When overtaking a cyclist in Ireland, what minimum clearance should a bus driver allow where possible?

1. At least 2 metres at every speed, even if that requires crossing a solid line
2. About 0.5 metre at every speed because the cyclist uses a separate road space
3. At least 1 metre up to 50 km/h and 1.5 metres above 50 km/h
4. Exactly one bus-mirror width, provided the driver sounds the horn first