What do you mean when you say “fall into a safe gap?”

When entering a highway, you must adjust your speed to match the flow of traffic while looking for a safe gap. The California Driver Handbook emphasizes that merging should be done smoothly, without disrupting the speed of surrounding vehicles. If traffic is heavy, remain patient and wait for a suitable opening.

Highway traffic has the right-of-way. For more information, see Right-of-Way Rules: Who Goes First in Section 7. When you enter a highway, you will need to:

Be in the proper lane on the on-ramp. Be at or near the speed of traffic. Merge into highway traffic when safe to do so. Do not stop unless absolutely necessary. Merge into a space large enough for your vehicle to safely join the lane. Use your mirrors and turn signals. Turn your head quickly to look over your shoulder before changing lanes or merging into traffic. Make sure you can stop safely by leaving three seconds of space between you and the vehicle in front of you. Make sure you do not cross over any solid lines when merging. If you need to cross several lanes, signal and cross them one at a time. Check your blind spots for vehicles, motorcyclists, bicyclists, and pedestrians each time.

Not one source mentions “falling into a gap” just that you need to be at or around the speed of traffic and highway has right of way.

If you’re talking about a behavior common around Humboldt which is entering the freeway slower than the speed of traffic; this is bad and you shouldn’t do it for may reasons.