(29-08-2012, 05:30 PM)alexgoei Wrote: I would like to test if my understanding is correct by putting forward the following arguments:
1 Because a ABCL is almost identical to the AHBC (as far as motorists are concerned and this seems to be covered by the literature I have read), there does appear to be a requirement for trains not to arrive earlier than 27 secs at the level crossing.
2 As the person monitoring the correct operation of the crossing equipment is the driver and he must be able to see the crossing, DLCI from the SSRB (which must not be more than 600 metres from the DLCI in case any of the crossing equipment is not working),
this will in turn determine the crossing speed so that if all goes well he should arrive the crossing no less than 27 secs.
Am I correct?
Cheers
Alex
Certainly correct in that the ABCL is very similar in presentation to the motorist as an AHBC.
Also correct re method of operation of the crossing.
Also correct that the position of the SSRB is determined from the visibility constraint and that itself determines the crossing speed to the value for which there is sufficient distance to brake to a stand prior to the road.
Therefore I do not disagree with your argument, but the calculation does differ from the "27secs at linespeed" used for the AHBC (ignoring the other allowances for speedo error, equipment response time, skewness of crossing etc).
PJW