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Asphalt and tarmac are not the same thing. Traditional tarmac, short for tarmacadam, uses tar as a binder to hold crushed stone together. Asphalt uses bitumen—a byproduct of crude oil—to bind aggregate. Though tarmac was once a go-to for roads, asphalt has become the modern standard. And these days, most surfaces referred to as “tarmac” are actually asphalt. So, while the names may overlap, the key distinction lies in the binder—tar for tarmac and bitumen for asphalt.

Three inches is a great thickness for a residential asphalt driveway that sees minimal to moderate traffic from cars, SUVs, and pickup trucks. However, a thicker driveway can better withstand the weight of a heavier vehicle, such as a trailer or a recreational vehicle. If you drive a heavy vehicle on a thin driveway, you risk cracking and damaging it.

You can pour concrete over asphalt if it’s in good condition, thick, stable, and well-compacted. Concrete is more durable than asphalt and can extend the lifetime of your driveway without having to pay frequent asphalt driveway repair costs or replace it completely. 

But this is best reserved as a temporary solution based on budget restraints, as asphalt requires more frequent repairs and assessments than concrete. Once that concrete top is poured, it’ll be harder to accurately understand what’s happening beneath that layer, which could lead to more issues.

An ideal driveway gradient is between 2% and 5%. Anything lower than 1% or higher than 15% can cause problems for your car or property. A driveway with less than a 1% slope increases your likelihood of flooding and water damage, while a driveway with a 15% grade or higher can be too steep for safe traveling.