Existing Conditions
Neighborhood streets are small, and typically have low volumes of through movement in any mode. They are sensitive to their traffic network role, and can quickly degrade if made attractive as a cut-through for motor vehicles. Many such streets are already traffic calmed, often with low-cost measures such as speed humps.
Some neighborhood streets with narrow roadbeds are configured as yield streets, permitting parking on one or both sides, with narrow travel space enforcing low speeds on motor vehicle traffic. Other neighborhood streets are marked with a lane or lanes for through traffic along with on-street parking spaces. Traffic operations are sometimes one-way. Speed is a frequent complaint.
Mature trees and frequent driveways often interrupt the sidewalk, and sometimes limit the ability to site bioretention facilities.
Recommendations
Design local streets for very comfortable walking and all-ages bicycling, while integrating green stormwater infrastructure. These streets serve a multitude of short trips, and present a significant opportunity to integrate stormwater management into the right-of-way.
Due to low traffic volumes and less sediment and debris, neighborhood streets can be ideal right-of-way sites for bioretention facilities and/or permeable pavements. Water from higher traffic cross streets can be conveyed to bioretention facilities on neighborhood streets, which may simplify maintenance access.
The planting strip creates opportunities for large infiltrating surface area; graded bioretention cells may offer a softer urban design adjacent to the sidewalk. Prioritize maintaining mature trees where possible. Consider the use of tree wells and trenches if space is constrained.
Designate the reconstructed street as a bike boulevard, with design strategies to manage motor vehicle speed and volume. A curb extension planter at the downstream end of the block serves as a partial closure to manage motor vehicle volume.
Curb extensions are also proven effective at increasing pedestrian visibility, shortening crossing distance, and calming motor vehicle traffic by enforcing low speed turns and through movements. Bioretention planters sited at curb extensions should be planted with low shrubs and vegetation that maximize visibility.
Mid-block curb extensions are configured to “chicane” the street, managing yield interactions between two-way vehicle traffic and maintaining slow operations. On the narrowest streets, parking and plantings are placed on alternating sides of the street with a clear zone reserved in the center for two-way emergency vehicle access.