Single track (one lane) roads are very common in rural areas, especially in the Scottish Highlands. 

If you want to let a vehicle pass you, pull into one of the passing places on your left (these are often marked by white ‘passing place’ signs, but not always).

If the closest passing place is on your right and you reach it first, stop on the left side of the road (opposite the passing place) to let the vehicle pass on the right. 

Give way to vehicles coming uphill when possible and if necessary, reverse until you reach a passing place to let the other vehicle pass.

In Scotland it is customary to give a friendly ‘thank you’ wave or flash of your lights if another car has let you pass.