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Global Designing Cities Initiative-Global Street Design Guide
By Island Press ISLAND PRESS
Copyright © 2016 National Association of City Transportation Officials Consultant Team
All rights reserved.
ISBN: 978-1-61091-701-8
CHAPTER 1
Defining Streets
With 75% of the world's population expected to be living in cities by the year 2050, urban streets will need to balance demands for increasing personal mobility and access to the city economy. Where the low-density, auto-centric development patterns of the 20th century have failed, dense cities with robust multimodal transportation networks are best suited to provide sustainable growth, equal economic opportunity, and a high quality of life. Walkable, cyclable, and transit-oriented neighborhoods are what today's urban dwellers need and demand.
The capacity of urban streets must be increased in ways that support the urban context and ensure a high-quality public realm. This can be achieved by prioritizing sustainable modes of transportation through dedicated space, allowing high-efficiency modes like transit to leave more room for other street activities that support urban life.
As cities grow upward, inward, and outward to serve changing populations, it is critical to consider the many players and processes that shape streets. Our streets are integrally tied to other urban systems, and designing them well offers multiple benefits to cities and their residents.
1.1 | What is a Street
A street is the basic unit of urban space through which people experience a city. It is often misconceived as the two-dimensional surface that vehicles drive on when moving from one place to another. Streets are, in fact, multidimensional spaces consisting of many surfaces and structures. They stretch from one property line to another, including the building edges, land uses, and setbacks that define each side. They offer space for movement and access and facilitate a variety of uses and activities. Streets are dynamic spaces that adapt over time to support environmental sustainability, public health, economic activity, and cultural significance.
Streets are like outdoor rooms shaped by multiple planes: the ground plane at the bottom, the buildings and the roadbed edges as the side planes, and the canopy plane like the ceiling of the room. Each plane is constructed of many individual elements that are often regulated or created by a range of different policies, codes, guidelines, and building practices.
Understanding the various portions of a street as either continuous or interchangeable offers a flexible approach to street design. While sidewalk clear paths, bike lanes, and travel lanes must be continuous and connected in order to function effectively, interchangeable elements such as parking spaces, trees, parklets, and transit stops allow a street to be adapted to serve its context. The terms below broaden the definition of street.
Right–of–Way
The entire distance from building edge to building edge.
Sidewalk
Dedicated space with clear walking paths and universal access used for a variety of activities and functions. See 6.3.4: Sidewalks.
Roadbed
The space between the two sidewalks that can be designed to carry various modes of transportation and their ancillary facilities.
Transit Facilities
Dedicated space within the roadbed for different types of transit to travel on. See 6.5.4: Transit Facilities.
Service Infrastructure
The utilities and services provided within the space of the right-of-way.
Street Activity
Social interactions, neighborhood activities, and citywide events that take place within the street.
Street Furniture
The objects, elements, and structures placed within the street.
Building Edges
The collection of building facades, windows, setbacks, signs, and awnings that define each side of the street.
Travel Lanes
The dedicated space within the roadbed for motorized vehicles to move on. See 6.6.4: Travel Lanes.
Ancillary Lanes
Dedicated spaces for stationery cars, cycles, transit vehicles, loading and unloading zones.
Cycle Facilities
Dedicated space for cyclists to travel. This can be within or separate from the roadbed. See 6.4.4: Cycle Facilities.
Planting
Trees, planting beds, and green infrastructure within the sidewalk, between parking spaces, or in medians. See 7.2: Green Infrastructure.
1.2 | Shifting the Measure of Success
After decades of designing streets to move large numbers of vehicles as efficiently as possible, cities are finally rediscovering the benefits of designing safe and livable streets that balance the needs of all users. It is time to change practices and redefine what constitutes successful streets. Streets should not be evaluated in isolation or as transportation projects alone. Instead, each design presents an opportunity to ask what overall benefits can be gained.
Public Health and Safety
Every year, millions of people die unnecessarily from preventable causes, such as traffic violence or chronic diseases related to poor air quality and lack of physical activity. Street design must promote safe environments for all users and offer healthy choices that facilitate active transportation, such as walking, cycling, and using public transit. Streets should improve access to healthy food options, mitigate noise levels, and provide landscaping and trees that improve air and water quality.
