Truvelo - 1 flash or 2?

[MikeS48]

Well I got one red flash in my face on Sunday evening from Truvelo 5488, doing about 48mph in a 40 zone.
I'd plotted a route home (from Beverley to Preston) then decided to divert to Tesco's just outside Hull for fuel. The constant revised directions led me to turn my Satnav it off - otherwise I'd have been warned - doh! Ironically I was only going to Tesco because I had a 5p a litre off voucher - wow! I saved about £3.00!!!
So, one flash, not two. Has it snapped me? Or hasn't it? And even if it has, could it be a dummy, or out of film? And why would a Truvelo flash twice anyway, when there are no reference marks on the road, as with Gatsos?
I'll know by a week Sunday, I suppose, I'll let you know.

[shadamehr]

I have to confess, I know little about how Truvelos and Monitrons work.
But I was given to believe there was NO flash, be it Red IR or otherwise.
Certainly I believe a Truvelo also takes TWO photos, for position and speed measuring purposes.
But flash - even IR Red?
New to me.

Unless it senses when dark, and only does this on a night time - is that when this was?
Happy to hear the replies from them more in the know however, as this has me interested.

Here's keeping my fingers crossed you are ok though mate.
Though by your own tacit admission, if doing 48mph past a 40 Truvelo, I would have expected it to sting you alas mate.

(That's expected it to, not WANTED it to - I hate ALL cameras personally)

EDIT:

As to there not being any painted road measurement markings...

Alas, if I load that camera up into Google Earth or Google Maps, zoom in and go Satellite View, where I think I have spotted the camera (near the junction of Beverly Road and Downfield Avenue, just north outskirts of Hull on the A1079), then at that location, there ARE road markings - both in the form of the junction hatchings, that can be calibrated and used, but also, if you look carefully, additionally inside/Central Reservation Hatching Marks.

Any of these can be set up to measure the speed based on the resultant photos. All it needs to is take two photos, and measure where you where, compared to where you are on the second photo (thus establish distance), and the time taken. So any permanent road markings can be used alas.

[klystron_generator]

try this page for a brief summary

[Allen_EP]

There is a camera locally that has changed. Some months ago there were several Police cars at the spot along with a notice saying ‘Warning new Speed Camera under test’ the camera looks like a Peek camera. The original camera was a Gatso and in the centre of the rod with marking both sides of the road. The camera is set on a slight bend. The new camera is set pointing towards the oncoming traffic and could no way catch cars that are passing it only ones approaching it. This camera is on the PGPSW data base as a Gatso. Can anyone suggest what type of camera it could be.

[DennisN]

[MikeS48]

Thanks for the responses, guys.

Just to confirm, the one that flashed me, once only, was on Beverley Road, Hull, near the junction with Evergreen Drive. It was dark, and raining, so I didn't see any road markings, nor did I even see the camera until a split-second before it flashed, I'm ashamed to say - idiot! (even bigger idiot for turning my satnav off when I diverted for fuel - just to stop it re-directing me every 2 minutes. I was only using it as a camera-warning device, being in an unfamiliar area). The camera in question is labelled TRUVELO:5488@40 on my satnav screen.

You'll be pleased to know that by going off-route for fuel, leading to me turning the satnav off and not getting the warning, and possibly £60 and 3 points, I was able to save £3.00 by using my 5p a litre off voucher at Tesco - ROTFL, I think...

Antway, the flash was just like someone flicking a red light on/off very briefly - no dazzle, no after-image, you may not even spot it going off in daylight.

I've done some surfing - Truvelo UK have a site and there's a Truvelo product leaflet from their parent site in S Africa.

First of all, all Truvelos do flash - front-facing ones have a magenta filter to avoid dazzle and flash once only - which means they do only take one picture, whereas rear-facing ones flash twice and take 2 pictures.

The flash/photo is triggered by your front wheels compressing 3 or 4 buried piezo sensors (under the tarmac) in quick succession. The electronics calculate your speed from how quickly you pass over the sensors, and if you are exceeding the trigger speed - flash!

The pictures of the "works" inside the Truvelo box show a significant difference. The leaflet says they contain a 35mm camera using standard 36-exposure cassettes of colour or b/w film,(not digital) and that's just what it looks like in the photos on the leaflet. "Wow!", I thought, 36 shots and it's out of film, that must improve my odds. However, on the UK website, the back of the camera appears to have a massive film cassette attached to it, allowing Heaven knows how many shots. Can't really tell for sure, though.

