Pedestrian Safety Guide and Countermeasure Selection System

 

Case Study No. 108

Terry Avenue North Shared Street

Seattle, Washington

Prepared by Lesley Bain, AIA, Weinstein A|U, and Barbara Gray, City of Seattle, Seattle, Washington.

Problem

When the Terry Avenue North Street Design Guidelines were being written, Seattle's South Lake Union neighborhood was transforming from a low density, former industrial zone to one of the fastest-growing urban districts in the nation. The new neighborhood would need open space and strong pedestrian connections to support the many people working and living in new concentrations of offices.

Background

Faced with the upcoming surge of development, Seattle's Department of Planning and Development and Department of Transportation recognized that Terry Avenue North offered an opportunity to create a street that would add to the character of the evolving neighborhood, with cars and pedestrians sharing the street.

Terry Avenue North had the qualities needed for a model pedestrian oriented street. Only six blocks long, the segment of street carried few vehicles. Its north end led to a new waterfront park on Lake Union. A major arterial and a shift in the grid discouraged both traffic and pedestrians at the south end. The low volume and speed of vehicles was a prerequisite to allowing pedestrians to share the space in the street. In fact, people were comfortable walking in the street before the neighborhood developed. And the planned development would bring lots of people and activity to the neighborhood.

Solution

The City installed a 2-in curb rather than the standard 6-in curb to encourage shared use of the street.

The guidelines took the attitude that the design of the street should respond to future adjacent land uses, supporting pedestrian desire lines across the street rather than requiring crossing at intersections. The idea of clustering, as opposed to the standard linear design approach, is central to the guidelines. Instead of a line of street trees, larger landscaped areas meant that larger tree species could be planted. Small groupings of angled parking could be tucked between landscaped areas. Open spaces could be placed adjacent to building entries, pedestrian paths or a trolley stop. With a shared-use street, pedestrians were able to walk between open spaces anywhere along the block.

The right-of-way is wider than most city streets, varying between 71 and 76 ft. The guidelines created three basic zones within the right-of-way. A portion of the west side of the street had recently been improved with a standard sidewalk, street trees and parallel parking, setting the approach to the west zone. The guidelines created a 23-ft central zone for vehicles and the new trolley line. Instead of following a standard linear approach on the west side, a 31-ft wide zone offered space for pedestrians, with clusters of landscaping and angled parking. No more than 5 parking spaces were allowed in a cluster.

The zone approach solved multiple challenges. First, it set dimensions for the street so that the street could be built out over time. Because the street improvements would be put in place only as development occurred, the guidelines needed to account for incremental development. Second, the intent of the guidelines was to maximize flexibility for the designers of each development along the street. Designers could choose--within the zone--where parking, landscaping and open space was best located for each building.

The idea of a curbless street was considered, with the intent of making the street as pedestrian-oriented as possible. Removing the curb would have created a condition where people with limited vision would have difficulty distinguishing between pedestrian-only areas, and zones where vehicles were allowed. The Americans with Disabilities Act called for a 3-ft wide tactile warning strip with high contrast from adjacent material. Because the guidelines were trying to de-emphasize the linear quality of the street, another option was necessary. The City agreed that a 2-in high curb was acceptable, rather than a more typical 6-in curb. The higher curbs were used as wheel stops for angled parking.

Results

Terry Avenue North has become a vibrant street with a lot of pedestrian activity.

Since the Terry Avenue North Street Design Guidelines were adopted, much of the street has been built out, with high-tech offices and the headquarters of Amazon. The new South Lake Union trolley has begun service to Downtown. Terry Avenue North is a vibrant street, with adjacent open spaces and connecting pedestrian routes. It is filled with people, especially during sunny days. The blurring of plaza space and right-of-way has been very successful. There is less continuity in material between vehicle and pedestrian zones than envisioned, but this can happen over time. Part of the vehicle zone has been paved with brick, indicating that pedestrians are welcome to cross mid-block. The build-out of Terry Avenue North is an excellent step forward in showing the way for pedestrian-oriented street design.

Although no formal pedestrian safety evaluation has been conducted, one of the expected outcomes of the conversion of this six-block street section was expected to be an improvement in pedestrian and motorist safety. This is due to the amenities that were installed for the purpose of slowing vehicle speeds dramatically, as is typical with shared streets.

Contact

Lesley Bain, AIA
Weinstein A|U, Lesleyb@weinsteinau.com, (206) 443-8606
Barbara Gray,
City of Seattle