Quality of Life
Cities around the world are competing for the title of 'most livable city' — a recent measure of success — acknowledging the value of quality-of-life measures in attracting and retaining residents and businesses. As people experience a city through its public spaces, the livability of a city is highly dependent on its streets. Shaping how safe, comfortable, efficient, and vibrant a city's streets are will affect how livable it is and how connected its citizens feel. Streets can encourage social interaction, and designs that offer natural surveillance and help build stronger, safer communities.
Environmental Sustainability
In the face of unprecedented climate challenges, street projects provide an opportunity for local actions to improve the environmental sustainability and resilience of a city. Promoting sustainable transportation modes through well-designed streets can lower carbon emissions and improve overall air quality. Incorporating trees and landscaping can improve water management, foster biodiversity, and increase access to the natural environment.
Economic Sustainability
Great streets attract people and business. Street projects that increase safety, improve public realm quality, and welcome multimodal use have positive economic effects such as higher retail sales and increased property values. Investment in streets has long-term economic benefits.
Social Equity
In an era of increasing inequality, cities must ensure that their most valuable public spaces offer safe and equitable use to all, regardless of ability, age, or income, empowering the most vulnerable users with safe and reliable mobility choices.
A city serves its citizens better through street design that increases access to jobs and schools, benefits individual health, improves sanitation, and encourages strong communities.
1.3 | The Economy of Streets
A safe, vibrant, efficient street network is essential to the economic health of a city or region. Street design also plays a major role in facilitating access to formal and informal commerce, jobs, or the wholesale movement of goods. The up-front costs of constructing a street should be considered with regard to the benefits its design will confer throughout its lifespan. Cost impacts of street design should be considered for individuals through value of travel time, public transportation access, fuel costs, and individual health, while the larger externalized cost to society can be examined through expenses such as those related to traffic crashes, hospital costs, negative environmental impacts, and congestion.
Health and Human Lives
The cost of lives lost and serious injuries caused by road crashes have a significant impact on the economy. Better-designed streets relieve mental and physical stress, lowering medical expenses and the need for social services.
Work and Productivity
Significant numbers of human working hours are lost as a result of time spent in congestion or injuries incurred in road crashes. These lost hours result in reduced productivity and, therefore, economic losses.
Business and Real Estate
Pedestrians, cyclists, and transit riders generally spend more money at local retail businesses than people who drive cars, underscoring the importance of offering attractive, safe spaces for transit riders, pedestrians, and cyclists. Great streets have also been shown to add value to neighborhoods.
Construction and Maintenance
Narrow streets cost less to build and maintain. Using good-quality, durable materials can significantly reduce maintenance costs. Green alleys or streets and tree planting are estimated to be 3-6 times more effective in managing stormwater and reduce hard infrastructure cost.
1.4 | Streets for Environmental Sustainability
Designing streets that respond to their environment can help cities meet the challenges of a warming planet. Various international organizations and agendas, such as the UN Sustainable Development Goals, have increased the focus on environmental sustainability, greenhouse gas emissions, and global warming. It is the time to promote the environmental benefits of great streets. Investment in sustainable streets can be attracted by highlighting improved environmental impacts and increased contribution toward achieving a city's environmental goals.
Microclimate
Street trees and landscaping can assist in improving the local climate and reducing urban heat islands, thus minimizing the demand on energy-intensive air-conditioning in vehicles and adjacent buildings.
Noise
Urban trees can reduce noise pollution.
Air Quality
Streets prioritizing pedestrians, cyclists, and transit help to reduce the number of personal motor vehicles circulating, reducing emissions and air pollution.
Water Management
Incorporating green infrastructure strategies and local plant species within streets helps manage stormwater and reduces irrigation needs. See 7: Utilities and Infrastructure.
Health and Safety
Urban trees and vegetation help decrease stress and aggressive behavior in cities and have been linked to crime reduction.
Energy Efficiency
Street projects can contribute to improving a city's energy and resource efficiency by using recycled and low-impact materials and technologies as well as renewable energies.
1.5 | Safe Streets Save Lives
More than 1.2 million people die on roads around the world every year. That is equivalent to roughly one person dying every 30 seconds, or over 3,400 people dying every single day of the year. Many of these deaths occur on urban roads and are preventable crashes caused by behavior induced by street design.
