[TCUG] Pedestrian Nearside Indicators - louvres and restricting viewing angles - an update
- From: Saffer Howard <Howard.Saffer@xxxxxxxxxxxxxxxx>
- To: "TCUG (E-mail)" <tcug@xxxxxxxxxxxxx>
- Date: Wed, 23 Jun 2004 15:48:40 +0100
SORRY for the delivery of the earlier incomplete e-mail - this is the complete
version (you can 'bin' the one from earlier today - which included all those
libellous statements ...... only joking!) - Howard Saffer
****************************************************
From recent correspondence on the TCUG list, many users will no doubt be aware
that we (Sheffield City Council) have been investigating various means of
restricting the angle of viewing of Pedestrian Nearside Indicators (PNIs) at
signalled junctions, where visibility of these signals from one crossing
through to another (read-through - or see-through, as you will) can be a
serious problem. I suspect this may be even more of a problem for pedestrians
who are unused to Puffin crossings and are initially looking for a far-side
signal.
After discussion and developments in the last two weeks - this e-mail is
intended as an update for all users.
Preamble - our experience of PNIs in practice is that the spread of light
output is excellent (limited reduction in intensity) up to +/- 45 degrees from
axis; and that although intensity falls away beyond this angle, the PNI remains
clearly visible in most circumstances up to about +/- 80 degrees from axis
(this may depend on the manufacturer?). I don't know how this compares with the
technical specification and type approval requirements for these units. Due to
this wide angle of view - which is no doubt related to DfT requirements (for a
wide angle of viewing), alignment of the PNI at many junction sites is
extremely problematic without causing read-through to pedestrians using other
crossings - and this is being recognised as a serious issue in relation to Road
Safety design and audit.
1. After discussions with a local signal installation company about various
ways that we might overcome this problem, we have arranged for this company to
install a metal grid 'inside' some PNIs to act as a sort of louvre. This
'louvre' has the effect of restricting the viewing angle on 'only one side' of
the PNI. In effect the viewing angle is reduced down to +80 degrees through to
-45 degrees (i.e. we almost completely cut off about 35 degrees on one side).
The grid can be installed either way round - to restrict viewing to the left or
right hand side of the PNI. Whilst the brightness of the signal is unaffected,
the grid must affect the light output from the PNI due to the reduction in the
surface area of viewing (due to the metalwork in the grid).
2. The louvre is very effective in what it does, however restricting the
angle by 35 degrees in insufficient to overcome the orientation problems of
many PNIs. As a result we feel that although this technique is definitely
helpful, unless at alternative grid which further reduces the angle of viewing
from one side (down to say 10 or 20 degrees) could be produced for this
application - we will continue to have problems of PNI alignment at these sites.
3. Last week we invited Suku Phull of DfT to Sheffield to look at a typical
problem site. This clearly demonstrated the problems, and showed that the
device we had installed was effective in helping to overcome this problem -
even if it was not a total solution for these situations. I believe that Suku
now recognises this problem, and understands that the design of PNI for this
type of junction arrangement does need to be addressed. I also understand from
Suku that, on consideration of the issues, he has no problem with us continuing
with this trial as long as we continue to monitor the situation (I suspect that
this is NOT the same as saying that the trial has DfT approval). If other users
would like to try the same or a similar technique, I would suggest that you
contact Suku at DfT concerning this before proceeding (I would also be
interested to be kept informed - so that someone can be aware of how widespread
these problems are perceived to be).
4. I understand that there is an EITAC AG8 (signals) meeting today
(Wednesday) - involving DfT (Suku Phull); representatives of Siemens, PEEK,
TSUK (Microsense) and AGD; TCUG (and others?) - and that PNI issues are on the
Agenda for this meeting. I spoke to Peter Hutchinson (AGD) and Mark Pleydell
(TSUK - and Chair of this group) at length yesterday concerning these issues
and both are now well informed of the problems and the need to develop
solutions for users. I pointed out that retrofit solutions are likely to be
required at some sites - and this may influence the development of potential
solutions. I anticipate feedback from this meeting and any developments arising
in due course.
5. In discussion with AGD - who are the main source of these units (as I
understand that they supply PNIs for PEEK and Siemens under license) - we
explored possible ways forward. Two options are likely:-
a) Reducing the angle of view - symmetrically on axis - down to say 30
or 40 degrees overall (i.e. +/- 20 degrees from Axis)
b) Restricting the angle of view just on one side of the Axis (down to
say +80 / -10 degrees)
I can see advantages of either approach - but I feel my preference would be for
the latter - option 'b' (above) - but I would be interested to hear the views
of other users.
I understand that AGD are now positively looking at this issue in development -
and would like to adopt the approach of producing a unit to an Appendix of the
main specification for PNIs - to meet these specific requirements (for
junctions). The timescales for prototypes could apparently be weeks rather than
months (according to AGD).
6. My colleague David Key (who is currently on leave) and I have already
received a fair number of comments from users in other authorities with similar
problems on site. In order to take this matter forward (perhaps even 'push'
this forward?) - I would be interested in feedback from other users about the
issues raised above, whether they have similar problem sites (and if so, how
many PNIs may be affected) - and any preferences about options 'a' and 'b'
above. You can do this via this the TCUG list - or by direct e-mail as you
prefer.
Sorry for the long e-mail - but I hope you (or your Road Safety advisors?) have
found this information useful.
Regards
Howard Saffer
Traffic Signal Design Group
DEL - Development Services
Sheffield City Council
Tel: 0114 - 273 - 6154
Fax: 0114 - 273 - 6182
Mailto:howard.saffer@xxxxxxxxxxxxxxxx <mailto:howard.saffer@xxxxxxxxxxxxxxxx>
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