[TCUG] Re: Red Light 'Safety' Cameras

I could not agree more -  Health and Safety (and I think legislation?)
being the major issue here.

If cables of differing voltages are run in the same duct, additional
voltage can be generated in
the "lower voltage" through inductance.  Even if the power cables carry the
same voltage, there
is still the problem of an engineer mistaking a live cable for one he (or
she) has isolated by removing
signal supply fuses or switching the controller off.

In no way would I (knowingly) allow 240V mains for a supply other than for
traffic signals in the same duct.
I say "knowingly" because we have been caught out in the past
(and this reminds me of a particular instance I need to chase)

Regards (and Happy Christmas to one and all)

Grahame Bath
~~~~~~~~~~~~~~~~~~~~~~~~
Grahame Bath
Senior Engineer, Traffic Systems
Traffic and Road Safety Group
Surrey County Council

020 8541 7346 (Tel)
020 8541 7366 (Fax)
~~~~~~~~~~~~~~~~~~~~~~~~


                                                                                
                                                            
                      "Carter, Terry (via                                       
                                                            
                      secretary)"                   To:       
"'tcug@xxxxxxxxxxxxx'" <tcug@xxxxxxxxxxxxx>                                   
                      <Terry.Carter@xxxxxxxx        cc:                         
                                                            
                      scc.gov.uk>                   Subject:  [TCUG] Re: Red 
Light 'Safety' Cameras                                         
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                      tcug-bounce@freelists.                                    
                                                            
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                      15/12/2003 13:24                                          
                                                            
                      Please respond to tcug                                    
                                                            
                                                                                
                                                            
                                                                                
                                                            




Tony
I think that there are two issues.  The first is about isolation of the
cables within the duct.  If a duct is shared you need to be able to isolate
both installations from one point for Health and Safety reasons, so if the
camera is powered from the signal controller supply that should
theoretically be OK. However it would mean that if there was a need to
isolate the camera the signals would be off and vice versa.  So not good
practice, and particularly difficult if the maintaining companies are
different.  The second is about running cables of significantly different
voltages though the same duct.  In this case damage to the duct or failure
of a cable can obviously lead to feedback of inappropriate current to some
circuits.  Thus additional cable protection is necessary.  It is sometimes
possible to insert a smaller duct inside an existing one but it is usually
not easy and a desperate last resort.  Altogether better to put a separate
duct and power supply in for the camera.
Terry

-----Original Message-----
From: Tony Sharp [mailto:Tony.Sharp@xxxxxxxxxxxxxxxx]
Sent: 15 December 2003 12:46
To: tcug@xxxxxxxxxxxxx
Subject: [TCUG] Red Light 'Safety' Cameras


I wonder what members views are on the use of traffic signal ducting by
red light cameras. One of the smaller signal companies (based in
Kidderminster) have now branched out into 'Safety' cameras. As part of
their works the propose to use traffic signal ducts (including those
going across carriageway) to run their cable through (including I assume
power cables to the camera)

My instinct is to resist such a move and insist on the installation of
a new ducting system (as was the case when I put some of the earliest
Red light cameras in some 15 years ago with Serco).

Do other users have any experience of this?

Regards

Tony Sharp
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