Bridge spins slippery web

The brand new non-slip surface recently applied to Webb Bridge over the Yarra in Docklands proved to be anything but when it re-opened.

Several riders suffered injuries when they hit the deck on the freshly re-surfaced bike and pedestrian crossing.

The bridge had just opened after a lengthy closure for treatment of the concrete surface.

It was a typically damp Melbourne Spring day when the riders, apparently evading pedestrians that had loomed ahead in the bike rather than in the pedestrian zone, found their wheels suddenly losing adhesion.

The crashes came as a shock to the City of Melbourne and to the engineers, contractors and materials suppliers retained to repair the bridge deck.

They had assumed that the non-slip label on the can meant what it said.

The City, quite properly concerned at the slippery non-slip surface, commissioned an independent investigation immediately.

The test confirmed the label was right: the surface was indeed non-slip and its grip exceeded the required standard by some margin.

What gives?

Further inquiries are being made so any further comments at this stage would be speculation.

So let’s speculate a little, in the interests of rider safety.

Over the years several similar phenomena have been reported to Bicycle Network: non-slip surface treatments freshy applied to roads and decks have mysteriously been slippery for bike tyres.

But only soon after application, possibly before complete curing, and only when conditions were damp.

Some witnesses reported a thin, oily emulsion over the surface in these earlier instances.

But that is basically where the knowledge stops. Nobody knows.

We are hopeful someone will work it out one day. In the meantime, when riding over anything that looks very recently applied, on a wet day, be careful.

In a welcome response the City has commissioned a safety audit of the bridge. One issue sure to be looked at is what measures are available to encourage more predictable movement by pedestrians.

And why was the bridge being re-surfaced anyway? For the good reason the concrete decking was cracking a little and water was at risk off penetrating and causing permanent damage.

The new coating is to seal the deck, keep the elements out, and keep the bridge healthy for years to come.

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