Defining Safety

Jane Jacobs defines a safe city street as having three qualities:

     1) There must be a clear demarcation of public and private space.

     2) There must be eyes on the street belonging to the "natural proprietors" of the street; they cannot turn their backs or blank sides on it and leave it blind.

     3) There must be users on the sidewalk continuously.

But is this criteria enough? At what point does the nature of a bad stranger overcome the safety of the street.

The Piazza de Ferrari and Via XX Settembre in Genoa, Italy together present an excellent case to be considered "safe". Piazza de Ferrari is a very popular public square in Genoa, surrounded by bank headquarters and office buildings, as well as the Palace of the Doges and the Theatre Carlo Felice, a popular theater. On the ground levels of these buildings are small trattoria that were typically jammed with people trying to get their afternoon cappuccino. As you follow Via XX Settembre from the piazza, you walk inside an arcade of columns, protected from the fast paced nature of the Italian drivers. As you're walking you pass by many stores selling various types of foods, and fashions. In these two places, there is a clear division of what is public and what is private, the collonade extending down from the floors above clearly marks where the sidewalk ends and the street begins. The numerous stores lining the street constantly provide a natural security, and because there is a wide variety of shops, the street is constantly filled with people. There is a sense of security in numbers.

Via XX Settembre, Genoa, Italy

Via XX Settembre seems like a very safe street to me, but what happens when those numbers become too great, like Times Square in New York City? What happens when a street becomes too "safe"? As I see it, the continuous use of the sidewalk quickly becomes a breeding ground for crime. A graph showing the safety of the street in relation to the amount of people on the street would  be a bell-curve. It's true that an empty street is less safe than one with people on it, but as the amount of people grow, that sense of safety begins to decline back down to the levels of that of an empty street. Streets then become crowded, an easy opportunity for pickpockets to do their work, or, even worse, a terrorist.

Times Square, New York City, New York

I guess what my question to all of this is, at what point does a safe street become un-safe and is there anything that we as designers can do to prevent this?

We could all just be like this guy