There are three types of roads in Iceland:
Paved roads (P) – speeds up to 90km/h allowed when weather is appropriate
Paved roads are usually the easiest to drive on, but they can sometimes be narrow and winding, especially in rural areas. You should be careful not to drive too fast and always stay on your side of the road.
gravel/dirt roads (G) – speeds up to 80km/h allowed when weather is appropriate
Gravel roads can be slippery, especially when they're wet. You should slow down, especially on bends, to avoid skidding. Also, keep a safe distance from other vehicles to avoid stone chips.
and highland roads (F) – always choose a speed prioritizing safety
Highland roads, also known as "F roads", are mountain roads that are usually narrow, winding, and unpaved. They're only open during the summer and require a 4x4 vehicle.
Always check the road conditions before setting out on F roads. They can often be rough and require careful driving.
River crossings are common on highland roads. Always cross at marked crossing points, and never cross if you're unsure about the depth or current. If the river is too deep or strong, don't risk it.
Damages deriving from river crossings are not covered by insurance.