 Clearances for bridges
On Jul 17, 6:17 pm, billetelic_ferroequinolog...@m wrote:
> On Jul 17, 4:39 pm, Michael Bell <mich...@beaverbell.co.uk> wrote:
>
> > What are the clearances for bridges and suchlike and for the boundary
> > fence? Looking at the fences I get the feeling that there is some
> > leeway!
>
> > Michael Bell
>
> > --
>
> There are two separate issues to be considered here. The clearances
> for bridges are related to the structure gauge and, on top of that,
> the Design Kinematic Envelope, which represents an additional
> clearance beyond the structure gauge to allow for movement of the
> vehicle. The DKE varies according to linespeed and (ICBW here) type of
> vehicle.
>
> Historically, the boundary fence marked the limit of railway land
> ownership, which can stretch beyond the tracks themselves, eg to the
> top of a cutting or the bottom of an embankment. Furthermore, on new
> railways, the boundary fence should, wherever possible, allow staff
> working on the line under what are known as "Red Zone" conditions to
> be able to reach a position of safety (defined as 1.25 m from the
> nearest rail for linespeeds of up to 100 mph and 2 m from the nearest
> rail for linespeeds 101-125 mph in the Personal Track Safety
> Handbook).
>
> The PTS Handbook defines a Green
(Sorry - hit the wrong key!)
Zone as a zone of work where one of the following conditions applies:
1. All lines blocked to traffic (Safeguarded Green Zone)
2. Worksite separated from running line by temporary fencing (Fenced
Green Zone). The distances vary by linespeed and according to what
type of fence is in use.
3. Worksite at least 2 m from the running line (if supervised) or 3 m
from the running line if unsupervised (Separated Green Zone).
If these conditions cannot be met, Red Zone rules apply and lookouts
must be used. There are many areas on the railway where Red Zone
working is not permitted owing to restricted sightlines, clearances
etc. For example, there are signs on the boundary fence south of
Hitchin on the Down side stating "Red Zone Prohibited".
So in an ideal world, the boundary fence will be so located to allow
at best a separated Green Zone to be provided or at least a position
of safety under Red Zone working.
HTH. |