Designing Shared Streets for Safety and Usability
by Ken Stewart

(Editor's Note: This proposal was submitted to the U.S. Access Board in June 2007.)

The concept of the "shared street" is increasingly popular nowadays in cities of western Europe, and interest in the idea is growing in the U.S. too. A shared street is usually established in a downtown area where, for a full block, there is no obvious separation between motor vehicles and other users. All users are authorized to move through the block anywhere and yield to other users through a "negotiation" process not unlike what occurs at any signalized intersection when both a pedestrian within a crosswalk and a turning motor vehicle are authorized to proceed. Typically, there is eye contact, from which the motorist concludes whether the pedestrian will speed up or slow slightly to permit the vehicle to cross his path either just in front of, or behind, the pedestrian. That sort of negotiated priority can develop also where there is an unsignalized crosswalk, and a crossing pedestrian waits for a gap in traffic movement unless an approaching vehicle pauses in deference to that pedestrian.

The intention of establishing a shared street is to create a "traffic calming" feature. It has been described as an expression of a desire for civility. Many U.S. cities have converted a particular downtown block to what is commonly known as a "pedestrian mall." It has been converted because there are, or planned to be, many retail, commercial, and other non- residential destinations along both sides of the street. These pedestrian malls are very well received by pedestrian groups, by businesses depending upon heavy drop-in customers such as restaurants, and by the local anti-auto stakeholders.

Resistance is expressed by those who identify the collateral damage caused by the elimination of a previously convenient motor vehicle passage, by those who suffer the negative effects of the diverted traffic, and by any business along the block that wants close and full-time access to trucking or other motor vehicle functions. A shared street offers an apparent compromise between these conflicting interests.

The shared street is intended to eliminate any physical symbols of "territoriality." With no observable edges to the vehicle right-of-way, a motorist is reminded thereby that he has no exclusive route. He must be ready at all times to yield the right-of-way as determined by eye contact negotiations. Walkers, and many other street users on wheels, including skaters, bicyclists, skateboarders, those operating human transporters, baby carriage pushers, people moving in hand-powered wheelchairs, and folks in power scooters, gain great flexibility. They can choose the most direct route between any destinations along that block, and they also vary their paths to avoid clumps of other pedestrians as they wish. Street furniture typically remains where it was if the street was previously a conventional one. A newly developed shared street would likely follow a similar pattern, lining up most items outside of the central corridor.

One user group greatly disadvantaged by the shared street is that class which depends upon obvious visible and tactile "shorelines" to maintain directionality, and is excluded from the eye contact by which movement priority is negotiated. One design technique which can reduce this major disadvantage is the inclusion of a pattern in the street's surface. The pattern must be highly visible and detectable under foot also, but not so prominent that it presents a significant obstacle to easy rolling by all of those moving on wheels but not in motor vehicles. The pattern also must avoid conveying any notion of parts of the area being primarily for trucks and cars, and parts primarily for others.

A "corduroy" pattern would be created by the application of longitudinal seams for the length of the block. Each seam would be three inches in width and one-half inch high, with a rounded crown. Each seam would be in high visual contrast to the street surface. The visual combination could be in any one of several aesthetically pleasing combinations such as chocolate brown seams on a beige surface, or a very light gray seam on a dark asphalt surface. The seams would be separated by a uniform gap, six feet for example. Street furniture would be aligned within the same two seams for the length of the block, typically outside the second seam out from the building line, resulting in a clear channel between the building line and these objects of more than 12 feet.

The presence of longitudinal seams would enable a visually impaired pedestrian to maintain directionality. Those users would remain vulnerable when moving across the street, but they could at least detect a visual and/or tactile basis for aiming across at a right angle, thus minimizing their exposure to more formidable users. By keeping that perpendicular directionality, and avoiding any noticeable sideways facing, they would minimize the expectation of any motorist for negotiations. Of course, the conspicuousness of a long white cane, service animal or stability support would further reduce any expectations for negotiations.

A better design would add periodic lateral seams with the same dimensions and appearance, spaced according to the Golden Ratio so popular with architects. These seams, approximately 10 feet apart if joining six- foot spaced longitudinals, would provide guidance for a visually impaired pedestrian wishing to navigate across the street as directly as possible.

Even more helpful than this "tweed" pattern would be a design creating a "plaid" appearance; if every fourth lateral seam was tripled, it would offer periodic markers for place orientation. The surface feature thus established would also give a visually impaired pedestrian crossing the street more visually and tactually obvious directional guidance. These fabrics of the city might regularize the experience of a cognitively disabled shared street user also.

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