'Passive Safety' Outside the UK & Europe

[Debaser]

Not a technical question, just a general query as to whether 'passive safety' in roadside design is a purely European phenomenon (most discussions seem to centre around its implementation in the UK or Scandinavia) or if it is being used in North America or Australasia.

For those who don't recognise the term the following website gives a good starting point;

http://www.ukroads.org/passivesafety/

also;

http://www.ukroads.org/webfiles/Guidelines Print ready.pdf

Is this something that's intrinsic to your designs, or like Safety Audits perhaps, is it seen as giving an unneccessary opening to future litigation?

 

[ACtrafficengr]

I haven't heard anyone use the term in the US, but similar techniques have been used for years. For example, by January 17, 2013, all sign structures on roads with speed limits over 50 mph (80 km/h) must be out of the roadside clear zone or crashworthy ((breakaway, yielding, or shielded with a longitudinal barrier or crash cushion).

"...students of traffic are beginning to realize the false economy of mechanically controlled traffic, and hand work by trained officers will again prevail." - Wm. Phelps Eno, ca. 1928

 

[Debaser]

The term 'passive safety' seems to have been coined to differentiate it from the 'active safety' systems incorporated in vehicles (ABS, etc.).

I suspected such products would be in use, its just that one of them, a frangible sign post system, was actually dropped by its (US) manufacturer 3M with no further development/testing of differing size options.

http://www.fsp-ltd.com/about-us.html

It led me to wonder if there was some resistance to using this stuff or the ideas behind it.

 

[ACtrafficengr]

Reading the product specifications, only one thing ave me pause:

Care should be taken when handling the posts not to impart any undue impact (such as dropping the posts on the ground from height) as this may detrimentally affect the structural performance of the product.

I have to wonder how well they hold up to normal use and abuse.

Our signs take a significant amount of abuse from snow thrown by snowplows. Not so much the plows themselves, although they do occasionally damage signs and posts. Could they withstand the heavy wet snow/gravel/salt mixture that comes off the plow?

How about mowers? We've got about 7000 signs on our roads. I can't ask our maintenance crews to stop their tractors, get out, and use a nylon string trimmer because a post may break if they bump it with a mower.

Otherwise, if it were cost-competitive with standard breakaway steel posts, I wouldn't reject it.

"...students of traffic are beginning to realize the false economy of mechanically controlled traffic, and hand work by trained officers will again prevail." - Wm. Phelps Eno, ca. 1928

 

[Debaser]

Our maintenance can be fairly labour intensive, we're not above sending out gangs with strimmers to cut back vegetation even on motorway embankments, although that still doesn't guarantee there'll be no damage.

We're lucky in that the market for passive products is quite competitive and there's a wide choice of kit. The first link in the OP has lists of manufacturers/products which satisfy the BSEN requirements. In addition, certain manufacturers actually offer free replacement if their product has been damaged in a road traffic accident, which can bring whole life costs down considerably despite an initially large outlay.

Generally the split seems to be between material type vs. product design, that is traditional circular hollow section members made out of carbon fibre or some composite material (FSP, Jerol) versus traditional aluminium made into engineered structures (Lattix, Varley and Gulliver). Generally my only problem with the composites is that relatively small signs end up being mounted on 'tree trunks', i.e. large diameter posts, which looks very odd.