Final answer:
When pulling out from a bus bay, yield to all traffic and flash your left turn signals before merging with caution.
Step-by-step explanation:
When pulling out from a bus bay, the correct protocol is to yield to all other traffic. This means you must wait until it is safe to merge with the flow of traffic, without forcing other drivers to slow down or change lanes to accommodate your bus merging. Flashing your left turn signals and cautiously pulling out is also a sensible practice to alert other drivers about your intentions, but it must be done while ensuring you do not disrupt the existing traffic flow. It's important to note that sounding your horn is not a substitute for yielding, and pulling straight into traffic without signaling is dangerous and could cause accidents.