Image showcases a typical New York City intersection with wide lanes of traffic.
Photo Credit: Unsplash

About.

Sidewalk Labs’ mission is to radically improve quality of life in cities. The ability to confidently and comfortably ride a bike or meander down the street is critical to that mission. So is the ability to get where you need to go as efficiently as possible, which often involves traveling in a vehicle. These two needs can often be at odds with each other, but while the vehicle usually wins today, the balance is starting to shift.

Many cities, like Boston and Toronto, have published Complete Streets Guidelines to promote design standards for pedestrians, bicycles, transit, and public space. In 2017, NACTO released its Blueprint for Autonomous Urbanism to “proactively guide the [self-driving vehicle] technology to prioritize people-first design.” Sidewalk Labs aims to build on these ideas by asking: “Instead of teaching self-driving vehicles to operate on today’s streets, can we take advantage of new technologies to fundamentally redesign the street?”

This living document proposes design principles that strive to harness these advances to create safer and more flexible streets. These principles will be updated periodically based on collaboration with city planners, engineers, mobility providers, and technology companies — and by Sidewalk Labs itself, as we test designs in prototype and pilot environments.

Image showcases a street with wide lanes of traffic that are difficult for pedestrians to cross. There is lots of pavement, but no bike lanes. Environment is uninviting for pedestrians and cyclists, and a significant amount of space is devoted to parking.
Photo Credit: “Rockaway Blvd,” by Tdorante10 is licensed under a Creative Commons Attribution-Share Alike 4.0 International License

Streets Today.

Cities often have the worst of both worlds when it comes to street design: top speeds that create safety risks, but average speeds that frustrate everyone. The solution is often to make streets wider by adding lanes and buffers, but that approach can do more harm than good.

Cities often design streets to be safe by making them wide, but wide streets cause speeding.

Streets today are designed to allow vehicles to move quickly. But this decision requires streets to be designed defensively as well — because speed kills. As a result, engineers design wider lanes to account for drivers who drift or veer, and they design buffer spaces like shoulders, medians, and street-parking areas to try to improve pedestrian and cyclist safety. But they are not safe; more than 6,700 pedestrians and cyclists died on streets in the United States in 2017 due to automobile crashes.(1) Neither pavement markings nor bollards are enough to protect vulnerable bicycles and pedestrians — and certainly not enough to make them feel comfortable.

This approach doesn’t help move people, either.

Despite being engineered for speed, today's streets are often congested — and frustratingly slow. Congestion caused by double-parking and uneven distribution of traffic volume across the day leads to lower average speeds overall. In 2018, nearly every major U.S. city recorded a downtown last-mile travel speed below 20 mph.(2) In downtown Toronto, the speed limit is 40 km/h (~25 mph), but most vehicles travel at an average speed of 24 km/h (~15 mph) — and some much, much slower than that.(3) As a result, drivers and passengers are still frustrated with long, stop-and-go commutes.

One common solution is to add even more lanes, but this leads to streets that can feel empty, because they’ve been designed for the worst-case traffic scenario.

In an effort to accommodate more vehicles, engineers have defaulted to calculating the space needed to handle peak, rush-hour demand. The result is acres of pavement that are empty at all other times and are neither pleasant to walk around nor conducive to the types of welcoming urban spaces that encourage street life. Part of the reason engineers feel the need to plan for worst-case traffic scenarios is because curbs and pavement markings are set rigidly into place and unable to adapt to changing needs.

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The Opportunity.

Technology is not a cure-all solution to mobility challenges. But it offers the chance to fundamentally redesign our street system with narrower, safer streets that still get people where they need to go.

Autonomous shuttle image features a Navya autonomous shuttle. The vehicle is 2.65 meters tall and 4.75 meters wide; it can fit 15 passengers.
Photo Credit: “Navya Autonom Shuttle - Bethelet (Genas)” by Anthony Levrot is licensed under a Creative Commons Attribution ShareAlike 2.0 Generic License
Connected and autonomous vehicles (CAVs) can be required to follow speed limits and can operate in narrow streets where lanes may appear, disappear, or change direction.

Connected vehicles are vehicles driven by people that receive warnings on speed limits, potential conflicts, hazardous conditions, and other detailed information to improve safety. Autonomous or self-driving vehicles are able to ingest this information and have the vehicle itself respond, without a person driving.

Together, CAVs can be expected to follow speed limits, stay out of areas that are restricted, and obey rules of interaction with cyclists and pedestrians. These advances also apply to e-bikes and e-scooters that could be hard-coded to remain in vehicle or bike lanes. Similarly, CAVs could safely travel on narrower streets that are prioritized for transit, bicycles, and pedestrians, including pedestrians using wheelchairs or other assistive devices.

