I haven't been on the Metrolink for a while, but remember seeing a sign at the G-Mex stop telling drivers to switch to 'street running mode without steps'. As well as speed limits, I seem to recall it has a different horn/whistle for road/off-road running. I also think the wing mirrors pop out for street running and the indicators are activated. And obviously the signalling is different on-street, I don't know if this has any impact on the tram's safety systems.
So I'm guessing that the change in mode engages/disengages all the various settings.