You Tell Us: Calm traffic with urban greening
on June 30, 2010
In my last piece for Oakland North, I wrote a problem statement describing the current unsafe situation on the major streets of North Oakland, and broadly proposing some potential solutions. In this piece, I will delve into more specific detail on a specific type of solution, one that pulls double duty: Urban Greening for Traffic Calming.
The basic concept is to take paved portions of the public right-of-way, such as the street or the parking strip, cut out the pavement, build a concrete planter box around it, fill it with good new dirt, and plant it. Conceptually, it’s just that simple, though in practice, there is a lot of nuance that is specific to each location, such as potential utility relocation, remaining travel lane width for fire vehicle access, slope for water drainage, maintenance and watering plans, and species selection.
The benefits come in two categories: The benefits of traffic calming, and the benefits of urban greening. The benefits of traffic calming are realized primarily by reducing the travel lane width and by reducing the crossing distance for pedestrians, as well as giving pedestrians a “lead-off” point from which they can stand in a location “on the curb” — that is, still legally on the sidewalk, but far enough out into traffic that they can see oncoming traffic around the visual obstacles posed by parked cars.
There are additional benefits realized when roadways with multiple lanes in each direction are given a “road diet,” reducing them to one lane in each direction, by denying motorist the opportunity to speed and pass and thus removing the visual and design cues that higher speeds are OK. But, even on roadways that begin with only one lane in each direction, urban greening projects have successfully been used around the world to further slow traffic speeds, reduce accidents, reduce pedestrian injuries/fatalities and reduce noise from vehicles.
The benefits of urban greening include cleaner air, reduced water runoff to storm/sewer systems, more wildlife habitat, more human habitat, opportunities for re-introduction of native plant species to the urban environment, visual aesthetic improvements, reductions in the urban heat island effects and the capture of carbon dioxide, a greenhouse gas that can lead to global climate change.
Urban greening opportunity sites generally fall into three categories: Next to the curb (curb extensions, bulbouts, neckdowns and street meanders); in the middle of the street (planted medians); and in the middle of the intersection (roundabouts and traffic circles). Because most streets are sloped from the crown of the street (the middle) towards the edge, only urban greening projects that start at the edge have the ability to collect storm water from elsewhere in the street through cuts in the curb that allow water flowing down the street to be diverted into the urban greening project and processed by plants before being allowed to seep into the soil and recharge the groundwater table. The implementation of an urban greening plan that was devised using a systems approach would thus logically always pair urban greening projects from the centers of streets and intersections with urban greening projects at the edge of the street, in order to fully capture as many benefits as possible. This approach also leads to better framing of the street, with greening on both sides of the traffic space.
For a corridor such as Market Street from the Berkeley city limit to 40th Street, I would thus recommend the following combination of approaches, combining all of the above design strategies:
• Starting at the intersection of Stanford Avenue, Market would begin its road diet, transitioning to one lane of through traffic in each direction, plus bicycle lanes. This would allow more room for bus stops with landscaped waiting areas, expanded median landscaping and landscaped curb-bulbouts at intersections.
• At the intersection of 57th, Adeline and Market, a large roundabout would replace the current heinous traffic light and terrifying acre of asphalt. Curb extensions would further reduce the asphalt and help to define the circular nature of the travel path through the intersection, serving to reduce speeds and the risk of injury from accidents.
• Related to this, Adeline Street would receive a road diet along its entire length, featuring a landscaped median, bicycle lanes and curb extensions at intersections from the Emeryville border to the Berkeley border. This would allow it to enter the roundabout with only one lane of traffic in each direction. At the southwest side of the intersection, it is likely that northbound traffic on Adeline would get re-routed through the intersection of 56th and Market before continuing on Adeline at 57th.
• The intersection of 56th and Market would likely receive a smaller traffic circle, allowing traffic from Adeline to smoothly merge into traffic on Market Street.
• Adeline southbound from 57th to 56th would receive a street meander, causing traffic to run through a slight S-curve as it exits the traffic circle, before continuing on the regular street design below 56th.
• The existing center turn lane on Market would be replaced with a landscaped median along its entire length, and augmented with sidewalk bulb-outs at intersections to shorten the crossing distance for pedestrians.
• Certain cross-streets would receive neck-downs at intersections, forcing traffic to slow before entering Market Street. A neck-down is when one or two curb extensions are used to narrow a street from two lanes to one lane, either so that traffic in one direction has to wait for oncoming traffic to pass before proceeding, or to create a one-way environment for cars — but two-way for bicycles — such as at the entrance to a bicycle boulevard, to let cars out of a block but not let them in at that intersection.
• The intersection of 55th and Market would receive a traffic circle, as well as extended curb extensions allowing for wide sidewalks in front of the existing neighborhood retail center. This would allow for sidewalk seating in front of cafes, as well as produce displays in front of the grocery store.
• The intersection of 40th and Market would receive curb bulbouts to reduce the crossing distance for all four crosswalks, as well as enhanced landscaping at bus stops.
I use Market Street to illustrate how a systems approach can draw on multiple urban greening strategies to implement traffic calming on a corridor level. This same approach could be used on many of the street corridors in North Oakland to enhance safety and add to the livability of the neighborhood for all of its residents and visitors.
Garlynn Woodsong is employed by Calthorpe Associates, a firm of urban designers, planners & architects located in north Berkeley, to which he commutes 4.5 miles each way every day on his bicycle. He was previously with the Metropolitan Transportation Commission (a regional government for the 9-county Bay Area located in downtown Oakland), and as such is intimately familiar with many land use and transportation planning issues and funding sources. Garlynn has been active in the Longfellow community of North Oakland since buying a house and moving to 42nd street in November of 2008, including involvement with the 40th street median green project and the Longfellow Community Association.
You can read Oakland North’s previous coverage of a median greening project on 40th Street in North Oakland here.
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