Essential Terminology

It's true: the lingo can get a bit daunting, especially when so many of the terms are not strictly defined. Here are some of the more common ones

15-Minute City: A concept popularized by the 15-Minute City Project and based on the notion that “…everyone living in a city should have access to essential urban services within a 15-minute walk or bike.” 

Active Transportation: Ways of getting around, primarily walking and bicycling, that are powered by human energy. Note, though, that bikes, scooters, and other devices powered in whole or in part by electric motors are sometimes included within the definition of "active transportation."

Bicycle Urbanism: a school of thought that places active transportation, rather than cars, at the center of urban planning and design.

Complete Streets refers to a well-established practice, adopted by over 1500 American cities and towns. The Bay Area Metropolitan Transportation Commission (MTC) provides significant federal funding and prioritizes projects that take a Complete Streets approach. By MTC’s definition, Complete Streets are “ and comfortable for everyone, regardless of age, ability, ethnicity, race, sex, income, disability or chosen transportation mode.” Equally important, they maximize “...the use of the existing public right-of-way by prioritizing space-efficient forms of mobility (walking, cycling, shared mobility and public transit) over space intensive modes (single occupancy auto travel).”

Micromobility: Non-automotive ways of getting around that are fully or partially human-powered. The range of such devices is large -- and steadily increasing! -- and includes: bicycles, recumbent bikes, cargo bikes, unicycles, scooters, skateboards, hoverboards, Segways, wheelchairs and more. Micromobility devices most commonly do not exceed speeds of ~15 mph.

Queuing: The instinctive process of drivers yielding to oncoming drivers, as is required on Yield Streets (see below)

Quick Build: A temporary, low-cost test installation of street safety modifications that allows real-world evaluation by people who use the street. If it passes the test, it is easily upgraded using more durable materials. If it fails, it is easily removed.

Road Diet: Most commonly used to refer to a road re-design that results in a reduction in the number of travel lanes. A typical road diet is a conversion from two lanes in each direction to one lane in each direction with a middle turning lane. Road diets typically include the addition of Class II (striped) bike lanes. Road diets are known to result in safer roadways with no reduction in travel times.

Shared Street: a “pedestrian-priority” street designed for slow travel speeds where pedestrians, cyclists, and motorists all share the right of way. 

Sharrow ("SHARE-oh"): Shared lane markings that alert motorists to be aware of bicyclists traveling on the street (see image). Sharrows are probably the most-(ab)used least understood street marking. Motorists should always be aware of bicyclists and other no-car travelers. Sharrows don't provide any protection, and as often as not don't indicate where in the travel lane the bicyclists should ride.

Slow Streets: The term “Slow Streets” gained currency in response to the Covid pandemic in 2020 when traffic volume and traffic speed were intentionally reduced in order to encourage bike and pedestrian activity on urban streets. Slow Streets were often created quickly and inexpensively through the use of signage and temporary barriers. 

Tactical Urbanism: “A city- and/or citizen-led approach to neighborhood building using short-term, low-cost, and scalable interventions to catalyze long-term change.” [Source: City of Burlington, VT: Community-Led Demonstration Project Policy + Guide]. Tactical Urbanism projects are Quick Build projects on a small scale.

Transit-Oriented Development (TOD): The creation of higher-density, mixed-use communities near transit stops where people enjoy easy access to jobs and services.

Vision Zero: A strategy to eliminate all traffic fatalities and severe injuries while increasing safe, healthy, equitable mobility for all. First implemented in Sweden in the 1990s, Vision Zero has proved successful across Europe — and now it’s gaining momentum in major American cities. In 2022, the Petaluma City Council passed a Vision Zero Resolution that sets a goal of zero traffic-related fatalities and serious collisions by 2030. "Unsafe speeds" are identified the single leading cause of all collisions.

Woonerf: A shared-use space designed equally for pedestrians, bicycles, and recreational uses that may allow slow moving automobiles and other vehicles (motorists are considered guests within the woonerf). 

Bicycle Box: An extension to a bike lane providing designated space for bicyclists in front of vehicles while waiting for a green light.

Sharrows: Shared lane markings that alert motorists to be aware of bicyclists traveling on the street. 

Traffic-Calming Devices

Asphalt art: Painting of the roadway surfaces, typically done by the local community, results in reduced vehicle speeds. 

Changes in pavement types: Similar to the effect of Asphalt Art, variations in roadway surfaces put drivers on alert and result in reduced vehicle speeds.

Chicanes: When the roadway ahead is not clearly visible, drivers tend to drive more slowly. Chicanes are intentional wiggles in an otherwise straight roadway. The wiggles are perfect places to plant trees or locate a community gathering place.  

Corner bulb-outs: A narrowing of the roadway at intersections that reduces the crossing distance for pedestrians and reduces the turning radius, thereby reducing vehicle speeds. Mid-block crosswalks can be treated in a similar way.   

Curb extensions narrow the roadway visually and physically, which creates shorter, safer crossings for pedestrians and makes space available for street furniture, benches, plantings, and street trees. A curb extension can be used as a “gateway” treatment to alert motorists that they are entering a slower zone or non-street area.

Edge/Advisory Lane: A narrow two-way vehicle traffic lane that is striped only at the outside edges. Outside the advisory lane are edge lanes for bicyclists where motorists may pass other vehicles after yielding to non-motorized road users.

Mini-roundabout: A small, raised island in the center of a residential intersection for reduction of traffic speeds.

Narrow travel lanes: In the past, wide travel lanes were thought to increase safety. Recent studies show that narrower travel lanes result in reduced vehicle speeds and fewer collisions. On our collector streets and arterials, 10 feet is generally adequate. The recent street improvements on B Street in downtown Petaluma feature 10-foot travel lanes. 10 feet is plenty. 

Yield streets:  Low-volume, low-speed (mostly) residential streets where overall traffic lane width does not allow two vehicles to pass. Vehicle pullouts are provided so that vehicles can easily pull to the side and yield to oncoming vehicles. It is the physical configuration of the roadway, not the posted speed limit, that keeps traffic speeds low (less than 15 mph) and keeps the streets safe. [Source: Urban Street Design Guide, National Association of City Transportation Officials]

Roundabouts or traffic circles move traffic more steadily and smoothly than intersections with timed traffic lights. They continue to function during power outages. Their smaller cousins are mini-roundabouts.

Street trees: Motorists perceive tree-lined streets to be narrower, and therefore drive more slowly. Plus these same trees improve air quality, provide shade, and enhance well-being.