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