Re: Signalling Questions in Brisbane?

[Eddie Oliver <eoliver@efs.mq.edu.au>]

pdwyer wrote:

> 
> It seems to have spread ;) It is not an inherently dangerous
> practice, the circuit design for the flashing is designed to
> fail safe, that is the next most restrictive aspect. That's why
> the Flashing yellows are just above the Red, sequence wise.

Please elucidate. The logic of the above is not clear.

QR is one of the very few systems in the world where the flashing yellow
aspect is MORE restrictive than the steady one. In most systems, because
of the very argument that you have raised, flashing or pulsating aspects
are less restrictive than steady ones - because if the flashing fails,
the resulting steady aspect is more restrictive and the situation is
thus failsafe.

Presumably if a QR flashing yellow fails to flash, the signal has to
default to red. This requires proving that the flashing is operative. If
someone else's flashing or pulsating yellow fails to flash/pulsate, it's
no big deal.

Eddie Oliver