Introduction to Passive
Safety
Dave Auld
Graduate Engineer
Passive safety…..
• What is it and why is it important?
• How do passively safe structures perform in a
collision?
• Costs
• Deciding when passively safe structures are required
• Other roadside features to consider
What is passive safety?
•
Passive safety is the concept of designing as safe a roadside environment as
possible in order to reduce the severity of collisions involving errant vehicles.
•
Approximately one in five of all fatal or serious injuries are associated with an
unforgiving roadside environment.
•
Passively safe street furniture is specifically designed, and proven through
testing, to provide less resistance during impact and avoid sudden
decelerations which might result in injury to vehicle occupants.
•
First passively safe structures developed in Scandinavia in late 1980s.
Available in the UK from around 1995.
Why is it important?
•
Highways Act (1980)
Local Authorities have a duty of care to aid the safe passage of traffic on the
highway.
•
Road Death Investigation Manual 2007
Road death = unlawful killing until proven otherwise
As depth of investigations has increased, highways infrastructure has attracted
greater scrutiny.
‘The layout of a road, its associated facilities and features and its state of
maintenance/repair can all be contributory to the occurrence and severity of a road traffic
collision……The performance of a highway authority responsible for the road where a
collision has taken place is a vital consideration during such investigations…’
What structures are ‘deemed to comply’?
•
Steel posts of up to 89mm diameter, with a wall
thickness of up to 3.2mm, are classified as
passively safe.
•
Where post sizes exceed these measurements,
a passively safe product or material should be
considered, especially where the speed limit
is 50mph or over.
60mph crash test with 114mm post
How do passively safe supports perform in a
collision?
Category HE Supports
(mainly for tall supports)
Category LE Supports
Category NE Supports
Costs
•
Sign posts approx 3 x more expensive, light columns approx 2 x more expensive
than traditional steel equivalents, but…........
•
Longer, maintenance-free lifespan than conventional posts. Corrosion Resistant.
•
Using passively safe structures may negate the need for a safety barrier.
•
Designing Safer Roadsides – A Handbook for Highway Engineers (published
2008):
“Protecting a small/medium sized conventional sign supported by steel posts with
45 metres of safety fencing (including providing a suitable energy absorbing end
terminal) can cost about £5,000. The cost of using passively safe signposts for the
same sign could be between about £2,000 and £4,000 for one or two Lattix posts,
giving a potential overall saving of between £1,000 and £3,000.”
Deciding when to use passively safe structures
•
•
•
Is it necessary?
Can it be installed passively safe?
Can it be protected by vehicle restraint barrier?
•
Passively safe equipment should be installed
Signs &
Lighting
Columns
Stone/brick gateway structures
often used to signal entry into a
village or traffic calmed area.
Consequences of a collision likely
Broadly two passively safe types to
to be severe for occupants of a
choose from – aluminium and composite.
vehicle or a motorcyclist.
NYCC
Stone
Passive Safety Protocol
Motorcycles
gateways
Key Challenges
Even passively safe street furniture is
Approximately 900 KSIs per year in single
likely to cause serious injury or death if hit
vehicle collisions with trees in Great Britain.
by a motorcyclist, even at modest speeds.
Vehicles can be protected from impacts
Products such as Biker Mate and
with trees at high risk locations by
Bike Guard developed to protect
TreeFend.
motorcyclists in low to moderate
speed impacts.
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Trees
What products are available?
Aluminium
•E.g. Lattix. Energy absorbent lattice construction
•Designed to progressively crumple upon impact
then shear at the footplate.
•Recyclable and less prone to corrosion.
Composite
•Inner layer of glass reinforced plastic and outer layer of
polyurethane plastic. Injected with polyester resin for strength.
•Significantly lighter than steel and aluminium equivalents
•Maintenance free and corrosion resistant - marketed as having a
lifespan of over 60 years.
Signs &
Lighting
Columns
Stone/brick gateway structures
often used to signal entry into a
village or traffic calmed area.
Consequences of a collision likely
Broadly two passively safe types to
to be severe for occupants of a
choose from – aluminium and composite.
vehicle or a motorcyclist.
NYCC
Stone
Passive Safety Protocol
Motorcycles
gateways
Key Challenges
Even passively safe street furniture is
Approximately 900 KSIs per year in single
likely to cause serious injury or death if hit
vehicle collisions with trees in Great Britain.
by a motorcyclist, even at modest speeds.
Vehicles can be protected from impacts
Products such as Biker Mate and
with trees at high risk locations by
Bike Guard developed to protect
TreeFend.
motorcyclists in low to moderate
speed impacts.
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Trees
Protocol in Action Signposts
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QUESTIONS?
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