Dynamic pavement image shows a cross walk that uses panels containing LED lighting. The panels create dynamic road markings using both texture and color.
Photo Credit: Flowell dynamic pavement photography courtesy of Colas and photographer Joachim Bertrand.
Dynamic (LED-embedded) pavement and moveable street furniture can help adapt the number of lanes, the width of the sidewalk, and even the direction of the street, meaning that a narrower street can serve multiple uses based on demand.

The operation and character of a street can change daily when raised concrete curbs can be removed in favor of dynamic pavement and moveable street furniture. Several companies have started to experiment with dynamic pavement, which embeds LEDs into the surface to change the color and shapes of markings. These design features can be used to create travel lanes, bike lanes, transit lanes, or pick-up/drop-off zones. They can also be used to change a lane’s travel direction, providing more flexibility than a fixed, grade-separated curb ever could.

Such a dynamic allocation of space allows for a potential reduction of vehicle space, creating safer crossing distances for pedestrians; providing a more pleasant walking and cycling environment; improving the travel experience for pedestrians using strollers, wheelchairs, or other types of wheels; and naturally slowing down vehicles that are used to wide lanes.

Digital signage image depicts a curb parking sign with a digital interface that allows parking rules and restrictions to change in real-time throughout the day.
Photo Credit: Digital signage photography courtesy of Mercury Innovation Pty Ltd.
Sensors, digital signage, and integrated navigation apps and fleets can communicate real-time information on speed limits and lane closures.

Spatial occupancy sensors can give cities a better understanding of street conditions by generating real-time feedback like curb space availability or congestion on a given road. That information can be communicated directly to travelers through digital signage or via integration with vehicles and navigation apps.

It can also identify patterns that emerge over time, information that is critical to urban planners and traffic engineers. For example, BriskLUMINA sensor applications have helped planners in Atlanta and Pittsburgh identify intersections with higher than normal risk of pedestrian injury. Other cities have used sensors to help optimize traffic light timing.(4)

An image of a greenwave shows a cyclist biking down a street next to a series of green LED lights. The lights set the pace a cyclist needs to travel in order to avoid being stopped at a red light.
Photo Credit: Greenwave photography courtesy of SWARCO.
Traffic management tools can recommend changes to lanes, speed limits, and pricing to maintain person-throughput or meet policy goals, such as Vision Zero.

Traffic management tools can make the most of roadway space and increase “person throughput,” or the total amount of people traveling through an intersection, across all modes (not just vehicles). These tools include low-cost sensors, edge computing capabilities, machine-learning simulation models, and adaptive traffic signals that can adjust green times to optimize flow or prioritize certain modes. Together, these tools can form a mobility management system that can adapt to real-time street conditions by reallocating lanes and adjusting signal timings to keep all modes moving — and safe.

One promising management advance is the bicycle “green wave,” which works with adaptive traffic signals to give cyclists a premium experience. LED indicators embedded at the edge of a bicycle lane can light up in front of cyclists to form a moving green segment. The segment sets the ideal travel speed for cyclists, so they arrive at intersections when the traffic signal is green. Information on speed and green times can be communicated by fleets and navigation apps.

The Principles

With these new capabilities in mind, Sidewalk Labs developed an overlapping network of streets, each designed to prioritize certain modes, that can improve safety and the public realm without restricting movement.

Principle 1. Tailor streets for different modes

New capabilities make it possible to design streets that prioritize certain modes, instead of aiming to accommodate all uses at all times of day. Laneways prioritize pedestrians while Accessways prioritize cyclists. Transitways give priority to public transit through dedicated lanes and signal priority. Boulevards are intended for all modes but primarily for vehicles.

Select a mode of transportation to view available streets.

Grid Illustration Image of a street grid made up of Boulevards and Transitways on the periphery and Laneways and Accessways intersecting throughout the interior. Next to the grid are icons of various modes of transportation, including an automobile, a light-rail train, a cyclist, a pedestrian, and an autonomous vehicle. After clicking an icon, the street grid lights up the streets that are available for the selected mode of transportation. While cyclists, pedestrians, and autonomous vehicles are allowed on every street, traditional vehicles and public transit are restricted to the periphery street. Boulevards Accessways Laneways BOULEVARD BOULEVARD BOULEVARD BOULEVARD ACCESSWAY ACCESSWAY ACCESSWAY ACCESSWAY ACCESSWAY ACCESSWAY LANEWAY LANEWAY LANEWAY LANEWAY LANEWAY LANEWAY LANEWAY LANEWAY

Principle 2. Separate streets by speed

CAVs and digital navigation tools enable faster street types to focus on moving people with vehicles and public transit, and slower street types to provide a safe and active environment for cycling and walking. Laneways operate at fast walking speed of 4 mph (8 km/h) while Accessways operate at 14 mph (22 km/h) - a brisk speed for most urban cyclists. Boulevards and Transitways have a speed limit of 25 mph (40 km/h), which evidence shows is the maximum speed consistent with pedestrian safety.

