> This brings up smething that's been fascinating me. New Lynn here in
> Auckland looks like this (single track):
> During the day there is a DMU suburban service. At night there is a
> reasonably heavy freight service.
>
> When the freight service runs at night the Level crossing seems to be
> worked by track circuits in the usual way. However the DMU service runs
> somewhat differently.
>
> A down DMU approaches the station and stops at the platform. At that point
> the down signal is red and the LC barriers down. When the train is ready
> to leave it sounds the horn, the barriers drop and the signal clears.
> In the other direction, the up signal and the barriers seem to be
> controlled by track circuit.
>
> I presume that the signals (both 2 aspect) are only there to protect the
> level crossing. If they were there to add a section and increase capacity
> I would expect them to be at least 3 aspect since the rest of the signals
> I've seen on the line are 4 aspect. The location is not a passing place.
>
Correct. They are home signals to protect the level crossing. They cannot be cleared unless the level crossing has
been operating for a set peiod of time (usually about 15 seconds).
> I don't know where the signalling control centre is. but it's not within
> earshot. and I couldn't see any CCTV cameras.
> How does sounding the horn trigger the signal/Level crossing?
>
It does not. There must be someone who hears the horn and knows from that that the train is ready to depart and
starts the level crossing.
> Does this mean that the DMU service and freights can't share the tracks at
> the same time? The station is in a dip between two gradients so whichever
> way the freights were travelling they'd be stopping against the grade then
> starting against it again if they had to stop at the L/C.
The signal box would know whether the train is a through or a stopping train. Stopping trains would have the signal
against them and the level crossing up. Through trains would have the level crossing down and the signal cleared.
-- David Johnson CityRail Guard trainman@ozemail.com.au http://www.ozemail.com.au/~trainman