WIRE ROPE SAFETY FENCE
REFERENCE ARTICLES
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BRIFEN FENCE OUTPERFORMS ALL EXPECTATIONS |
The performance of the remarkable Brifen Wire Rope Safety Fence was proven again
recently after a major impact by a fully-laden semi trailer, travelling at an estimated 100 kph along the Hume
Highway to the north of the New South Wales regional centre of Goulburn, some 200km from Sydney. Experts from the
NSW Roads and Traffic Authority (RTA) and Police Department have praised the performance of the fence, crediting
it with the prevention of what they believe would have otherwise been an horrific accident.
Even after being impacted by a fully-laden Scania semi-trailer 'Pan Tech',
this section of the Brifen Wire Rope Safety Fence on the Hume Highway, some 10km north of Goulburn, prevented the
semi-trailer from crossing into the path of oncoming traffic thus avoiding a potential multiple vehicular impact
disaster.
There was no serious injury to the driver and only minimal damage to
the semi-trailer. Travelling at an estimated 100kph at the time of impact, a total of 297 collapsible Brifen WRSF
posts were damaged along two fence sections measuring nearly 360metres.
Largest Recorded Impact with Brifen WRSF
The Hume Highway impact, which occurred in the early morning hours of Friday September 12th, is the largest recorded
impact with any Brifen Wire Rope Safety Fence anywhere in the world. The Scania Semi-Trailer "Pan Tech"
was travelling between Melbourne and Sydney when it impacted with the 4-wire fence, located on a downhill gradient
some 10km north of Goulburn. Damaging a total of 297 collapsible fence posts, over two fence sections measuring
nearly 360 metres, it appears that the severity of the damage was due to the vehicle travelling approximately 250
metres after the initial impact before the brakes were applied. Such was the severity of the impact that it even
resulted in some minor damage to the wire rope and several rope fittings.
Even after being exposed to the massive forces involved with a loaded semi-trailer impacting the fence at 100 kph,
the Brifen fence only allowed a maximum deflection of approx 3m , and importantly, despite the vehicles high centre
of gravity, prevented the semi-trailer from rolling or tipping.
In the past 25 years since Brief fences were first introduced, the previous three largest impacts were; damage
to 72 posts after a semi-trailer impact along the M62 in England in 1991; damage to 62 posts after an impact by
an unknown vehicle on the M4 in Sydney in 1995; and an impact involving a truck and trailer which occurred along
the Auckland Motorway in New Zealand in 1994, resulting in damage to a total of 48 fence posts.
Proven Performance in Multiple Impacts
As the major transport link between Melbourne, Canberra and Sydney, the Hume Highway forms the axis of Australia's
south-east inland road network. The combination of dual high-speed carriageway, high traffic flows and narrow painted
median (with an approximate width of only 2.4m), resulted in the selection of Brifen to prevent vehicles crossing
the median and travelling into the path of oncoming traffic. To cope with the narrow median, the Hume Highway installation
incorporates a design modification that reduces the spacing between the collapsible posts to 1.2m, rather than
the standard spacing of 2.4m.
This reduction in post spacing further reduces the distance that a vehicle would travel past the fence installation
line after impact, without any reduction in the performance characteristics of the fence. Since the installation
of the Brifen fences along this section of the Hume Highway some 12 months ago, they have been impacted on numerous
occasions. On each occasion, the Brifen fence performed perfectly, preventing the vehicles from crossing into the
opposing traffic lanes and bringing them safely to a stop. As with impacts in all Brifen locations throughout Australia,
and indeed around the world, none of the impacts along the Hume Highway fences have resulted in any serious injury
or death.
Fence Design the Key to Success
Even though Brifen fence was not specifically designed to restrain truck and heavy vehicles, the fences have an
excellent record of performance during many heavy vehicle impacts around the world. By absorbing the energy of
the impact with minimal fence deflection, Brifen WRSF prevents the errant vehicles from rolling or crossing into
the opposing traffic lanes, effectively "catching" the vehicle and guiding it to a stop, with minimal
damage to the vehicle and no serious injuries to the vehicle occupants.
The key to success in the design, which is the result of many years of development work, combined with well in
excess of 20 full-scale crash tests in conjunction with MIRA and the UK Department of Transport.
Test Results
As a result of the tests, Brifen design engineers discovered that only by utilising a unique (and now patented)
4-wire 'woven' rope design, could the fence deflection be minimised to a safe and acceptable level. So important
was this 'woven' rope design development, that tests between two full length (626m) sections of the fence, impacted
at an angle of 20 degrees by a 1500kg vehicle travelling at 113kph, demonstrated a reduction in deflection to less
than 1.5m, compared to old 2x2 parallel rope system. Continued testing revealed the fence deflections during impact
could be further reduced to between 1.2 and 1.3m (for the same impact criteria) by reducing the post spacing to
1.2m from the standard 2.4m, which provides an ideal solution for narrow median situations such as that found along
the Hume Highway installations.
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