I left it intentionally ambiguous because it is always doable, just more risky in a lot of places and really depends on a persons appetite for it; their personal weights given to a cost/benefit analysis as well as thinking up ideas to reduce that risk (riding as a group, visual cues for drivers, etc).
*Not to mention any and all reasons for using vehicles is essentially placing ones own convenience and comfort over everyone elses safety and health, including their own.