It's very different in very area, but the reason here in Canada they don't seal the highway, roadways is: 1)- They wouldn't let cars on for at least 48 hours for the drying time, this would be a headache with a lot of traffic going on. 2)- It would be very expensive to seal the highways/ roadways (but very little compared to paving. 3)- Roadways and highways are made with a much thicker base and thicker asphalt, they are compacted way more than residential driveways *In short the asphalt for highways and roadways are made to LAST, good highways will be able to survive 30+ years in Canada with the harsh winter and salt we have. They build them very tough to survive traffic and heavy duty use. Residential driveways are not the same, they are build way more cheap. Most driveways here that are 800 sq.foot will cost about 3gs to pave, and about 200$ to seal every 2-3 years. residential driveways here have: 12inches of base, with 1-2 inches of asphalt compacted. True fact: The 417 (one of the big highways in Ontario) has 24inches of base, with 6 layers of 2inches of heavy duty compacted asphalt. That's why they don't bother sealing it because the asphalt is made to last, although they still do fix the cracks as some point.