bad press, page-17

re: bad press..speed cameras lie.. I've been reading with great interest your conversation on speed cameras.

I'm an Engie who works for a competitor for RDF (no prizes for guessing who) and it's interesting to see what the average techie out there thinks.

The embedded road sensors come in various forms but the two major types are colloquially called "loops" and "piezos." Loops are inductance loops and piezos are piezo-electric sensors. Do a search in Google and you can see the way these work.

The loops rely on inductance changes to determine presence and the piezos (which are strips) rely on pressure.

If you want to learn about non-embedded sensors like radar there is an excellent site called www.copradar.com which is probably the most complete site I've encountered.

The sensors are only part of the story. They tell us you're there and then we need controllers to ascertain how fast you're going, that's a different story all together.

Finally the highest layer is the software where we set the trigger level for the cameras. If it's a 100 zone then all vehicles travelling within an allowable range will not be photographed but if you exceed this then say cheese.

The digital image with all the embedded data is then sent via the network to a central location for processing.

TV news etc is a wonderful source for entertainment and women with pretty faces but if you want accurate info then it falls short. The truth is that speed and redlight cameras DO change drivers' behaviour and over time the death and disability rates due to vehicular accidents DO drop.

You can kid around all you like but people die or are disabled in a horrific fashion EVERY day of the week (quite often due to the actions of other drivers) and anything that helps minimise that is OK by me.

- Z