As for the W-class trams performing "quite admirably", the ones in service (W6) are underpowered going up slight hills, and they do not have
Fortunately Melbourne W trams now in service have had track brakes fitted to them. I understand they are electromagnetic and forcibly clamp down onto the track to quickly bring the tram to a halt.
You're right. I hadn't noticed that the City Circle trams have had track brakes fitted. The brakes are largely obscured by the under-bogie
brackets required to hold them in place. I don't know how recent
that is, nor have I been down to Chapel Street lately to see whether
those trams have had the same treatment.
This matter reminded me of the runaway tram in Swanston Street in the mid-1970s. A truck collided with a south-bound tram outside the CUB building and demolished the driver's cabin. The driver was stunned,
and the tram gathered speed down the incline. Passengers jumped off
the tram as it gathered speed. The conductor had to rush to the
rear of the tram to apply the handbrake, but did not bring the car
to a halt until it had nearly reached La Trobe Street.