Another feature of the Truvelo is an accessory called "Intelligent Flash Simulator" which can be put in the box when the camera itself is moved to another location. Yes, it flashes if the trigger speed is detected, but no camera - no film. The intelligent part is that it data-logs all it sees, speeds, volumes etc, which helps the operators in deciding where the cameras are most needed.

So a flashing Truvelo may not have a camera in the box, and it may have run out of film. Makes them seem almost generous, doesn't it?

So that's answered my own question really - front-facing - 1 flash, which is what I got, wait and see...

That's not the end of the story though. My original post queried the little matter of secondary confirmation of the vehicle's speed - like the Gatso road markings that we are all familiar with.

Truvelo's website covers secondary confirmation with a description (and photos) of 3 painted white lines on the road ahead of the piezo sensors. The middle line is 1.8 metres from the forward-most sensor, with the others being 18 cm on either side of it (plus 10%, minus 10%), so the 3 lines span 36 cm - about 14 inches. Unbelievably, I thought, an offending vehicle's front wheels will always be photographed within the span of the three lines. No mention of speed. How can that be? OK, the camera will fire whether you're just into the trigger speed, or double the limit! So the "decision" to flash can only be made after your front wheels have cleared the last of the sensors, and yet, no matter by what margin you are breaking the limit, the sole photograph is always taken when your car is 1.8 metres (± 10%) further along the road.

It's a bit like being Gatsoed and your vehicle always straddling the exact same check lines on the road, regardless of your speed - it doesn't add up. (Yes, I know there's 2 photos with Gatso...)

If speed is a function of time and distance, where is the "time" in Truvelo's secondary confirmation scenario? Once the vehicle has cleared the last sensor, time theoretically becomes of no further relevance in their system, because the vehicle's speed has by then been calculated.

And what about other speed limits? I see that there are several 60mph Truvelos further north on the A1079, and even one at 70mph. Do these rely on the same three-line "secondary confirmation" a mere 1.8 metres away? It takes less than 6/100ths of a second to cover 1.8 metres at 70 mph!

The only way this can work, as far as I can see, is if the electronics calculate a delay before firing the camera, proportional to the vehicle's calculated speed, to make sure its wheels are within the lines when the flash fires. This begs the question - is it truly a secondary confirmation if it relies on a re-working of the original speed data? I don't believe it is. How come they need 2 pictures if rear-facing, but only one for front-facing? The principle of speed = distance divided by time is exactly the same.

Anyone have any thoughts on this?

BTW, DennisN, how's Horace Bachelor these days?

[DennisN]

[GPS_fan]

[DennisN]

Well, and there's silly ole me thinking it was something complex.
_________________
Dennis

If it tastes good - it's fattening.

Two of them are obesiting!!

[GPS_fan]

It might be and I'm no expert, but that's an abridged version of what I think might happen.

Only Smarties have the answer, right
_________________
Andy
PocketGPSWorld.com supports Help for Heroes - Read here

[DennisN]

Well, help me out here - go back and pad it out somewhat - give me a few Page Downs and it'll sound much more like it (best done by editing your post, by the way, so that we don't notice it).
_________________
Dennis

If it tastes good - it's fattening.

Two of them are obesiting!!

[MikeS48]

I think GPS_fan has sussed it out too, it's got to be a delay depending on your calculated speed, and hence what tiny decimal of a second it will take you to get to the check lines, and the flash only fires then.

If the picture shows you before the lines - you weren't going over the limit; and presumably if you've crossed over them, you weren't speeding either (work that one out!). In either case, unless you are snapped within the check lines, it doesn't count as a pull. Mr Truvelo puts his hand up, says, "Sorry, messed up on that one, ignore it".

So I although I would still argue that Truvelo's "secondary" check is a re-working of their own measurements, I can see why they say that if your front wheels are not within the check lines they don't count it as an offence and it's discarded.

It's not half as simple as Gatso's 2 pictures and 30 yards or so of white markings though. Anyone could work out their speed using those. And the irony is that Truvelo also take 2 pictures when rear-facing - but definitely only one when it's "in your face".

Another thing, Humberside Police won't show you the photo unless you contest the charge, which brings the risk of it costing you a lot more than a fixed penalty.

Oh! didn't I mention it? Yes, the nice white envelope landed on my mat on Monday morning - eight days later. Banged to rights, own stupid fault etc etc. So I'm not complaining and it has made me slow down - a bit. Shame, it's 17 years and about a third of a million miles since the last one!

Drive safely!

PS, RIP Horace Batchelor. 50 years??? I must be getting old...

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