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[email protected] · April 19th 17, 09:14 PM posted to uk.transport.london

In article , (Alan Grayer)
wrote:

On 19/04/2017 13:47, d wrote:
On Wed, 19 Apr 2017 11:28:08 +0100
Roland Perry wrote:
In message , at 16:07:44
If you cycled in Cambridge you would have noticed a year or more ago.

I'll look more carefully next time I walk.

On a related cambridge note - why do some parts of the "guided" busway
not have guiderails? I don't mean the bits that cross other roads, I'm
talking about segregated sections such as the bit in Orchard Park? I'm
struggling to see the logic.

My understanding is that the guidance system is designed for
high-speed running on large-radius curves (i.e. on an old railway
alignment), and does not cope safely with curves below a certain
radius. In order to fit around the Orchard Park devlopment, that
section of busway has a bend which is too tight for guidance. It
doesn't matter, as that section is low-speed, and only a short
distance between the junction with the main busway and the point at
which the busway ends. At both of those points the driver has to take
over the steering anyway, so doing so between them is no great matter.

The exception on the Orchard Park section is the stops and a short eastbound
section near Histon Road. They were built with true guideway sections. All
newer guidance is by steel strips on flat road surfaces.

The only other significant unguided segregated section I am aware of
is the new piece between Milton Road and Cambridge North Station.
This doesn't have sharp bends, but again is short and low-speed. I
would guess that cost was the deciding factor there.

This is probably true but the unguided section at Orchard Park probably and
the approach section to Cambridge North station definitely are unguided on
cost grounds.

The guideway track sections were cast at a concrete factory set up specially
for the purpose at (I think) Longstanton. Once the sections were made it was
demolished and the site is now a park and ride car park. So the cost of
making new guideway sections would be prohibitive and that's before you talk
about getting the special laying machine back on site. I'm not even sure
what happened to that.

None of the Cambridgeshire kit was used for the Luton busway which has
shorter track sections which can be laid by mobile crane. They probably
don't have a track section casting capability at Luton any more either.

--
Colin Rosenstiel