[TCUG] Re: Passively safe poles
- From: "Gollop, Alistair J" <Alistair.Gollop@xxxxxxxxxxx>
- To: <tcug@xxxxxxxxxxxxx>
- Date: Thu, 14 Jun 2007 10:06:54 +0100
Carole
Having had an opportunity to use a few different types of poles, I would
suggest that, as you have found from your practical experience, that the
mix of equipment for different applications needs to be looked at
carefully. There would appear to be two types of solution commercially
available at this time in the UK for electrical isolation of the poles,
the Snatch-plug and the Electrical Isolator. It may be found that one of
these is better for poles which are designed to breakaway, whereas the
alternative may be preferential for poles which yield.=20
The use of Crash-friendly products is gradually spreading, with the
realisation that they are an additional tool in the signal engineers
design toolkit, but until a consensus is reached amongst the signal
engineering community, about how different mixes of products should be
utilised it will continue to cause confusion and misunderstanding.
In answer to the previous question regarding the use of passively safe
short poles, the TA specifies that poles used in the vicinity of where
NMU's are likely to be, must not be Non-energy (N.E.)Absorbing types,
but Low-energy (L.E.) and High-energy (H.E.) are permissible. Taking
this into account, if an errant vehicle were to strike it, it would be
unlikely that the pole would "fly off", but instead yield in front of
the vehicle. An electrical isolator system is still required for ELV
circuits on Crash-friendly poles.=20
regards
Alistair Gollop MIHIE, MIET, Traffic Signal Engineer
Mott MacDonald Ltd, Stoneham Place, Stoneham Lane, Southampton, SO50 9NW
Office: 023 8062 8725 Mobile: 07717 224366 Fax: 07092 218790=20
Email: alistair.gollop@xxxxxxxxxxx
This message is from Mott MacDonald Limited, registered in England
number 1243967.
Registered office: St Anne House, 20-26 Wellesley Road, Croydon, Surrey,
CR9 2UL, England.
-----Original Message-----
From: tcug-bounce@xxxxxxxxxxxxx [mailto:tcug-bounce@xxxxxxxxxxxxx] On
Behalf Of Probert, Carole
Sent: 14 June 2007 08:25
To: 'tcug@xxxxxxxxxxxxx'
Subject: [TCUG] Re: Passively safe poles
Yes we have installed standard short poles with a termination door with
the DOT plug, and it is necessary to disconnect ELV.
That said we have had a couple of 4m knock downs on high speed roads and
the plug and socket have not pulled apart because the aluminium poles
did not shear.
We now use the NAL system, which disconnects even if the pole doesn't
shear, and we consider it has much greater maintenance benefits. This
system leaves existing cabling connected as normal, and thus tethers the
pole. If you require further information give me a call.
Regards
Carole Probert
Traffic Signal Design Team Leader
AmeyMouchel (Area 9)
Tel: 01905 683219
Featurenet: 7969 3219
Mobile: 0774 871 2946
=20
-----Original Message-----
From: tcug-bounce@xxxxxxxxxxxxx [mailto:tcug-bounce@xxxxxxxxxxxxx]On
Behalf Of Oliver David B
Sent: 13 June 2007 10:32 am
To: tcug@xxxxxxxxxxxxx
Subject: [TCUG] Passively safe poles
Regarding passively safe signal poles.
On standard and 6m poles the dot plug system is commonly used for
electrical connection so that the connection breaks away when the pole
snaps. Has anyone installed short poles (2m) to house a solitary PB unit
and, if=3D so, is it necessary to specify a wide based pole so that DOT
plug can be used=3D for disconnection, or is it considered unnecessary
from an electrical safety po=3D int of view to disconnect ELV.
That obviously leaves out the fact that, should the pole shear on impact
th=3D ere seems to me to be a significant danger of the free pole,
weighted by the PB, travelling through the windscreen with obvious
consequences. That begs the question, notwithstanding the argument about
the validity of passively safe poles as a whole, as to whether short
poles should be passiv=3D ely safe.
Any feedback/info would be appreciated.
Thanks
Dave Oliver
Traffic Signals Manager
Highways & Traffic Signals Website address www.newcastle.gov.uk
Engineering Services Newcastle City Council
Stratford House Phone +44 (0)191 278 3934
Newington Road East Mobile +44 (0)797 6122403
Newcastle upon Tyne Fax +44 (0)191 278 3805
NE2 1PX e-mail
david.b.oliver@xxxxxxxxxxxxxxxx
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Infrastructure Services registered office The Sherard Building Edmund
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