The biggest mistake to avoid in Iceland is driving roads your car isn't equipped for

• On a trip to Iceland, I came across a group of tourists whose car was stuck at a black-sand beach.
• There are three types of roads in Iceland: paved roads, gravel roads, and F-1 or mountain roads.

While walking back from Víkurfjara beach in Vík, Iceland, during a trip there this summer, I encountered an unfortunate group of tourists whose car was slowly sinking into the black sand.

A one-lane gravel road led to the beach, but it appeared that this group tried to park too close to the shore and ended up in the sand by mistake.

I tried to help them push the vehicle out of the hole, but the more they revved the engine, the further the wheels dug into the soft ground.

It reminded me of the warning I'd received while picking up my rental car upon landing in Iceland: Don't drive on roads that your car isn't equipped for.

Iceland's unpaved and mountain roads require capable vehicles

The car-rental employee told me that there are three types of roads in Iceland: paved roads, gravel roads, and F-1 or mountain roads, which are only open for parts of the summer and require four-wheel drive to navigate safely.

She advised me to watch out for road signs indicating rough terrain and to save the rental company's phone number for roadside assistance in my contacts, just in case.

According to Frommer's, only about one third of all roads in Iceland are paved. During my trip, I found that all of the main streets and highways were paved, but roads leading to many tourist sites such as waterfalls, rural hotels, and beaches were made of gravel.

Because gravel roads can kick up rocks and damage the body or windshield of a car, my rental company also recommended gravel protection insurance as part of its platinum insurance package, which cost €31 (about $34) per day.

Luckily, the SUV I rented didn't have any issues driving the roads. But seeing a group of tourists get their car stuck in the sand served as an important reminder to drive carefully and follow local instructions while navigating unfamiliar terrain.