Reduced overlap

[PJW]

We were discussing the stepping up of warner routes today.
Is the only way of stepping up a warner to main by setting a route from the exit signal, or can the signaller overset the main route on top of the warner?

The quick answer is only by forward route setting.
If the Warning route is set then the Main is prevented from setting (think about it; on the Control Table for the (M) woute one of the entries is he associated (W) and (C ) are route normal.
Of course if the signal has not yet cleared the (W) route won't be approach locked and thus if signaller wanted to chnge their mind then could pull entrance button then push again and select the Main exit and achieves their aim.

If signal has already cleared then (in RRI at least) the step-up has to be prevented to avoid a brief aspect reversion; it is really of little significance anyway gven that the train will be almost at a stand about to pass the signal in rear- too late to be of any benefit.

The Western Region traditionally only had one class of route with the selection such as it was at aspect level. In this system the "Main" with a full overlap is the default, but a "Delayed Yellow" broadly equivalent to a "Warning" results if the full overlap is not available but the shorter overlap is. The signalleer can do this deliberately by keying some points to the conflicting position; they then always have the choice to move them to the full overlap position and they then become locked in that position and the aspect clears and effectively has become a "Main". Hence in this case it is a short of equivalent to step-up.