Tower Bridge London
Discussion
muffles said:
i guess they must be forward-facing cameras? i used to travel over tower bridge on my way to work (bike) before i decided to go the rotherhithe tunnel way...i never spotted any speed cameras, only the congestion charge ones! where are they? 
They are SPECS cameras & they double up with loops in the surface to also prosecute over weight vehicles.
vonhosen said:
They are SPECS cameras & they double up with loops in the surface to also prosecute over weight vehicles.
Interesting. Can you confirm that VH?
Being the great engineer that I am, I wouldn't have thought that induction loops could infer the mass, conductive loop or otherwise, of a vehicle with any significant precision and accuracy.
smeggy said:
vonhosen said:
They are SPECS cameras & they double up with loops in the surface to also prosecute over weight vehicles.
Interesting. Can you confirm that VH?
Being the great engineer that I am, I wouldn't have thought that induction loops could infer the mass, conductive loop or otherwise, of a vehicle with any significant precision and accuracy.
There you go
smeggy said:
Being the great engineer that I am, I wouldn't have thought that induction loops could infer the mass, conductive loop or otherwise, of a vehicle with any significant precision and accuracy.
Going back 20 yrs now, I used to have a customer based in Nottingham who made such systems - although I don't remember exactly how they worked, they could weigh vehicles at motorway speeds. It was quite tricky to do it at speed then, but electronics has come on a long way since.
smeggy said:
vonhosen said:
They are SPECS cameras & they double up with loops in the surface to also prosecute over weight vehicles.
Interesting. Can you confirm that VH?
Being the great engineer that I am, I wouldn't have thought that induction loops could infer the mass, conductive loop or otherwise, of a vehicle with any significant precision and accuracy.
I have often wondered if they would do this. The way I would imagine it to work is when the truck or whatever passes over the loop it creates some sort of pattern that will be possibly unique to a type of vechicle and they can tell what type of vechicle it is passing over rather than the weight of it. This is how the coin mech in a vending machine works, someone puts thousands of each type of coin in and records them as each denomination. The coin mech can then tell what type of coin is passing through.
I would imagine it is possible to build up some sort of database of vechicles too.
If the loops are piezoelectric strips rather than inductive detectors then weight activation would be possible, but neither I nor the ABD know whether the loops mentioned are used for the purpose suggested. Interested to see what emerges!
As to the 20 mph limit, we discovered that it's there to protect the bridge structure, but then there's the weight limit so it's less justifiable. Enquiries we've made get responses which don't quite know why it's still there or whether it should stay or go. But it's definitely still active in terms of detection as otehrs have pointed out.
As to the 20 mph limit, we discovered that it's there to protect the bridge structure, but then there's the weight limit so it's less justifiable. Enquiries we've made get responses which don't quite know why it's still there or whether it should stay or go. But it's definitely still active in terms of detection as otehrs have pointed out.
vonhosen said:
smeggy said:
vonhosen said:
They are SPECS cameras & they double up with loops in the surface to also prosecute over weight vehicles.
Interesting. Can you confirm that VH?
Being the great engineer that I am, I wouldn't have thought that induction loops could infer the mass, conductive loop or otherwise, of a vehicle with any significant precision and accuracy.
There you go
Thank you.
However, following some research I'm now convinced that induction loops do not determine the mass of a vehicle. The induction loop detects vehicle presence (just like they always have done); use of ‘Class 1’ piezo electric sensors enable weigh-in-motion (a gold star to turbobloke).
I realise I'm probably being pedantic but there you go.
deva link said:
Going back 20 yrs now, I used to have a customer based in Nottingham who made such systems - although I don't remember exactly how they worked, they could weigh vehicles at motorway speeds. It was quite tricky to do it at speed then, but electronics has come on a long way since.
You can’t use induction loops to measure metallic mass. Different configurations of the same conductive mass (spherical or looped, height, offset from centre, conductivity of metal) will result with different reactance of the coil. No amount of clever elec-trickery can compensate.
smeggy said:
deva link said:
Going back 20 yrs now, I used to have a customer based in Nottingham who made such systems - although I don't remember exactly how they worked, they could weigh vehicles at motorway speeds. It was quite tricky to do it at speed then, but electronics has come on a long way since.
You can’t use induction loops to measure metallic mass. Different configurations of the same conductive mass (spherical or looped, height, offset from centre, conductivity of metal) will result with different reactance of the coil. No amount of clever elec-trickery can compensate.
The link that VH provided doesn't actually say they weigh the vehicles - merely that they take all sorts of other readings and then check the vehicle classification using ANPR. So it could be that they're simply looking for max laden/unladen weight (or whatever) figures from the DVLA database and they prosecute based on those.
deva link said:
The link that VH provided doesn't actually say they weigh the vehicles - merely that they take all sorts of other readings and then check the vehicle classification using ANPR. So it could be that they're simply looking for max laden/unladen weight (or whatever) figures from the DVLA database and they prosecute based on those.
Yes that could well be; however, given that the link stated that piezo-electric sensors are used within the Weight Limit Enforcement system I can only conclude these sensors are used to directly measure weight - speed is done by other means, so what else could these sensors be used for?
Note, traffic systems exist which use piezo sensors for weigh-in-motion stations.
I assume the induction loops are used to identify the beginning and end of vehicles (i.e. which axles belong to a vehicle mass).
smeggy said:
deva link said:
The link that VH provided doesn't actually say they weigh the vehicles - merely that they take all sorts of other readings and then check the vehicle classification using ANPR. So it could be that they're simply looking for max laden/unladen weight (or whatever) figures from the DVLA database and they prosecute based on those.
Yes that could well be; however, given that the link stated that piezo-electric sensors are used within the Weight Limit Enforcement system I can only conclude these sensors are used to directly measure weight - speed is done by other means, so what else could these sensors be used for?
It mentions height is measured. Ultrasound usually uses piezo-electric sensors. Could also be used for axle counting.
Inductive loops are used to give the type of classification of vehicle. if the sensor deems the vehicle over a certain magnetic signature it will send a signal to the camera to take a picture.
ANPR is then used to cross check with the DVLA and only then a a NIP will be issued if the DVLA records show that the weight limit was exceeded.
ANPR is then used to cross check with the DVLA and only then a a NIP will be issued if the DVLA records show that the weight limit was exceeded.
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