"To understand how asphalt edges are formed in an asphalt driveway; lets first compare them to the edges of a concrete driveway. A concrete driveway has nice straight formed edges. When a concrete driveway is being installed forms are used to contain the concrete so once the concrete is dry, it creates that straight edge.
With asphalt edges, it’s much different. Since the asphalt is installed using a paving machine, there are no forms used, therefore they tend to have a rough edge and sometimes may even have a slight angled edge to them. As the driveway is being rolled and compacted, these edges can then be compacted with the rakes to make them more durable. It's not a straight edge or a perfect edge, but compacting them will make them look better and increase the durability.
During the grading process,
a row of material should be left along the edge of both sides of the driveway so once the asphalt is finished the crew can pull the material over those asphalt edges. This gives the driveway the appearance it’s sitting down into the soil rather than
simply just being laid on top.
Structurally it’s even more important. If the edges of an asphalt driveway are not dressed, they become susceptible to
cracking and
breaking off. The soil acts as a transition from the edge of the asphalt, helping to keep the asphalt from cracking and eventually breaking off. If a vehicle drives off of the edge, the asphalt can crack and break off or even leave a
tire imprint. This is especially true and can become a much bigger problem if your driveway is elevated. Eventually the
cracked edges can break completely away, which unfortunately, is
not repairable. Trying to patch these areas is only a short term solution. Newer asphalt will not bind properly to the older asphalt and with nothing to hold that patch into place, these cracks or broken pieces and will continue to crack and break away each time they are repaired."
https://allaboutdriveways.com/asphalt-driveways/faqs/asphalt-installation/asphalt-edges/
