They make it harder to get from place to place.
Barrier
The mountains were a barrier.
Mountains
A transportation barrier is a natural barrier like mountains, rivers, oceans, etc that blocks or slows the way of transportation.
no
Mountains.
rocky mountains
Rocky mountains
Appalachian mountains
The Appalachian Mountains provided a natural barrier to the western expansion of the English Colonies in America, or so some thought.
They are a barrier to travel and settle ment because of the snow and there peaks
The Rocky Mountains and the Appalachian Mountains have influenced migration patterns in America. The Rocky Mountains acted as a natural barrier to westward expansion, while the Appalachian Mountains presented a barrier to early settlers moving westward from the eastern colonies.