The general advice is to self-isolate and not practice social distancing.
Social distancing is the fall back when self-isolation is not possible, such as when exercising or essential shopping.
It stands to reason that the closer you are to other people, the greater the risk, but the safest course of action is to self-isolate and appreciate that anything else is introducing some sort of risk.
The distance is of course only relevant if someone is infected, and then probably only a real issue if they are showing symptoms and sneezing.
We can all play the "is it enough" game, those that want to fully insure themselves will not have any contact with other people, and for times when contact is unavoidable, then it is a sliding scale of risk.
Distance is just one factor, infection rate, surfaces, weather conditions, time in contact, masks, types of mask, area of confinement are some but by no means all, contributing to the overall risk when coming into contact with other people.