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Signs that say "On most Cambridge Streets, speed limit 20" in multiple languages.

Speed Limits in Cambridge

As a part of our Vision Zero efforts, we reduced the speed limit to 20 mph on most Cambridge Streets.

On posted streets, the speed limit is 20 mph.

Reducing driving speeds from 25 mph to 20 mph helps make Cambridge safer for people of all ages and abilities walking, biking, and driving on our streets. Small differences in travel speeds have a big impact on the outcomes of crashes. The graphic below shows the likelihood of severe or fatal injury for pedestrians struck by drivers traveling at various speeds.

Likelihood of serious or fatal injury for pedestrians struck by drivers at various speeds. 17% at 20 mph, 30% at 25 mph, 47% at 30 mph

Likelihood of severe or fatal injury for pedestrians struck by drivers traveling at these speeds.1

Show your support

We all share responsibility for ensuring that Cambridge is a safe place for everyone traveling on our streets. Here are a few ways to show your support:

  • Be aware of your speed. Drive at or below 20 mph. You can help save lives. If you crash, you’re less likely to cause serious injury or death.
  • Help spread the word. Talk with your family, neighbors, and friends about the speed limit changes.
  • Stop by our office to get a 20 mph button, sticker, or magnet.
  • Join the Vision Zero Cambridge email list.

Default (statutory) speed limits versus posted speed limits

The State rules for speed limits allow a minimum default (statutory) speed limit of 25 mph in Cambridge, or any other thickly settled area. They also require that signs be posted on each street that does not have the default (statutory) speed limit of 25 mph. This means that reducing the speed limit to 20 mph on most Cambridge streets required the installation of a lot of signs.

This work followed the reduction of the default speed limit from 30 mph to 25 mph in December of 2016. It also built off work done in early 2018 to decrease speed limits to 20 mph in the city’s five squares. These speed limit changes were made possible by the State's 2016 Municipal Modernization Act. Chapter 90, Section 18B of the Massachusetts General Laws allows the Traffic, Parking, and Transportation Department Director to establish 20 mph safety zones in the interest of public safety.

20 mph streets

On smaller, primarily local-access streets the speed limit is 20 mph. Larger, arterial roads will still have a speed limit of 25 mph, unless otherwise posted. When in doubt, go 20 mph. The map below shows street segments that have a 20 mph speed limit and the approximate location of 20 mph safety zone signs. White and yellow signs have been installed.


Sign installation

The signs were installed by a contractor. Work started in East Cambridge and proceeded across the city to the west.

Sign locations

In accordance with State rules, signs are posted at the beginning of every street that has a 20 mph speed limit. This does not mean that signs are posted on each individual block that makes up a street. Two-way streets have at least one sign in each direction and one-way streets have at least one sign. Signs are also sited at locations where they are necessary due to street direction changes. Additional signs have been sited at intersections with major streets to provide more clarity around which streets have 20 mph speed limits.

Example: Sciarappa St, in East Cambridge, spans from Monsignor O'Brien Highway to Charles Street. It crosses one arterial road, Cambridge St. Sciarappa Street from Monsignor O'Brien Highway to Winter St is one way, northbound. Sciarappa Street from Winter Street to Charles Street is two way. A sign on Sciarappa Street near the intersection of Winter Street covers the entire southbound direction, all the way to Charles Street. A sign on Sciarappa St near the intersection of Charles Street covers the entire northbound direction, all the way to Monsignor O'Brien Highway. Two additional signs on Sciarappa, on either side of the intersection with Cambridge Street, serve as additional reminders for people coming off of Cambridge St.


Many people are already traveling at or below 20 mph on our streets. Signs installed around the city serve as a reminder of our lower speed limits. The Cambridge Police Department uses a data-driven approach to conduct regular traffic enforcement across the city, including in places that already have 20 mph speed limits, such as school zones and squares. They prioritize strategic enforcement in areas that have seen a large number of crashes and regularly conduct proactive enforcement at specific times and locations based on crash analyses conducted by the City.


To begin to understand the effectiveness of posting a reduced 20 mph speed limit for lowering motorist speeds, Toole Design performed a study of the vehicle speeds using data collected before and after the City’s speed limit reductions.

Read the Memo


1Sources: Tefft, Brian C. Impact Speed and a Pedestrian’s Risk of Severe Injury or Death, AAA Foundation for Traffic Safety, Washington DC, September, 2011

Page was posted on 10/28/2019 9:22 AM
Page was last modified on 10/5/2023 10:14 AM
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