Streets - Fundamental Ingredients

The Street Corridor is a community’s primary public realm.  Urban designers call them “street corridors” because, like hallways in a building, they are formed by the buildings on each side.  From building façade to building façade, street corridors are composed with a list of ingredients which themselves can have various individual flavors.

Pedestrian-friendly street corridors are the life-blood of cities, and they all have the same fundamental ingredients.  While the size and character of each can vary, these ingredients should be located in their proper places in order to achieve a walkable environment.  These fundamental ingredients are:

• Vehicular travel lanes / turn lanes

• On-street parking

• Collector Strip / tree strip

• Sidewalk

• Private space (optional)

• Buildings

Motor Vehicle Travel and Turn Lanes

While some denser cities can successfully sustain a few pedestrian-only streets, the vast majority of walkable neighborhoods need to have lanes for cars, buses, and trucks.  Even the most fervent of urban activists should admit, in most of the United States where mass transit is not the primary ingredient, vibrant communities need visitors who have to arrive in cars. Cars are not the enemy, but they can be bullies.

One crucial aspect of urban street design (or re-design) is to NOT let the number of, or width of, travel lanes become excessive.  Traffic engineers have been directed by communities, since before World War II, to make roads that get as many cars and trucks from point “A” to point “Z” as quickly as possible.  The neighborhoods along the roadway (points “B” through “Y”) haven’t mattered as much, resulting in far too many neighborhoods in America becoming places to drive through instead of places to drive to. 

Roadways can easily become too wide.  The pressure put upon policy makers by various interests is to add lanes to roads to increase capacity.  This effort, it is commonly believed, will reduce traffic congestion and unleash development potential “down the road”. The problem is:  when roads are widened, the traffic which ends up driving on them is almost always more than what was forecast.  This is termed “induced demand”.  The futurist, Lewis Mumford, said it best when he assessed the effort to widen roads:  “Widening roads to solve traffic congestion is like loosening your belt to cure obesity.”  Also, narrower lanes (10’ to 11’) do not decrease roadway capacity, but they decrease the length a pedestrian has to walk across a street at a crossing which is a huge benefit – especially for kids and the elderly.

Pedestrians are commonly subjected to a hostile environment where motor vehicles bully through at high speeds.  Wide lanes and roads lead to higher travel speeds, which is less safe for pedestrians and bicyclists.  Even if a city posts speed limits signs all over the place, a street that feels wide will encourage drivers to drive too fast.  A wide road tells drivers: “go ahead, drive faster.”  Many studies have proven that the likelihood of severe injury or death of a pedestrian or bicyclist increases dramatically with every single mile-per-hour a motor vehicle travels.  In fact, a pedestrian is 70% more likely to be killed when hit by a driver travelling 30 mph than at 25mph. 

This problem does not just exist for arterial roadways.  Streets that serve only a few dozen houses can also encourage fast vehicle traffic speeds.  This is particularly troublesome in neighborhoods where kids potentially run free.

Recent technical resources authored by the Institute for Traffic Engineers, Smart Growth America and other groups, is finally helping guide street engineers to design for the pedestrian, bicyclists, and micro-transporters. While the 2018 edition of AASHTO’s A Policy on Geometric Design of Highways and Streets (the traffic engineers’ bible nicknamed the “Green Book”) offers new guidance to traffic engineers for the design of urban roadways, re-engineering our current roadway network will take time and the diligence of people advocating for all modes of transportation.   

On-Street Parking

On-street parking is a vital commodity – especially for small, local businesses.  Aside from generating revenue for municipalities through parking fees, on-street parking has economic value for businesses located along a street.  Several analyses have shown that a single on-street parking space can generate up to $300,000 in annual retail sales for a small business near it.

On-street parking also provides an element of safety and comfort for pedestrians – even on primarily residential streets.  On-street parking, whether in a parallel or angled arrangement, provides what the Institute of Transportation Engineers (ITE) calls: “Street Friction”.  This street friction calms traffic by making drivers feel like they have to slow down.  With short block lengths (i.e. – more intersections) and reasonably narrow road lanes, on-street parking can provide more persuasive traffic calming than any speed limit signage can.

On-street parking can actually provide a vitality for a community simply by hosting cars.  Even newly built “life-style” retail centers have streets with on-street parking spaces.  These “teaser” spaces are highly valued because they are close to the front doors of buildings, easily accessed, and prominent.  Even if on-street parking can’t provide all of the spaces that a business district needs, on-street parking can provide an active-looking environment more so than a large, half-empty asphalt parking lot can. 

