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Our Ref: 12s1420000
27 June 2012
Endeavour Energy
PO Box 6366
BLACKTOWN NSW 2148
Attention: Pat Woodbury
Dear Pat
RE: EXETER ROAD, EXETER - ROAD SAFETY REVIEW
GTA Consultants has been engaged by Endeavour Energy to review road safety issues in relation to the
location of three power poles recently installed along Exeter Road, approximately 3.8 kilometres north
of Exeter. The three non-frangible concrete power poles, known as poles 177, 178 and 179, have been
installed adjacent to the southbound traffic lane with a setback of approximately 1.5 metres. The new
power poles have replaced ageing timber poles that were located marginally closer to the roadway;
however the new power poles have a larger diameter and are more structurally significant. It is
understood that Wingecarribee Shire Council has raised safety concerns with respect to the size/ bulk
and location of the power poles to the Exeter Road travel lanes.
Exeter Road functions as an arterial road and links Exeter Village to the south, with the Illawarra
Highway to the north. The road is approximately 5.2 kilometres long and is a two-way road configured
with a 2-lane, 7.5 metre wide carriageway, set within a 20 metre wide road reserve (approx). Trees and
shrubs are located on both sides of the road within the road reserve and adjacent rural properties.
Exeter Road has a posted speed limit of 100km/h.
Exeter Road has a marked double barrier line (type BB) and edge lines in the vicinity with guide posts
provided at regular intervals; however no raised reflective pavement markers (RRPMs) are present. It is
noted that no passing opportunities are available along this section of Exeter Road.
Exeter Road is shown in Figure 1 and Figure 2, and the location of the power poles is shown in Figure 3.
Figure 1: Exeter Road (looking south)
Figure 2: Exeter Road (looking north)
Figure 3: Location of Power Poles
Power Poles
Source: Google Maps
Site Meeting and Options Assessment
GTA Consultants attended an on-site meeting on Thursday 14 June 2012 with representatives from
Endeavour Energy to better understand the localised road environment along this section of Exeter
Road, together with the safety concerns raised, and to discuss historical matters as they relate to the
power poles.
The site meeting also provided the opportunity to take on-site measurements of existing structures/
obstacles to inform the road safety review.
Clear Zones
GTA Consultants has reviewed the power pole locations with respect to Clear Zones for vehicles
travelling along Exeter Road in the vicinity of the power poles. The Guide to Road Design, Part 6:
Roadside Design, Safety and Barriers (Austroads, 2009) provides information relating to Clear Zone
requirements for various road environments and design speeds.
A steep batter is present, immediately adjacent to the road shoulder, along the north-west side of
Exeter Road in the vicinity of the power poles. The batter is estimated to be greater than 3:1 which,
according to the guide, cannot be safely traversed by cars and as such requires a clear run-out area at
the toe (bottom) of the slope. Since recovery (back onto the roadway) is less likely, fixed objects should
not be present in the vicinity of the toe of these slopes and a minimum clear run-out area of 3 metres
should be provided. As illustrated in Figure 4, at the toe of the existing batter there are is a row of large
pine trees which are located within the adjacent property and not within the road reserve. The presence
of these trees does not allow the above clear run-out area to be provided. The power poles have been
installed within the road batter approximately 1.5 metres from the edge of the travel lane. This places
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them within the clear zone for south-east bound vehicles travelling along Exeter Road and as such
requires treatment to minimise the severity of a vehicle collision.
Figure 4: Exeter Road (south-east bound)
Treatment Options
The Guide to Road Design outlines a number of possible treatments for poles located within a clear zone
in order to minimise the hazard presented by such poles. These treatments include the undergrounding
of cables, reducing the number of poles, relocating the poles, installation of frangible poles/ slip-base
poles and/ or road safety barriers.
As the power poles were recently installed, most of these treatment options are not practicable
(frangible poles/ slip base poles) or cost effective (undergrounding of cables) at this location. The
alternative to removing the hazard is to minimise the severity of a collision by way of installing a road
safety barrier.
Road safety barriers are defined in three types; flexible (wire rope), semi-rigid (w-beam and thrie-beam)
and rigid (concrete barrier). Each of these barrier types requires a reducing amount of deflection
capacity to operate effectively in protecting the hazard. Indicative deflection for different barrier types
is provided in Table 1.
Table 1:
Indicative deflection
Barrier Type
Indicative deflection caused by 2,000kg vehicle,
at 100km/h impacting at 25 degrees
Wire rope road safety barrier
1.7m-2.2m (depending on product type)
W-beam road safety barrier
1.4m
Thrie-beam road safety barrier
0.9m
Type F concrete barrier (permanent system)
0m
Source: Guide to Road Design – Part 6: Road Design, Safety and Barriers, Table 6.7
It is also noted that leading and trailing terminals (to prevent ‘head-on’ collisions with the barrier)
should be located at an appropriate distance from the hazard being protected and extend past the
point of need in both directions.
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Crash Data
GTA Consultants obtained vehicle crash data for Exeter Road within the vicinity of power poles 177, 178
and 179 from the Roads and Maritime Services (RMS). In the five years to 2011, no crashes were
recorded within 500 metres of the poles. It is noted that the previous timber poles were positioned
closer to the carriageway than the new concrete power poles, and as such, it could be argued that they
presented a greater road safety risk.
Figure 5 illustrates the crash history in the vicinity of the power poles over the five year period to 2011.
Figure 5: Reported Crash Data, 2006-2011
Power Poles
Source: RMS, Transport for NSW, Centre for Road Safety
Recommendation
On the basis of the above assessment and referencing general traffic safety and road design principles,
there is a clear road safety concern in relation to the location of the non-frangible concrete power poles
known as poles 177, 178 and 179 located on Exeter Road, north of Exeter Village. Even though the new
power poles are located further away from the road edge line than the ageing timber ones they
replaced, they are of a larger diameter and more structurally significant.
Given this, GTA Consultants would recommend installation of a w-beam road safety barrier to protect
the three power poles. It is recommended that the road safety barrier comprise a single continuous
span with transitions to a thrie-beam road safety barrier within the vicinity of the three poles. This is
due to the reduced deflection capacity between the power poles and the adjacent travel lane. Leading
and trailing terminals should also be installed as part of any road safety barrier treatment.
I trust the above clearly sets out our assessment. Naturally, should you have any questions or require
any further information, please do not hesitate to contact me in our Sydney office on (02) 8448 1800.
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Yours sincerely
GTA CONSULTANTS
Rhys Hazell
Senior Project Manager
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