In slow-moving traffic, the zipper merge helps keep traffic moving. If you're approaching a merge point, stay alert, be courteous, and obey posted signs to help you merge safely. | Pennsylvania Department of Transportation (PennDOT)

Lane merge gone wrong | Trucking life with shawn

Always use all of a merge lane to merge – this gives you time to get up to speed and find a safe gap to merge like a zip. Merge lanes taper to naturally guide you into the flow of traffic. When you're merging, always merge at the end of the merge lane. Using all the merge lane: • gives you time to smoothly match the speed of people travelling on the road • gives you a predictable point to enter the road, so everyone around you knows what you're doing and can make room for you to merge like a zip