How to Change Design Speeds, Save Lives, and Improve Our Cities

Designing for Speed is a weekly multi-part series exploring how speed is factored into the design of our streets, how it influences safety, and how it ultimately shapes our communities. This series is co-authored with Dustin Blacka design engineer working at the intersection of transportation, land use, and the built environment. Join the Beyond the Automobile mailing list to stay up to date with the series.


Speed is not the enemy, but it can be deadly and detrimental to our cities when applied improperly; it’s time we fixed that.

This article is a conclusion of a roller coaster of a series. So far we’ve covered the basics of design speed, how it is determined, and some of the negative consequences of high-speed design. Next we showcased Safe Systems as a pragmatic solution to picking a safe design speed. Finally, this post wraps up by returning to North America to showcase the resources and examples we have available here to design for the right speed.

A recently reconstructed main street in Renfrew, Ontario, designed to encourage slower vehicle speeds.

What Cities are Doing

  • The City of Ottawa has had a road safety program since 2003, with a budget of $4 million per year to implement targeted safety improvements and campaigns. As part of the program, Ottawa recently committed to designing all local streets to 30 km/h and is set to release its own design guidance for achieving that sometime in 2021
  • Washington D.C., Boston, New York, Seattle, and Montreal are among the many cities that have reduced their city-wide default speed limits to 25 mph or lower in an effort to increase roadway safety. Unless otherwise posted, these are the legal speed limits that travelers must obey in these cities. Early results from Seattle suggest that simply adding the new lower speed limit signs has reduced crashes from 20-40%. Other cities including Edmonton and Calgary have reduced speed limits only for residential streets
  • In 2019, York Region, a regional government in the Greater Toronto Area, released its Designing Great Streets Guidelines which include a recommendation to set the design speed equal to the posted speed for all low-speed streets up to 60 km/h (40 MPH). For streets 70 km/h and greater, the guide recommends designing for 10 km/h above the posted speed. This is similar to the recommendations of many other Complete Streets manuals.
A comparison of two approaches to determining design speed: conventional and context sensitive. Source: Toronto Complete Streets Guideline

What the Guidance Says

  • In 2017 a report from the US National Transportation Safety Board (NTSB) concluded that excessive speed is one of the most significant causes of both crashes and fatalities on U.S. roadways, accounting for over 10,000 deaths every year. One of the key recommendations of the report was to modernize how speed limits are set by using the Safe Systems approach, which accounts for all road users – not just people in cars
  • In 2020, NACTO followed up this recommendation with its guidance City Limits: Setting Safe Speed Limits on Urban Streets. The guidance recommends a new approach to setting speed limits, including:
    • Setting lower, city-wide speed limits (ex. 25 MPH on major streets and 20 MPH on minor streets)
    • Designating slow zones in sensitive areas
    • Setting corridor speed limits based on the context rather than simply the speed of the fastest drivers (i.e. the 85th percentile method)
  • In 2021, the State of Washington released a report, Injury Minimization and Speed Management Policy Elements and Implementation Recommendations that identifies strategies for achieving the state’s “Target Zero” highway safety plan. The report recommends establishing injury-minimizing target speeds for roadways, and implementing design changes where road operating speeds are above the targets
  • NACTO’s Designing for All Ages and Abilities document provides guidance on what traffic speeds and volumes are acceptable for different types of cycling facilities. Put another way, the guide communicates what the roadway speed should be lowered to in order to accommodate a full range of users. For example, lowering the speed of a low-volume residential street from 30 to 25 MPH may be enough to make it suitable for a “bicycle boulevard” where people comfortably ride in mixed traffic
NACTO’s recommended AAA cycling facility for each roadway context. Seen another way, the table shows the speed/volume combination that a street could be adjusted to in order to be suitable for a given type of cycling facility.

What You Can Do About it

Change does not happen overnight. Roads are only built once, they’re resurfaced every 20 years or so, and are rebuilt every 60 years. A systemic change can take an entire generation to be rolled out fully. Dutch cities provide an example of what North American cities could look like in 30 years – because the Dutch started implementing the Safe Systems approach precisely 30 years ago! Even today, they are still upgrading old intersections that look much more like their North American counterparts.

But change always starts somewhere. From these authors’ experience, here’s a high-level map to getting every community on the path to safe streets:

  • Step 1: Advocate for Safe Streets: in democratic society, all change starts with the people. Professionals and politicians are actors who respond to the needs of the public, so if road safety is a significant enough public concern, action is sure to follow. There are many ways to advocate for safer streets; examples include starting, joining or funding a community group (examples include Friends and Family for Safe Streets, Doctors for Safe Cycling, and HRM Safe Streets for Everyone), educating yourself on the data, and contacting your elected officials
  • Step 2: Endorse Vision Zero and identify goals for reducing collisions: When a City, state, or province officially endorses some sort of road safety vision (Vision Zero, Safe Systems, Target Zero, etc.), it confirms that safety is a political priority. In addition, many agencies have publicly endorsed the NACTO Urban Street Design Guide, signaling their commitment to safe street design
  • Step 3: Develop a road safety program with a dedicated budget and staff: Many cities have completed Step 2 but stumbled to go further. While endorsement is the first step towards change, it will yield nothing on its own. The next step is to establish a municipal road safety department will ensure that resources are available to analyze collisions and patterns, and giving them a meaningful budget will ensure they can implement tangible changes to reduce collisions
  • Step 4: Implement a Safe Systems approach to the design and construction of streets: A full-fledged commitment to Safe Systems is an order of magnitude more impactful than a road safety program, because a systematic implementation ensures that all roads are built safely for all users every time, not just when there is enough money in the road safety budget for retrofits. It requires all city groups to be aligned on a standardized commitment to safety, a difficult and lengthy process, but one that will pay huge dividends
A vigil held by Friends and Family for Safe Streets (FFSS) honouring victims of traffic violence. The group’s goal is to end traffic violence in Toronto. Source: Cycle Toronto

Breaking the Cycle

By now in the series, you should be familiar with the challenges of the “conventional” approach to design speed. Thus, we stand at a crossroads, with the opportunity for change.

Conventional Philosophy: design every road for a speed greater than what the posted speed will be, so that when motorists speed, they will pose less of a danger to the public. This approach assumes speeding is inevitable.

Safe Systems Philosophy: design every road for the speed you want people to drive based on the context, so that the majority of motorists will find it very uncomfortable to speed. This approach assumes speeding can be managed with design.

While the “conventional” approach may be an effective solution in rural areas, for roadways that connect destinations over long distances, it is largely inadequate for urban areas where other road users are present. Speed is not the enemy, but it can be deadly and detrimental to our cities when applied improperly; it’s time we fixed that.


This concludes the five-part series, Designing for Speed. Join the Beyond the Automobile mailing list to stay up to date with future posts. Special thanks to Dustin Black for collaborating on this post. Dustin is a design engineer working at the intersection of transportation, land use, and the built environment. Follow him on Twitter @EngineerDustin.

Don’t forget to check out the other posts in the Designing for Speed series below.

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