Wednesday, April 12, 2006

The Road Glass Mystery

Glass - It seems to be everywhere on London cycle lanes. With the assistance of road camber sloping towards drains, broken glass gets swept by the air currents of fast moving cars, in to cycle lanes. Where did it come from? And what can you do about it?

Types of Glass

  • Smashed bottles
  • Shards from car crashes
  • Smashed car windows, theft from cars
  • Tiny millimetre sized sharp glass pieces, hard to spot.


The 1st line of defence has to be avoiding riding through broken glass, but that's often not an option, especially with the millimetre sized glass.

2nd line of defence is a proven brand of tyre, with a specific anti-puncture design or guarantee.

The 3rd line of defence I've found to be pre-emptive maintenance after every ride. Religiously fingertip checking each tyre for any embedded glass, it only takes a few seconds.

Sometimes an embedded piece of glass can stay in a tyre for a while, awaiting the final incision through the inner tune, at a time least convenient to you.

Sods Law

The omnipresent Monsieur Sod is not a nice man, and punctures fall within his scope of activities. Likely scenarios Mr Sod prefers:

  • It's raining.
  • You're late anyway, then you get a puncture to make you REALLY late!
  • Your ride passes through a posh area, a suburban area, and a high-crime sh*thole. Guess where you're gonna get your puncture?
  • All of the above combined!

Puncture info here.


Where does all this glass come from???

Pub carelessness and drunken glass smashing is definitely a factor.

Perhaps the rock salt winter gritting lorries contain some unintended glass, but that still doesn't explain it in the summer...

Curiously "glass grit" is blasted at high pressure for cleaning purposes, e.g. graffiti removal, or stone cleaning. This could be another potential source.

Also, White line road markings include glass beads on the white line surface - for reflective qualities. Could this be a source?

Clean Sweep

And to think the solution is as simple as a day's road sweeping every now & then, to maintain arterial cycling routes in your local area.

We're not talking big costs either:
A big road sweeper to hire, is around £300 for a day.
A little road sweeper to hire, is around £45 for a day.

It is not inconceivable, that during just one 8 hour day, of solely driving around, a sweeper could easily cover all the main cycling routes in your area. Good value for money if you ask me.

But when was the last time you saw a road sweeper?

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1 comment:

Karl McCracken said...

I also use SLIME in my tyres. It's not a complete puncture-proofing solution, but in general it'll slow the air leak down enough to get you out of the high crime area, and back to the nice civilised streets, where like as not someone'll offer to help (and not nick your bike / case as soon as your back's turned), while one of their neighbours makes you a nice cup of tea (with some home-made biscuits). If you live near Utopia, that is!

Seriously, the SLIME's a pretty good fall-back though.

And I like your analysis of the costs of street sweeping. If councils are serious about getting more people out of their cars, this seems like a pretty low cost.

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