Image of a street grid made up of Boulevards and Transitways on the periphery and Laneways and Accessways intersecting throughout the grid. On the grid are indicators for origin and destination points.
By moving the origin and destination points to different intersections on the grid, the animation will show the best traveling path for a biker, a pedestrian, and an autonomous vehicle.
The animation demonstrates that vehicles will prefer to travel along Boulevards because of their higher speed limits, even though the route may be a longer distance. Both cyclists and vehicles will avoid Laneways as much as possible, because of their low speed limits.

Principle 3. Incorporate flexibility into street space

Adaptable infrastructure and real-time traffic insight make it easy for lanes to become “dynamic,” serving different purposes across the day. Sidewalk Labs is exploring a concept we call the "dynamic curb" which could be reserved for vehicles or converted into public space, depending on priorities. Optimizing this space requires a management system to understand demand and congestion patterns at various times and can vary depending on local policy objectives.

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Principle 4. Recapture street space for the public realm, transit, bikes, and pedestrians

CAVs, adaptable infrastructure like dynamic pavement, and moveable street furniture enable cities to recapture space once devoted to parking and vehicles. This space can be reallocated to the public realm and high person-throughput modes, such as transit, while still enabling all travelers to get where they need to go.

A New Street Network.

Collectively, these principles enable the design of a new street network that can accommodate the same throughput as today’s streets while drastically improving safety and creating a robust public realm.

Image depicts a busy, active Boulevard. Two light rail trains travel in the street’s center lanes. Passengers at nearby stations prepare to board the trains. Both traditional vehicles and autonomous vehicles travel in two vehicle-only lanes. Cyclists travel in both directions in separated bike lanes. During peak hours, two dynamic lanes are used to accommodate passenger loading or unloading. During off-peak hours, the dynamic lane is used for additional pedestrian space. Pedestrians travel along outside lanes and cross the Boulevard at designated crosswalks. The street is surrounded by ground-floor retails shops.

Laneways

A technical drawing of a Laneway depicts pedestrians traveling in one center lane; autonomous vehicles traveling at low speeds also share the lane. The Laneway features pedestrian areas including benches and cafe tables along the outside of the street.
  1. 35 feet (11 meters) wide
  2. Summer block party
  3. Easy entrance access
Laneways are primarily pedestrian pathways where walking or strolling is pleasant. Cycling or slow vehicle travel is permitted at the designated speed limits to ensure pedestrian priority and discourage Laneway use for long-distance travel.
Learn more
Person-throughput capacity estimates Laneways with CAVs Local Road in a typical downtown
Speed limit 4 mph (8 km/h) 25-30 mph (40-50 km/h)
Typical average speed 4 mph (8 km/h) 15 mph (24 km/h)
In vehicles ~120 persons / hour ~200 persons / hour
On transit N/A N/A
On bikes ~400 persons / hour ~700 persons / hour
On foot ~2,250 persons / hour ~600 persons / hour
Total person-throughput ~2,770 persons / hour ~1,500 persons / hour

Accessways

A technical drawing of an Accessway depicts cyclists and autonomous vehicles traveling in two center lanes and two wide pedestrian lanes on the outside of the cyclists lanes. The Accessway also features green wave LED lighting alongside the cyclists lanes. Bike-share facilities are located alongside Accessway routes.
  1. 50 feet (16 meters) wide
  2. Saturday afternoon in summer
  3. Rush hour in winter
Accessways are narrower streets that prioritize micromobility modes like bikes and scooters — when connected, Accessways form a bicycle network that rivals the travel time and convenience of transit and vehicles.
Learn more
Person-throughput capacity estimates Accessways with CAVs Collector in a typical downtown
Speed limit 14 mph (22 km/h) 25-30 mph (40-50 km/h)
Typical average speed 14 mph (22 km/h) 15 mph (24 km/h)
In vehicles ~850 persons / hour ~430 persons / hour
On transit N/A N/A
On bikes ~2,600 persons / hour ~700 persons / hour
On foot ~380 persons / hour ~200 persons / hour
Total person-throughput ~3,830 persons / hour ~1,330 persons / hour

Transitways

A technical drawing of a Transitway depicts light rail transit and autonomous vehicles traveling in two center lanes, cyclists traveling in both directions on the outside of the transit lanes, and two wide pedestrian lanes on the outside of the cyclists lanes. The Transitway also features dynamic loading bays that sit between the transit lanes and the cyclist lanes. When not used for loading, the bays can be used as cyclist lanes. Crosswalks are used to connect pedestrians to transit stops that sit next to the transit lanes.
  1. 85 feet (26 meters) wide
  2. Starts as a car-free corridor
  3. Allows CAVs
Transitways prioritize public transportation over all other modes, with emphasis given to light rail and dedicated bus lanes — linking the neighborhood to the city’s greater transit system.
Learn more
Person-throughput capacity estimates Transitways with CAVs Minor Arterial in a typical downtown
Speed limit 25 mph (40 km/h) 25-50 mph (40-80 km/h)
Typical average speed 25 mph (40 km/h) 15 mph (24 km/h)
In vehicles ~1,500 persons / hour ~850 persons / hour
On transit ~3,000 persons / hour N/A
On bikes ~1,400 persons / hour ~700 persons / hour
On foot ~280 persons / hour ~120 persons / hour
Total person-throughput ~6,180 persons / hour ~1,670 persons / hour

Boulevards

A technical drawing of a Boulevard depicts light rail transit traveling in two center lanes, automobiles traveling in both directions on the outside of the transit lanes, cyclists traveling in both directions on the outside of the automobile lanes, and two wide pedestrian lanes on the outside of the cyclists lanes. The Boulevard also features dynamic loading bays that sit between the cyclist lanes and the pedestrian lanes. When not used for loading, the bays can be used as pedestrian lanes. Crosswalks are used to connect pedestrians to transit stops that sit next to the transit lanes.
  1. 100 feet (31 meters) wide
  2. Optimized for expanded public realm
  3. Optimized for through movement
Boulevards accommodate all modes, but are geared towards moving people efficiently without sacrificing safety.
Learn more
Person-throughput capacity estimates Boulevards with CAVs Major Arterial in a typical downtown
Speed limit 25 mph (40 km/h) 25-50 mph (40-80 km/h)
Typical average speed 25 mph (40 km/h) 15 mph (24 km/h)
In vehicles ~2,000 persons / hour ~1,300 persons / hour
On transit ~3,000 persons / hour N/A
On bikes ~1,400 persons / hour ~700 persons / hour
On foot ~250 persons / hour ~120 persons / hour
Total person-throughput ~6,650 persons / hour (3,650 persons / hour w/o transit) ~2,120 persons / hour
Image depicts an Accessway. Cyclists, including one person driving a cargobike, travel along the two center lanes. Cyclists are biking alongside a greenwave--green LED lights that light up to indicate the optimal biking speed. Some AVs are traveling along the Accessway too, but are traveling at the same speed as cyclists. Pedestrians walk in outer lanes. The Accessway features greenery and retail shops on both sides of the street.

Streets for an Integrated Mobility System

The Street Design Principles should be considered just one part of an overall mobility strategy. Even the best-designed street network can only realize its full potential as part of an integrated transportation system with many trip options.

For our Sidewalk Toronto project, this overall mobility strategy is anchored in the extension of a high-capacity light rail transit network — knowing that public transit is by far the most efficient way to connect people and jobs across dense urban areas.

This strategy continues with expanded walking and cycling infrastructure to encourage the use of active transportation modes, with, bike-share, scooter-share, and other low-speed vehicle options playing an increasing role.

Finally, new mobility options — such as carshare, taxi, and ride-hail services — can help reduce the need for residents or workers to own a car while still facilitating vehicle trips.

Sidewalk Labs recognizes that a manager (often a city department or agency) is required for all these types of streets and trip options to work in concert. It is important that this manager be empowered to use tools like regulation changes, pricing, and adaptive traffic signal management to achieve the policy goals and performance targets that are set.

The Street Design Principles are the foundation for this integrated mobility system, providing the infrastructure and framework for cities to balance the need to move people with the re-emergence of streets as vital community space.

Video features dynamic pavement prototype installed at Sidewalk Toronto’s 307 campus. LED light panels are installed within hexagonal pavers. The lights change color to indicate different street uses.
Prototype of Kinaptic LightPavers installed at Sidewalk Toronto’s 307 campus.

Next Steps.

In the coming year, we'll test our principles — and the designs and technologies that enable them — through real-life prototypes in the United States, always seeking feedback from experts and communities.

The goal of these prototypes will be to gauge how drivers, pedestrians, and cyclists react to these designs and, in particular, the dynamic elements.

Over the course of 2018, Sidewalk Labs hosted a series of co-design sessions, events, and workshops in order to engage with the accessibility community and co-create our accessibility principles with them. We remain committed to these principles, which will evolve as we receive more feedback, and we will continue to work with the accessibility community to ensure our street designs work for all people with lived experience of disability.

We’ll have a better understanding of how dynamic pavement, bicycle LEDs, and sensor hardware work — and begin to test operational, maintenance, and life-cycle costs.

We’ll bring these elements together in order to test for safety, operability, and throughput.

Most importantly, we’d like to hear from you — the mobility engineers, planners, advocates, providers, disrupters, and enthusiasts. Let us know what you think, and help us drive towards the next version of these designs.