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FlipC blogged today over on The Mad Ranter about potholes, misplaced grids, and his weekend and I wanted to add a note about the pothole on Milton Road, at the junction with Arbury Road and Union Lane.

On the town-bound side of the road the bus lane helpfully disappears to be replaced by an advisory cycle lane for the few metres until the traffic lights. In this advisory cycle lane there is an 80cm square tarmac patch added to cover some roadworks done years ago. After increasingly bad subsidence the patch was dug up and refilled, but as is so often the case the edges weren't coated with tar to stop cracks forming, so the tail edge of the replacement patch started chipping away the same week it was laid. This soon turned into a hole about 10cm long and similarly deep, on the order of being a wheel-breaker. They've since patched the patch but the new tarmac sticks up above the road surface, still by enough to make you swerve towards the kerb to avoid it. Who can say how long this will go on for?

Already I hear you wondering how this can be. If bikes really generate so much less wear on the road surface than heavier vehicles, how does even a substandard patch wear out so quickly? The answer is obvious to anyone who's used the junction or seen it at a busy time, and if I had more faith in the competence of road designers, I would say that any professional should be able to guess after seeing the road layout.

After the bus lane disappears the road starts to narrow, so approaching the junction we have one slightly wide all-vehicles lane and a not-particularly-wide cycle lane. Turning right is not prohibited, so when the lights turn green, often there will be one or two cars rolling over the stop line to wait in the middle of the junction. Because the carriageway is just wide enough, the vehicles that don't want to turn right will pass on their left, which requires entering the cycle lane (often without first checking for the presence of cyclists), and driving over the dodgy bit of tarmac, doing damage roughly proportional to the fourth power of the axle weight, and generating the above-mentioned pothole.

It's not all bad news, though. Thanks to Clare on the Cambridge Cycling Campaign members' mailing list, I heard that the junction of Union Lane and Chesterton High Street had been resurfaced. On Friday I happened to go that way to the Waterbeach cycle path, which is part of Route 11 on the National Cycle Network. The junction sported a large hole in the middle of the carriageway, caused by heavy vehicles turning right onto Chesterton High Street across an untarred seam in the road surface. There had been a series of patches over it, but they were all a bit half-assed and came loose after a few weeks. Now, the whole junction has been resurfaced, so the hole is gone for good.