Not really. Many models do have a planning preference for 'walking' but that allows for the travel the wrong way on 1-way streets.
1. Battery power at best is about 2 hours on a full charge
2. As you move when walking, the car icon doesn't move every step you take. It may be 5-10 feet or more for every movement of the icon.
That said, some certainly do use the unit for travel by foot.