Massachusetts 20mph Safety Zones

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City of Cambridge

Cambridge has implemented 20mph speed zones through much of the city. This process involves installing 660 20mph speed limit signs.

As a part of our Vision Zero efforts, we’re reducing 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 will help 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.

Cambridge 20mph Safety Zone web page

https://www.cambridgema.gov/Departments/trafficparkingandtransportation/speedlimitsincambridge

GIS map of 20mph Safety Zones

https://cambridgegis.maps.arcgis.com/apps/Embed/index.html?webmap=cc9ff2d6b53e4877a4c7e5fb8c8d1a19&extent=-71.172,42.3505,-71.052,42.4053&zoom=true&scale=true&search=true&searchextent=true&legend=true&disable_scroll=false&theme=light

Letter to Cambridge City Council from Transportation Director

http://rwinters.com/council/020419M4b.pdf

Mass. General Law Ch. 90 Section 18B governing 20mph Safety Zones

Section 18B. (a) Notwithstanding section 18 or any other general or special law to the contrary, the city council, the transportation commissioner of the city of Boston, the board of selectmen, park commissioners, a traffic commission or traffic director of a city or town that accepts this section in the manner provided in section 4 of chapter 4 may, in the interests of public safety and without further authority, establish designated safety zones on, at or near any way in the city or town which is not a state highway, and with the approval of the department if the same is a state highway. Such safety zones shall be posted as having a speed limit of 20 miles per hour.

MassDOT guidance on Safety Zones

https://www.town.plympton.ma.us/sites/g/files/vyhlif1091/f/uploads/procedures_for_speed_zoning_02-2017.pdf#page=23

Speed limit reduction has worked in Massachusetts

https://aashtojournal.org/2018/08/31/studies-say-lower-speed-limits-will-help-improve-roadway-safety/

…and in other locations

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I think that’s wonderful. AT the same time, I recall when Nicole said to us at a TAG meeting when the topic came up, that the 20mph is not enforceable unless (what was the number?) something like 50% of the cars were regularly travelling at that speed.

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Traditionally, prevailing speed was 85%. But that wasn’t just about enforcement, that’s because the 85th percentile was use to determine the speed limit.

Is 20mph now enforceable? If not, what’s the point?

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it is enforceable because it is a statutory limit, so enforced at 30mph in standard practice

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The 2012 Bicycle Plan called for a complete network of bicycle infrastructure on these streets at a minimum: Beacon, Walnut, Centre, Chestnut, Washington, Lowell, Winchester, Dedham, Parker, Brookline, Nahanton, Watertown, Needham, Commonwealth, Lexington, Hammond, Hammond Pond (DCR), Lincoln, Woodward, Crafts, California, Waltham, Waverly, Ward, River, College, Greenwood St, Homer, Cabot, Church, Newtonville

Many of these streets have posted speed limits in some sections > 25 mph. (see Newton Traffic and Parking Regulations at https://www.newtonma.gov/home/showpublisheddocument?id=29801)

Some of these streets have no bicycle infrastructure at all, not even sharrows/signs, or the infrastructure starts and stops, or is on hold or planned for the future. Many of these streets could have contiguous bike lanes, or even quick build protected ones, if the city removed some parking.

These streets should ALL have temporarily reduced speed limits until there is “something” for bicycles, or permanently reduced speed limits if the only politically feasible infrastructure solution is sharrows/signs. Reducing speeds is a cost-effective way to make it safer for bicycles (and pedestrians, too).

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I am all in favor of a 20 mph city wide speed limit, BUT because of the posted speed limit exceptions listed in the Parking and Transportation Plan, it actually won’t help with the most dangerous streets, many of which don’t have bicycle infrastructure and are major bike routes. This may not be a complete list since I did it quickly…

THESE STREETS HAVE 30 MPH SECTIONS

Berkeley Street

Brandeis Road

Cabot Street

California Street

Centre Street

Charlesbank Road

Commonwealth Avenue

Concord Street

Cypress Street

Dedham Street

Elliot Street

Elm Street

Florence Street

Goddard Street

Grove Street

Greenlawn Avenue

LaGrange Street

Lexington Street

Lowell Avenue

Mill Street

Nahanton Street

North Street

Parker Street

Reservoir Avenue

River Street

Tremont Street

Tyler Terrace

Walnut Street

Waltham Street

Watertown Street

Waverley Avenue

Winchester Street

Woodland Road

THESE STREETS HAVE 35 MPH SECTIONS

Commonwealth Avenue

Nahanton Street

Tremont Street

Washington Street

Woodward Street

There are many more streets with 25 MPH SECTIONS that also won’t be affected by the 20 mph limit

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Molly:

If we create a safety zone, which is the ONLY way to get to 20 mph under state law without doing any further infrastructure work, that overrides the posted speed limits.

Jenn martin compiled both the law and the 20mph safety zone part of the law very nicely for Bike Newton. I thought it was pretty clear, and accurate.

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As I envision it, the 20mph zones would provide a “base layer” for the parts of Newton that we’re not likely to get bike facilities quickly if ever. We could spend a hundred millions dollars on infrastructure and not get bike lanes onto every neighborhood street - there isn’t geometry to do that anyway, and that wouldn’t benefit pedestrians to the extent we’d like.

In addition, we add safety zones on non-neighborhood streets where we have parks, schools, or other vulnerable populations. That’s actually a lot of additional areas. That sets a standard of behavior, but we know that it’s not alone going to provide the safety we need. We will need to combine additional traffic calming to reduce speeds. Lower speed limits and traffic calming go hand in hand, we just have the ability to move on the speed limits now.

That’s all independent of bicycling, and appeals to the larger ped/bike/family/elderly constituency. It does, however, provide a different way to look at a feasible bike plan: non-20mph routes should have bike facilities, as should 20mph zones with high bike traffic and on local through routes. I believe this is the better way to think about a bike plan, since bicycling should be safe and convenient on every street in Newton and not limited to designated streets in a plan.