How fast should one walk? It depends on circumstances; it depends on the aim of the walk.
Recently someone in the group had been asked at her GP’s practice What is your average walking pace? She thought 2 mph. This included stops for refreshment. However, she can walk faster than this and, I think, should not have included stops.
The faster one is able to walk the longer one might live. An Australian study in 2011 highlighted this. A speed above 3 mph is a good aim.