Dr. Paul Sax, clinical director of the Division of Infectious Diseases at Brigham and Women’s Hospital, writes it might be time to say it's OK for people to go outside without a mask on - but to keep one handy for those inside visits.
Transmissions do not take place between solitary individuals going for a walk, transiently passing each other on the street, a hiking trail, or a jogging track. That biker who whizzes by without a mask poses no danger to us, at least from a resipiratory virus perspective. ...
So he proposes:
Dangerous - crowded indoor spaces with poor ventilation, in particular with unmasked individuals talking, shouting, singing. Wear a well-fitted mask until case numbers are down and more people are vaccinated.
Safe - outdoors, especially while distanced. Masks only needed for lengthy interactions with others at close distance.