Wednesday, September 02, 2009

take me home, country roads

My mention of the M50 in the Go Ape! post leads me to the ridiculously comprehensive road information websites CBRD and SABRE, both of which have interesting things to say about junction 3 of the M50 (otherwise known, slightly more grandly, as the Linton Interchange), where we got off to head for Parkend. SABRE calls it "arguably the lowest-standard motorway junction in England" and CBRD includes it in its collection of Bad Junctions. Sure enough it is pretty hair-raising, particularly to the uninitiated - heading west as we were you get a shortish deceleration lane before a 90-degree bend through a gap in the hedge and then another 90-degree bend almost immediately. Judicious use of the handbrake may be required at this point. It'd be a death trap if the M50 wasn't one of the quietest motorways in Britain (junction 1 which we also negotiated on Monday isn't a lot better). It's all a legacy of the M50 being one of the oldest motorways in Britain - it was mostly finished in 1960.

View Larger Map

My nomination for the Bad Junctions page is a bit more controversial, but as I have to negotiate it every morning I think I'm qualified to complain about it. It's the south-western corner of the Almondsbury Interchange. Now of course the Almondsbury Interchange is a poster-child for good junction design, and I have no argument with that in principle. The trouble is the purity of the junction itself (J20 of the M4, junction 15 of the M5) is ruined by having junction 16 of the M5 only a couple of hundred yards away. So if, for instance, you're coming off the eastbound M4 (as I am every morning) and want to get off at junction 16 for the business parks at Aztec West and Almondsbury, you have to cut across all the traffic coming off the westbound M4 and wanting to get onto the southbound M5. Similarly if you're coming off the northbound M5 to get onto the westbound M4 you're in conflict with the traffic coming on at junction 16 and wanting to immediately either get on the northbound M5 or the eastbound M4. This conflict between entering and exiting traffic at adjacent junctions is called "weaving" and is generally considered a Bad Thing. I have no suggestions as to how J16 could be improved, just pointless griping. I hope that's clear.

No comments: