secondary reading should be that used for prosecution (this is true for Gatsos, not sure about Truvelos); I don’t believe the vehicle speed can be deduced from use of these lines.

[smeggy]

mybrainhurts said:

Some Truvelo cash harvesters have sensors that extend to both sides of the road.

One near me can be turned round to face either direction, with sensors from kerb to kerb on both sides.

Question 1...

If the car approaching me is exceeding the limit and we both cross the sensors at precisely the same moment, how do the processing dwarfs know which one of us is speeding?

Question 2...

If I overtake a lorry at warp speed, and time it so that I cross the sensors as I'm hidden from the camera by the lorry, will the lorry get done for 150mph...?

1) Like this?



I'll try to find out if there are separate sensors for each lane or if they are shared. I don't know of no reason why both lanes can’t be enforced.

2) No, the direction will be a bit of a givaway (as well as the delayed photo). If you time it right you won't get done either


I’ve watched multi-lane (same direction) Truvelos remain quiescent (not triggered) by speeding ambulances when there is traffic in the other lanes (otherwise they do flash).

[Plotloss]

With regards to corroboration of a Truvelo, presumably thats the fact that Piezo strips are a defined set distance apart and that theres 3 of them on each carriageway.

[Flat in Fifth]

smeggy said:

Flat in Fifth said:

One thing that has never been satisfactorily answered in my view is, what is the method of corroboration for truvelos?

Gatso get the carriageway markings, and assuming the photograph timing is accurate one and all can make a measurment and calculation from those.
But with Truvelos? It is simply those three little lines on the road, if vehicle is on them or not. But what corroboration as to accuracy of reading?

The white lines are a couple of meters further down from the pressure sensors; IIRC, 1.8, 2.0 and 2.2 meters from the last strip (the ones local to me are anyway).

Based on the speed reading derived from the strips (the primary measurement), the processor will calculate the time delay for when the front wheels should theoretically be on the 2nd white line. The single photo will be taken after this time delay (from passing over the last strip). Unlike a Gatso, the time delay is variable.

The secondary measurement must be within 10% of the primary, hence the spread of the outside two lines of +/-10% from the target (middle) line; hence the wheels must be within these lines for the prosecution to stand. The photo won’t show the wheels within the lines if the primary reading was in error my more than 10%.

However, the lower of the primary and secondary reading should be that used for prosecution (this is true for Gatsos, not sure about Truvelos); I don’t believe the vehicle speed can be deduced from use of these lines.

Problem is though that I've seen at least two sites now where it appears as if the section of road with the pressure sensor strips has been overlaid with red paint or similar surfacing. This it's not possible to see the lines where the channels have been cut into the tarmac to lay the cables. Thus no possibility for genuine after the event corroboration. At least with Gatso lines a site visit should result in the ability to make a check.

[smeggy]

Flat in Fifth said:

Problem is though that I've seen at least two sites now where it appears as if the section of road with the pressure sensor strips has been overlaid with red paint or similar surfacing. This it's not possible to see the lines where the channels have been cut into the tarmac to lay the cables. Thus no possibility for genuine after the event corroboration. At least with Gatso lines a site visit should result in the ability to make a check.

I’ve never seen paint over strips, but I see what you mean.

I can only assume the installers used an approved means of measuring and recording the distances before activating the system, hence that is good enough for submitting as evidence (the strips can’t move much over time). Of course this doesn’t help Joe Public in anyway, but we know the authorities have a habit of heaping ‘tough sh*t’ on us.....

I think all one can do is ask to see approved evidence of correct set-up.

[smeggy]

Plotloss said:

With regards to corroboration of a Truvelo, presumably thats the fact that Piezo strips are a defined set distance apart and that theres 3 of them on each carriageway.

I thought it was only RedSpeed that used three strips? The Truvelos I’ve seen use two pairs of strips.

[Flat in Fifth]

smeggy said:

I’ve never seen paint over strips, but I see what you mean.

First time I noticed it was in some/all(?) of the local scamp sites which use Speedvision 2/3 and use piezo-electric strips buried in the road.

The grooves in the road where the strips are buried plus two white paint strips were a dead giveaway to the site, further examination reveals the grey post that the van plugs into.

Now they have put red paint and white speed roundels over the buried strips and (I suspect) use the white borders of the red painted area as camera aiming / focussing / measurement tools. To be fair I've also seen some where there are additional (faint) white marker lines. Deliberately faint lines or old fading marks no idea frankly.

Anyway I put two and two together, got five, as you do, realised this was a subtle way of concealing the site, and looked around a bit, then found a Truvelo site similarly adorned. I forget where, not on our patch anyway, maybe just a coincidence, who knows, who cares.

[Hooli]

the old 'speeding truck' game used to be fun with gatsos too i miss it now & then