Collector Strip / Tree Strip

One of the most important, yet least understood and appreciated, ingredients of a well-designed street corridor is the Collector Strip. Sometimes called the “Furniture” or “Curb” zone, the Collector Strip is the space between the roadway curb and the sidewalk. Many traffic engineers consider the Sidewalk to be the ingredient that extends from the curb all of the way to the back rail of the sidewalk – they don’t acknowledge the Collector Strip as its own element. It is far better to consider these as two separate, distinct elements: the Sidewalk and the Collector Strip. When designers and engineers treat the Collector Strip as its own element, then it can be designed with the appropriate care and significance. It can become a valuable component of a community’s personality and commerce, and will make the pedestrian experience comfortable and even fun.

In areas with detached single-family houses, the collector strip is usually large, grassy and hosts street trees and street lights. 

In more urban areas the Collector Strip hosts standard elements such as street trees and streetlights. But it also holds: bus stops, signage, benches, information kiosks, public art, mailboxes (yes we still have those), bike racks, and even scooters and other micromobility vehicles. It “collects” the street architecture of a district into one linear area.

Unfortunately, too many communities and engineers don’t understand the critical role that a Collector Strip plays in a pedestrian-friendly environment - or they just don’t care. Both the placement and size of a Collector Strip are crucial to making a pedestrian-friendly street corridor.  If it’s reduced in size, especially along a roadway where vehicles drive fast, then it doesn’t help pedestrians at all – even if a community splurges on expensive materials such as brick pavers.  Worse, sometimes street trees, streetlights, and other elements that should be placed in the Collector Strip are positioned outside the sidewalk. 

Design of the collector strip is sometimes a community’s biggest opportunity to customize the civic character it wishes to present to visitors.  Collector strips can be wide or narrow, softscaped or hardscaped, and full of architectural and artistic elements or sparsely filled. The character of a community can largely be presented by what is in the collector strip.

If large enough, a collector strip can host large trees indicating a sense of quality and permanence.

Sometimes collector strips don’t even have to be big to accommodate large trees, which are cherished by a community and integral to their sense of value, stability, and permanence.

If wide enough and well cultivated, Collector Strips can become occupiable spaces where people can dine or gather.

Some communities populate the Collector Strip with special signage, art, and hallmarks of heritage which reveals a community’s personality and grows civic pride. 

SidewalkS

The Sidewalk is actually more of a “public” element than the asphalt roadway that cars and trucks use.  This is for one simple reason: nobody – not one single person anywhere – is required to have a government-issued license to use a sidewalk.  The same can’t be said of the roadway.

The sidewalk is a precious element of a well-connected, vibrant community.  Not only is it the connective tissue for pedestrians, it is also the place where people can talk to one another in a chance meeting.  Unlike while driving, it’s where conversations can happen and human connections can be reinforced.  It is an element of commonality and connection for all people (and their dogs) regardless of their income, age, heritage, beliefs, gender, or physical abilities.  

The design of the sidewalk, in composition with the ingredients around it, will connote the values of a community. Sidewalks can be wider or narrower, and built of any hardscape materials.  They can be serene and peaceful, active and urban, or simply solid and steadfast.

Private Space

Like the Collector Strip, the Private Space – often simply called the “front yard” – is versatile and has the power to show visitors the values and personality of a property within the larger neighborhood. No ingredient of the street corridor can have as wide a range of flavor as the private space.  It can be: large or small, grassy or hardscaped, cultivated or natural, formal or casual, fenced or open, opulent or modest, contemporary or traditional.

By definition, the private space is under the control of a private property owner. Yet it is undeniably a part of the public realm because it is seen and felt by visitors – it is “occupied” by a visitor’s view.  Often regulated by zoning, the size and architecture of the private space can give an overall impression of some civic unity among wonderfully different places and architecture.

The private space can also be a valuable commodity.  It can host sidewalk cafes or the wares of retailers.  The private space is the complex area that links privately owned property – particularly buildings – to the public realm.

Buildings

The framing ingredients of a good, urban pedestrian-friendly Street Corridor are the buildings along both sides of it.  The size and placement of the buildings lining a street help give a Street Corridor its scale and intensity.  Taller buildings spaced closely will give the feel of a more intense environment, while shorter buildings spread farther apart will give the feel of a less intense environment. For a more detailed look at Buildings Forming Street Corridors click here.

While most street corridors in existing cities already have their proportions pretty well established, cities evolve and transform.  New buildings replace old ones, and new buildings fill vacant lots, giving new opportunities to re-frame a community’s character over time.  A well-prepared community will set its zoning according to a desired future so new buildings will shape the Street Corridor a community wants.