Final answer:
When instructed to merge, drivers should merge into the designated lane as soon as possible for safety and to maintain traffic flow.
Step-by-step explanation:
When instructions indicate that all traffic on the same roadway must merge into one lane, the correct action for drivers is B) Merge into the designated lane as soon as possible. This ensures a smooth flow of traffic and prevents accidents. It is important for drivers to stay alert, watch for merging signals, and safely integrate their vehicle into the correct lane. Actions such as staying in your current lane and ignoring merging traffic, speeding up to pass other merging vehicles, or ignoring merging signals and proceeding as usual are unsafe and could lead to traffic violations or accidents.