central reservation

[dumbass]

whats the difference between the newly fitted wire central dividers and the old single rail divider

[sddsddean]

There are actually 3 sorts of barrier. TCB (Tensioned Corrugated Barrier), OBB (Open Box Beam) and TWB (Tensioned Wire Barrier).

TCB's are the most common. The barrier is tensioned using tensioning bolts every 250m (I think, trusting memory!) of the barriers length. The formula for tensioning the barrier is pretty lengthy and as it is temperature related you can quite often find the tensioning bolts are loose! The purpose of the posts is purely to hold the barrier 610mm above the edge of the road surface (thats why they are only 10mm bolts), but the 'strength' of the barrier is its continuity, so each 2.4 m section is bolted to the next with 8 16mm bolts. The barrier works by deforming around the car and thus 'holding on' to it to stop it rebounding into other traffic.

OBB's are used at structures and usually around signs and lights etc. They depend purely on their inherent strength (being like a rolled steel channel) and are often used in short lengths, though they can be extended by TCB if they have a strong anchor (eg the OBB is bolted to a bridge pier).

TWB work basically the same as a TCB, but they are much quicker to erect and repair as you don't have to undo and replace loads of nuts and bolts.

Whatever the barrier, they are really only effective with cars, as trucks and buses will go straight through them, but thats life!!

[ianess]

All 3 types are only really designed to stop cars, although in practice they can deflect larger vehicles and keep them in their correct side of the road.
Neither type is any good whatsoever for motorcyclists. I have a relative who has been left permanently disabled with terrible injuries caused by his striking a pole which was supporting the wire type of barrier. Being an optimist at least he reckons if the wire and pole hadn't stopped him he would have been thrown into the opposite carriageway with even worse results.
I believe that many motorycling organisations want more thought to be put into protecting bikers. Don't ask me how they can do it....as sddsddean says that's life but what's the alternative?