Re: Crossing lights 'flashing too long'

["HXP1" <hxp1@bigfoot.com>]

Rod Young <freight_man@hotmail.com> wrote in message
390eaa96$0$31520@news01.syd.optusnet.com.au">news:390eaa96$0$31520@news01.syd.optusnet.com.au...

> This new crossing [predictor] also saves time on open crossings, as a
> computer chip tests the train speed, on the approach and slows the boom
> activation down to match the speed of the train.

The predictor transmits a fixed current to the track, depending on the
distance to a short circuit between the rails, caused by either a train or
the terminal shunt, the voltage between the rails will vary.  This gives you
the distance to the train, and comparing this to time, speed can be
calculated. Then, depending on the programmed warning time, the output relay
of the predictor will operate if a train is more than xx seconds from the
crossing.  Simple really.

> This is a great idea, as our trains travel from 65 kph to 130 kph! NSW
> surely use a similar system, after all the xpt can do 160 kph there,

I know NSW bought a Safetran predictor as a prototype, have they stared
using them wholesale yet?

Victoria uses Harmon HXP's, Sth Australia & Tasmania have Safetran GCP's,
and AFAIK there are a handful of predictors in the Pilbara.  I'm not aware
of anywhere else using predictors though...

--
HXP1
(now with v6.08 software)