Boulevard

Large boulevards with multiple wide roadbeds are often overbuilt for vehicle traffic.

Many cities are restoring these boulevards into vibrant, iconic urban streets, with increasing opportunities to increase safety and comfort for people using the street, capture stormwater runoff, improve shade coverage, and reduce reflective surfaces. These ecosystem services are key to making broad streets into good human habitats.

Existing Conditions

Urban boulevards have historically been designed to maximize automobile throughput, often resulting in poor conditions for people walking, biking, and riding transit. Like other wide arterials, they are prone to frequent speeding and unsafe vehicle operations, but are vital routes for all modes.

Land use and destinations are often mixed and dynamic, with many different types of users and visitors. Both through movement and destination access are in high demand.

Boulevards include broad swaths of impermeable surface that exacerbate stormwater runoff and outfall events. A wide right-of-way with multiple roadbeds creates a complex context for managing a significant volume of stormwater runoff. During heavy rainfall, the service roads—where most walking and bicycling activity takes place—are at particular risk for fast-moving runoff streams and pools.

Recommendations

Boulevards provide some of the greatest opportunities for green stormwater infrastructure in cities, due to their large impermeable footprints and extraneous motor vehicle areas. Service road medians and curbsides provide significant space for water retention, storage, and treatment.

1Mature trees—which perform significant stormwater management—and historic or unique urban design can be found on many boulevards, and should be used to anchor public space and placemaking opportunities. Integrate water management into the aesthetic of the street to create high-quality, comfortable places for people, while designing to protect and promote the root structures of mature trees.

Choose a low target speed and design the entire street around that speed in order to reduce space consumption by motor vehicles, especially at lateral shifts. Compact slip lanes that enforce very low-speed access to the service roads unlock additional pedestrian and green infrastructure space.

2This left turn lane has been shortened and signalized, and the median has been extended as a refuge. Boulevards require careful design at intersections with cross traffic. Enable pedestrians to make safe, easy crossings at desire lines at each intersection, and at least every 300 – 400 feet on long blocks. Manage or restrict turns from the center roadbed to eliminate unsafe turning conflicts.

3Transit stops and stations, especially on the side median, are ideal siting opportunities for bioretention facilities, and may be continued as linear pedestrian spaces to improve pedestrian access and comfort.

Though center median facilities provide large linear footprints, they may be more expensive places to implement bioretention facilities, as they are often difficult to access for maintenance and may require reversal of the roadway cross slope to redirect stormwater runoff to the median. Assess costs of siting bioretention facilities in the median in context with potential benefits, and consider whether street trees are better suited to that space, which still improve shade canopy and perform some infiltration.

4Where space is available, bioretention swales with graded side slopes (see Bioretention Swale) may allow gentler transitions from the pedestrian path to the bioretention facility and allow wider diversity in plant selection. The bioretention facilities can also provide a buffer between the pedestrian path and motor vehicle traffic, especially along the side median.

Local deliveries access abutting businesses on the service roads. Freight access management is an important tool to mitigate safety conflicts on multi-way boulevards. The center road beds of boulevards are often key truck routes, and are sometimes designated as such; 11-foot right lanes on the center roadway are often appropriate , though other lanes should be 10′. The service roads should be distinct in design to discourage trucks from using them as through routes.

5All ages and abilities bike facilities should be prioritized along boulevards and other continuous major streets due to the available width and demand for local and regional bicycle traffic. Permeable pavement may be used for the bike route as long as run-on from adjacent impervious areas is minimized. Utilize pervious concrete or porous asphalt to ensure the surface is compatible and comfortable for bicyclists.

Boulevards with high vehicular use and truck traffic will generate large sediment and debris loads depositing into bioretention facilities, requiring larger-than-typical pre-settling zones at inflow points.