Minggu, 14 April 2013

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

 

The truck in the British Rail accident had a police escort and they didn't
do their job. Their job was to contact the railway authorities to determine
the amount of warning time and arrange for a time when the truck could cross
safely. Warning signals are not supposed to be set up for such slow special
movements crossing the track. If they were, the signals would have to start
operating several minutes before the arrival of a train, unnecessarily
inconveniencing road traffic and encouraging drivers to ignore the signals.

Every crossing should have a "design vehicle" which is the longest, slowest
vehicle normally expected to operate across it. The design vehicle plus the
number of tracks (which affects crossing time) can be used to determine if
extra signal operating time is required. The standard operating time is 20
seconds plus an additional 10 percent for 22 seconds. Slow vehicles,
excessive grades etc can require additional time. Constant Warning Time
devices are used to ensure consistent warning time when train speeds vary
significantly. 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.

If there must be interconnection to pre-empt adjacent traffic lights or
operate advance warning lights, the circuits must be triggered before the
crossing signals themselves start operating (as James noted below).

From: Canadian-Passenger-Rail@yahoogroups.com
[mailto:Canadian-Passenger-Rail@yahoogroups.com] On Behalf Of midrly
Sent: April-14-13 8:43 PM
To: Canadian-Passenger-Rail@yahoogroups.com
Subject: Re: [CanPassRail] PTC was Perceived Risk on Various Modes

Consider a heavy vehicle or school bus stopped for a public crossing and
then proceeding over it slowly. Even with twenty seconds' warning, it is
possible for a train to strike that vehicle when it is is in the process of
crossing the track.

This is not a new issue. In 1968, a British Rail passenger train struck a
truck loaded with a transformer on a level crossing that had just received
automatic warning devices--

http://www.railwaysarchive.co.uk/docsummary.php?docID=74

Although this partly was a result of the trailer moving slowly over the
crossing, the TSB has alluded in a report of theirs to there not being
enough warning to long vehicles to allow them to clear the crossing. Just
about every truck trailer is 53' long nowadays, and two of the these
trailers are hauled behind a tractor between Toronto and Montreal. Unless
these truck trains do not pass over ANY public crossings, the danger is
patently obvious given the requisite 20 second warning for automatic
crossing protection. If Highway 401 is closed for any reason, these truck
trains have to use the EDR routes over public crossings.

In November, 1994, a VIA train struck a truck on a level crossing in
Quebec--

http://www.tsb.gc.ca/eng/rapports-reports/rail/1994/r94d0191/r94d0191.asp

Both of these involved transport trucks. But even scarier to me is the
prospect of a school bus stopping per the law at a public crossing, then
accelerating over the crossing and being struck by a train that has happened
on the crossing circuit just as the bus fouls it.

Or on an unprotected crossing at the foot of a hill over which the
approaching train gives the required twenty seconds' 14L whistle signal
which is not enough time for an accelerating school bus to clear it. One of
these crossings is on a shortline two blocks from my house--and a school bus
uses it on weekday mornings.

Steve Lucas.

--- In Canadian-Passenger-Rail@yahoogroups.com
<mailto:Canadian-Passenger-Rail%40yahoogroups.com> , "James"
<unionrouting@...> wrote:
> The problem with that approach is in determining if the vehicle is
actually stuck on the tracks, or if is just passing over them. Even then,
>
> Consider that in North America, the crossing circuits are set to operate
for only 25 seconds or so. (20 seconds is the legally required minimum) In
some cases, where there is a traffic signal preemption at nearby
intersections, the crossing circuits might activate up to 45 seconds ahead
of the trains' arrival at the crossing.
>
> Consider also that a semi truck might take five or ten seconds to
completely clear a crossing at low speed. That means, if the truck is just
starting past the crossing signal when it begins to function, it might still
be occupying the tracks only 10 or 20 seconds before the arrival of the
train, under current designs. If you can see ahead from the train, such as
while riding in the dome car, you will frequently see cars and trucks
driving across the tracks only a short distance ahead of the train.

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

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