The Scottish Government has clarified its advice on walking and outdoor exercise for those who live in areas under Tier 3 or 4 restrictions.

The new guidance states that if you live in a tier 3 or 4 area, you are permitted to travel upto 5 miles out of your local authority area in order to go for a walk or other form of outdoor exercise. Walks (and bike rides) outside your local authority area are also permitted if the walk (or bike ride) starts and ends within your local authority.
The full new guidance on travel is available here.
Those living in tier 0, 1 or 2 areas should avoid any non-essential travel into areas in a higher tier.