Senin, 15 April 2013

RE: [CanPassRail] PTC was Perceived Risk on Various Modes

 

Knot, your conclusion that there are only 10 seconds to clear the crossing
appears to be based on an assumption that there will be exit gates operating
at the same time as the gates at the entrance to the crossing. These are not
common, but when they exist they operate later than the entrance gates. So
any vehicle already on the crossing has 20 seconds to clear (actually 22
seconds since there should always be a minimum of 10% extra time built in).

The Canadian technical standard RTD 10 will give the actual requirements.
Try http://www.tc.gc.ca/eng/railsafety/rtd10-805.htm or
http://www.tc.gc.ca/media/documents/railsafety/StdErv12.pdf.

The standard doesn't discuss how the 20 seconds were determined. In 30 years
working with crossings I never thought to inquire into the details. However
I gained the impression it was more or less empirical, and the 20 second
standard was effectively reverse-engineered through trial and error.

Don Thomas

-----Original Message-----
From: Canadian-Passenger-Rail@yahoogroups.com
[mailto:Canadian-Passenger-Rail@yahoogroups.com] On Behalf Of Knut
Sent: April-15-13 11:40 AM
To: Canadian-Passenger-Rail@yahoogroups.com
Subject: Re: [CanPassRail] PTC was Perceived Risk on Various Modes

A nice presentation on the subject matter here with lots of statistics but
not a word how the 20 second interval was originally determined.

http://www.google.ca/url?q=http://www.techtransfer.berkeley.edu/railroad06do
wnloads/nizam_macdonald.pdf&sa=U&ei=ejdsUZ_kNeXI0wHes4CgCQ&ved=0CCUQFjAD&usg
=AFQjCNG9Wt-O34aBylfQAemV8ZSnVopmbg

The interval is actually a lot shorter - the gates need to be fully down
minimum of 5 seconds before the train arrives and of course it takes time to
lower the gates - so the real interval to clear the crossing is closer to 10
seconds after the warning signals get activated.

Knut

-------------------

On 2013-04-15, at 1:14 PM, Knut wrote:

> My understanding is that the 20 second time is the minimum elapsed time
between the activation of the warning signals at the crossing and the
arrival of the train at the crossing.
>
> Part of that time interval is the required time for a slow moving vehicle
to cross and clear the crossing if it can't be safely stopped before the
crossing.
>
> The longer the vehicle (an the slower it travels), the longer it will take
to clear the crossing, so if the 20 second interval was determined to be the
minimum required for an "x" foot long vehicle, wouldn't that time need to be
increased if the vehicle is now "2x" feet long for instance?
>
> The other factor that plays a role is the condition of the pavement of the
crossing itself.
> Some of these railroad crossings are in such poor shape that everyone just
crawls across it, heavy trail trucks even slower than cars.
>
> I have read about the 20 second interval in various places on the net but
have not found any resource that details how that interval was determined in
the first place and when.
>
> Knut
>
> ----------
>
> On 2013-04-15, at 2:31 AM, Don Thomas wrote:
>
> > The 20 seconds itself does not need to be reviewed (as per Knot's
> > comment on a subsequent post). It is the amount (if any) of
> > additional time which must be reviewed if there is a change in the
> > design vehicle.
> >
>
> [Non-text portions of this message have been removed]
>
>

[Non-text portions of this message have been removed]

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