Background

There seems to be more "fear, uncertainty and doubt" (FUD) than published research on wire rope barriers and the relationship to motorcyclists. I did a quick search or the internet and found no scientific basis for motorcyclists to prefer the wire rope barrier over the more common W-beam guardrail.

One manufacturer states that their wire rope barrier has been fully crash tested to the latest CEN European standards. I am not aware of how motorcyclists were simulated in such crash testing.

I looked a a wire rope barrier along Gorge Road, Athelstone, SA. The wire rope in the barrier consists of four ropes, each 19mm in diameter. The strands making up the wire rope are much coarser than those in 4 wheel drive winch cable. The top two ropes are threaded through a hole near the top of the supporting posts. The lower two ropes seem to be held in place because they criss-cross between the posts and are supported vertically by small plastic pegs on the posts. The posts have an "S" shaped cross section and present a rounded or blunt edge (compared to the posts used with the W-Beam guard rail). Posts appear to be about 2 metres apart. Wire rope is under tension with no apparent freeplay. The top rope is about 600mm above ground level and the lower ropes are about 500mm above ground level.

Consider this - motor vehicle seat belts are about 47mm wide - and there is no cause for concern about a cheese cutter effect. The pattern of the wire ropes indicates that a motorcyclist impact would be absorbed by three of the four cables. This would distribute impact force at least as well as a vehicle seat belt - with an effective width of (3 X 19mm) 57mm plus the additional distributing effect of the 100mm separation between the upper and lower wire ropes. Three wire ropes should therefore distribute the force better than a vehicle seat belt. If vehicle seatbelts have negligible "cheese wire" effect. then four-wire-Rope Barriers should also have negligible "cheese cuter wire" effect.

W-Beam guardrail is the most widely accepted, cost-effective highway safety barrier in the world. From a motorcyclists perspective, this type of guardrail is not effective at gradually slowing an impacting rider or motorcycle. The W-Beam guardrails are stiff and spread the impact load amongst the nearby posts. The Wire Rope on the other hand will put more load on the closest post. Considering the mass of the motorcycle and/or passenger, I expect that the wire rope barrier would would absorb the impact (and slow the rider) better than the less flexible W-Beam guardrail. I recall the punch line "it's not the fall that hurts, but the sudden stop at the end". Sudden deceleration of a person's head can result in brain damage as it crashes against the inside of the skull.

The guardrail posts are an important factor. The "C" channel posts of the W-Beam guardrail presents a rounded side in one direction, while the opposite direction presents the sharp edges of the channel. Impacts sometimes occur on the far side of the road - where the "C" channel posts present sharp edges. The guard rail itself, has sharp edges top and bottom.

From my brief investigations, I believe that a 4 Wire Rope Barrier is an improvement over W-Beam guardrail, from the motorcyclists point of view. I would like to see a scientific comparison. The concrete block pendulum is used in vehicle side impact tests. Perhaps this principle could be used with a rope tied high above the guard rail, a bag tied to the free end of the rope and a pumpkin inserted in the bag. Allow the pumpkin pendulum to crash test the pumpkin(s) to see which type of barrier is friendlier to pumpkin impacts.