Terrorism and T-shirt vendors.

"At 6:28 p.m.... a video surveillance camera recorded what was believed to be the dark green Nissan S.U.V. driving west on 45th Street. Moments later, a T-shirt vendor on the sidewalk saw smoke coming out of vents near the back seat of the S.U.V., which was now parked awkwardly at the curb with its engine running and its hazard lights on. The vendor called to a mounted police officer, the mayor said, who smelled gunpowder when he approached the S.U.V. and called for assistance. The police began evacuating Times Square, starting with businesses along Seventh Avenue, including a Foot Locker store and a McDonald’s."

Take a moment to appreciate street vendors. Think of the value of their alert eyes at street level in the busiest places. Let's reflect again on what Jane Jacobs wrote in her brilliant book "The Death and Life of Great American Cities":

A well-used city street is apt to be a safe street. A deserted city street is apt to be unsafe. But how does this work, really? And what makes a city street well used or shunned? ... A city street equipped to handle strangers, and to make a safety asset, in itself, out of the presence of strangers, as the streets of successful city neighborhoods always do, must have three main qualities:

First, there must be a clear demarcation between what is public space and what is private space. Public space and private spaces cannot ooze into each other as they do typically in suburban settings or in projects.

Second, there must be eyes upon the street, eyes belonging to those we might call the natural proprietors of the street. The buildings on a street equipped to handle strangers and to insure the safety of both residents and strangers, must be oriented to the street. They cannot turn their back or blank sides on it and leave it blind.

And third, the sidewalk must have users on it fairly continuously, both to add to the number of effective eyes on the street and to induce the people in buildings along the street to watch the sidewalks in sufficient numbers. Nobody enjoys sitting on a stoop or looking out a window at an empty street. ... Large numbers of people entertain themselves, off and on, by watching street activity.

The basic requisite for such surveillance is a substantial quantity of stores and other public places sprinkled along the sidewalks of a district; enterprises and public places that are used by evening and night must be among them especially. Stores, bars and restaurants, as the chief examples, work in several different and complex ways to abet sidewalk safety.

First, they give people -- both residents and strangers -- concrete reasons for using the sidewalks on which the enterprises face.

Second, they draw people along the sidewalks past places which have no attractions to public use in themselves... Moreover, there should be many different kinds of enterprises, to give people reasons for crisscrossing paths.

Third, storekeepers and other small businessmen are typically strong proponents of peace and order themselves; ... they are great street watchers and sidewalk guardians if present in sufficient numbers.

Fourth, the activity generated by people on errands, or people aiming for food or drink, is itself an attraction to still other people.

Thanks to the guardians of the street.