Creating safe streets is a critical responsibility shared by designers, engineers, regulators, and civic leaders. Even in the cities with the best safety records, the threat of traffic violence makes movement around the city a potentially dangerous daily activity. Highway-like street designs that prioritize automobiles over vulnerable users and encourage high speeds fail to provide safe environments.
A New Paradigm for Safety
The new paradigm for safety is built on human limits. The human body is fragile and can only survive certain forces. This means:
• Reducing exposure to the risk of conflict
• Reduce crash numbers and the severity of impact by
• Reducing speed
• Shaping streets that are safe for vulnerable users
When vehicles move at or below 40 km/h, potential conflicts take place at lower speeds, dramatically increasing the chances of survival in the case of a crash.
Studies from around the globe have shown that most traffic deaths, especially the easily preventable pedestrian deaths, occur on a small percentage of arterial streets. These streets are rendered dangerous by design. They contain the following characteristics:
• Wide streets that invite speeding and lack safe crossings.
• Streets that act as front yards but allow aggressive behavior by those passing through.
• Highway-like surface streets where motorcyclists and public transport passengers are at risk from large speed differentials, and where sidewalks are missing or substandard.
The combination of high traffic speeds and volumes, long crossings, and large distances between marked crossings make them fatal corridors for vulnerable users.
Common Causes of Traffic Fatalities
Many traffic injuries are directly related to design. Conditions become more dangerous with the addition of speed. Common causes for traffic fatalities include the following:
• Lack of Sidewalks: When the sidewalk is blocked, narrow, or nonexistent, pedestrians are forced into the roadbed. This presents a particular threat when the street is designed for fast-moving vehicles, and not designed to accommodate all users safely.
• Lack of Accessible Crossings: Pedestrians are at risk of being struck when accessible crossings are not provided or are inaccessible. Mid-block pedestrian crashes are very common on large streets, where vehicle volumes and speeds are prioritized over sufficient opportunities for safe crossing.
• Lack of Protection: Wide, multi-lane streets without refuge spaces expose pedestrians to moving vehicles for longer distances as they cross the street. This is particularly unsafe for the elderly or those who move at a slower pace.
• Lack of Predictability: When signals and countdown clocks are not provided, or when signal cycle lengths result in a long wait time, pedestrians are unable to safely judge the time they have and are more likely to cross unsafely.
• Lack of Cycle Facilities: Cyclists are at risk of rear-end and overtaking crashes when mixing with motor vehicles at moderately high speeds, especially on multi-lane streets.
• Poor Intersection Design: Large intersections are often designed for dangerous, high-speed turning. Lack of visibility results in poor navigation and assessment of different users' movements.
• Unsafe Boarding Areas: Transit riders are at risk when boarding and alighting vehicles in traffic, especially if no safe facilities are provided. Higher-speed streets and poor intersection design near boarding areas increase chances for severe crashes and put vulnerable users at risk.
• Surface Hazards: Obstacles and surface degradation, including potholes, can present hazards to pedestrians and cyclists.
Safe Design Supports Education and Enforcement
Regulations and education are critical to creating a culture of safety. However, a street cannot be made safe if it has been designed to prevent people from making safe decisions. Most road safety agendas focus on reducing probability of human error through education and enforcement, without emphasizing the design of safe streets. Design can ensure that a crash or conflict caused by human error will be limited in its severity. The design of a street is often far outside the scope of a safety project, but it can have direct and indirect impact on the safety of street users.
Vision Zero and Sustainable Safety Programs
The Vision Zero (initiated in Sweden) and Sustainable Safety (initiated in the Netherlands) programs are proactive safety programs being adopted by an increasing number of cities around the world. The premise of such programs is that loss of life is unacceptable, and their goal is preventing all serious road crashes. These initiatives place the burden of safety on the system design, not the road user. Innovative street designs that reduce speed, strict enforcement against traffic violations, legislative ordinances that lower speed limits, and public awareness campaigns have proven to be impactful strategies adopted by these programs.
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Excerpted from Global Designing Cities Initiative-Global Street Design Guide by Island Press. Copyright © 2016 National Association of City Transportation Officials Consultant Team. Excerpted by permission of ISLAND PRESS.
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