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#1
Old 09-11-2006, 10:50 AM
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Join Date: Sep 2002
Location: Hampshire, England
Posts: 13,423
So what are these road surveying trucks doing, exactly?

In the past week or so, on three separate occasions I've seen slow-moving trucks on major roads here in the UK, with warning sigsn on the back saying "Surveying this lane". In addition to the standard flashing orange warning lights, on at least one of the trucks there seemed to be a flashing strobe light coming from underneath the truck, which I assume was some part of the "surveying" process.

So what exactly are they doing here? The strobing suggests some kind of digitisation, capturing lots of frames of the road surface as the truck moves along. Why do they need so much detail of a nondescript strip of asphalt? Are they just looking for defects that need fixing, or is there some more sinister purpose involved?
#2
Old 09-11-2006, 11:06 AM
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Join Date: Aug 2003
Location: Diogenes Club, TC, MN
Posts: 680
I am not familiar with road design specifics in England so I cannot do more than speculate. Hopefully it will do until someone more learned comes along.

Iíve done pavement survey analysis in the US and it involves determining the number of cracks in the pavement per area as well as the type of cracks (longitudinal/along road, lateral/across road, block/hatch pattern). The vehicle may have been photographing the pavement surface so that the condition could be evaluated in an office or perhaps by computer. Another pavement analysis tool is to evaluate the road deflection as a vehicle of known axle weight passes by, but with the flashes, it sounds more as if images were being taken.

In this case ďsurveyĒ would mean an evaluation rather than a measurement of heights and distances.
#3
Old 09-11-2006, 11:18 AM
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Join Date: Sep 2002
Location: Hampshire, England
Posts: 13,423
Thanks. That gave me some Google fodder, and I came up with this page from the US:

Quote:
The engineers did their work at night... "It's a very interesting method, using strobe lights that were directed at the pavement ... They drove every foot of our road system, taking 14-foot-wide samples at a time. It looked like a spaceship coming down the road. I had people calling me about a strange thing with flashing lights coming down the road, asking what was going on!"
Yup, sounds like what I saw.

Quote:
The digital image capture system, data storage system, and data analysis system are all housed in a customized van, which is operated at night, or in low light, with four strobe lights to guarantee optimal illumination for capturing high-resolution (1296 x 1024 pixel) digital images of the roadway.
Remind me never to accept an invitation to the Highways Department's holiday slideshow
#4
Old 09-11-2006, 11:41 AM
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Join Date: Aug 2003
Location: Diogenes Club, TC, MN
Posts: 680
And if you think the slide show would be boring, donít you dare check out the comparative pipe flow demonstration!

(Iím glad my speculation helped. Itís sometimes good to get lucky.)
#5
Old 09-11-2006, 12:32 PM
Charter Member
Join Date: Aug 2001
Location: Southeast MN
Posts: 5,910
Related question: Is that what I'm seeing on trucks in contruction areas?
There are off the back of the truck, only supported by the truck (i.e. no wheels)
they are a full lane wide 1-2 feet tall and a little longer than they are wide.
They are yellow and there may be two boxes (haven't seen one recentluyu, I don't rememeber)

I'd always guessed they were some sort of inspection device.

Brian
#6
Old 09-11-2006, 12:39 PM
Charter Member
Join Date: Jun 1999
Location: Milwaukee, WI
Posts: 27,538
Quote:
Originally Posted by N9IWP
Related question: Is that what I'm seeing on trucks in contruction areas?
There are off the back of the truck, only supported by the truck (i.e. no wheels)
they are a full lane wide 1-2 feet tall and a little longer than they are wide.
They are yellow and there may be two boxes (haven't seen one recentluyu, I don't rememeber)

I'd always guessed they were some sort of inspection device.

Brian
If I'm picturing it right, it sounds like the truck that drives behind a road crew. The yellow boxes are bumpers to absorb the impact of the moran flying down the emergency lane and not paying attention.
#7
Old 09-11-2006, 02:30 PM
Charter Member
Join Date: Mar 1999
Location: San Francisco area
Posts: 16,185
Quote:
Originally Posted by Joey P
If I'm picturing it right, it sounds like the truck that drives behind a road crew. The yellow boxes are bumpers to absorb the impact of the moran flying down the emergency lane and not paying attention.
Right - those are just big impact absorbers. Some are honeycomb aluminum, and some are foam blocks.

Depending on who made them, they're called cushions, attenuators, absorbers or similar names.

They also come in a surprising array of options.
#8
Old 09-11-2006, 03:13 PM
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Join Date: Sep 2006
Posts: 1
Ok a question I can answer

I work for a consultancy and involved in the analysis of such vehicles to carry out required maintenance.

There are a couple of machines this could be.

Firstly, twice annually the Highways Agency surveys the road using a survey machine called TRACS. The machine travels at traffice speed and measures rutting, texture, longitudinal profile and cracking. The first three measurements are collected through about 20 lasers in the front bumper. Cracking is collected by the use of strobe lights and a video collection of the surface of the road. The strobes ensure that the surface is collected in good light. The video is collected on a large hard disk and analysis through edge detection is used to detect the cracks. The video collection is housed at the rear of the vehicle and you shouldn't be able to see the strobe that well, you may catch a glimpse of it towards the surface of the road.

Secondly, the vehicle could be described as above in other posts. Our company works under contract to the Highways Agency (as do a number of other consultancies) to maintain their network. As part of that contract we have to carry out different forms of traffic management dependent on which lanes we're closing, the type of survey etc. A crash cushion is used in nearly all these circumstances; whether we're carrying out a rolling closure or a full lane closure. In a full lane closure these crash cushions are also able in most cases to carry the cones with which the closure is made (if not the crash cushion sits behind the cone laying truck). The lads laying the closure have to carry out some extremely dangerous tasks - the traffic approaches at 70mph+ and timing is everything-many are killed each year. The crash cushion lowers the protective cushion for protection and usually has an amber light to warn traffic of that overhang at the rear. These vehicles will deflect and absorb a car quite easily (the cushions are for 1 hit only!), however a truck will wipe it out, which happens not infrequently. I know personally of one survey where the first the surveyor knew of trouble was watching the cushion fly past them while surveying in a slow moving vehicle! The crew and truck driver survived, both vehicles were a right off. However, the surveyor was protected.

Hope that helps
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