Permanent project revision

Vision Zero Boston: 25 mph default limit and open crash records

Revision 2026-08-20-source-dates · effective 2026-07-26

Superseded. A later revision exists: 2026-08-20-source-dates-corrected →

unreviewed

Created the first structured Evidence Passport with 1 claim and 13 source dossiers.

sha256:6a11041351ee855ab648d089a3dd20aa998d2d62b24ae574bbda086fc28fc800

All revisions → Current entity page →

Change set

add /evidencePassport — Added claim-level evidence mapping and source dossiers.
add /revisionHistory — Established a permanent, hash-addressed baseline revision.

1: of 1 claims mapped
13: source dossiers
6: publication dates recorded
1: archives linked
0: exact locators
0: content captures hashed

Claims, one by one

The text below is copied verbatim from the published record. Each claim names the source dossiers that carry it; caveats stay attached to the claim they qualify.

Claim 1 clm-8708cd5a91cece5a quantitative

mean speeds fell 0.3 percent, which was not statistically significant (p=0.065), while the odds of a vehicle exceeding 25, 30 and 35 mph fell 2.9, 8.5 and 29.3 percent

Published field: impact · verbatim
Mapping: mapped · no interpretation or interpolation added by this passport
What the mapping says: The study compared speeds at Boston sites with control sites in Providence, Rhode Island, before and after the limit change.
Caveat: The programme's own goal is not on track — the city says Boston still sees 10+ traffic deaths and thousands of injuries a year.

Sources carrying this claim

Hu & Cicchino, Injury Prevention 2020;26:99-102 (peer-reviewed)

Source dossiers and revision state

This layer records what is known about each source, what is still missing, and the exact snapshot this page is rendering. A missing date, archive or hash stays visible as missing.

unreviewed Revision 2026-08-20-source-dates effective 2026-07-26 · created 2026-08-20

Awaiting operator and domain-expert review; publication of this revision implies neither.

sha256:6a11041351ee855ab648d089a3dd20aa998d2d62b24ae574bbda086fc28fc800

Revision history → Permanent version link → Machine-readable record → Evidence Constitution →

1: of 1 claims mapped
13: source dossiers
6: publication dates recorded
1: archives linked
0: exact locators
0: content captures hashed

Governance facts carried by the record

Operator: City of Boston — Boston Transportation Department (Streets Cabinet), with Boston EMS and the Department of Innovation and Technology on the data
Actor types: city-government
Funding model: public
Funding description: City of Boston capital and operating budget
Cost: Traffic calming funded at $15M in the enacted FY26 budget and $13M in the FY27 proposal
Ownership: Not recorded
Decision rights: Not recorded
Exit conditions: Not recorded

13 source dossiers

City of Boston — 25 in Boston (authority) boston.gov · background

Open original source ↗

Stable source ID: src-277ee9eeda224d8f
Publisher: Name not classified · boston.gov
Type / language: web-page · language not classified
Published: Not recorded
Updated: 2025-10-30
Source last checked: No source-level check date
Record last verified: 2026-07-26
Dossier created: 2026-08-20
Retrieved copy: No local capture recorded
Archive: No archived copy linked
Content hash: No captured content hash
Locator: Open the recorded source note
Primary for the date and the scope limit. The default limit took effect 'January 9, 2017' on city-owned streets without posted limits. Also carries the jurisdictional caveat in the city's own words: 'This change only affects roads the City owns. Please pay attention to posted signs on state-owned roads.' The page does not name the enabling statute; that is sourced separately.
Descriptive only — not page/paragraph exact
Claims linked: Background source; no baseline claim points here

M.G.L. c. 90 §17C — 25 mph in thickly settled districts (statute) malegislature.gov · background

Open original source ↗

Stable source ID: src-44b208c02944e47d
Publisher: Name not classified · malegislature.gov
Type / language: web-page · language not classified
Published: Not recorded
Updated: Not recorded
Source last checked: No source-level check date
Record last verified: 2026-07-26
Dossier created: 2026-08-20
Retrieved copy: No local capture recorded
Archive: No archived copy linked
Content hash: No captured content hash
Locator: Open the recorded source note
The enabling authority. The Municipal Modernization Act of August 2016 let municipalities that accept §17C lower the statutory limit from 30 to 25 mph in thickly settled or business districts without MassDOT approval; Boston accepted it citywide, effective 9 January 2017. MassDOT's guidance page on speed limits in thickly settled districts covers the same mechanism.
Descriptive only — not page/paragraph exact
Claims linked: Background source; no baseline claim points here

Hu & Cicchino, Injury Prevention 2020;26:99-102 (peer-reviewed) iihs.org · 1 linked claim

Open original source ↗

Stable source ID: src-e87a8c0c4939d965
Publisher: Name not classified · iihs.org
Type / language: web-page · language not classified
Published: Not recorded
Updated: Not recorded
Source last checked: No source-level check date
Record last verified: 2026-07-26
Dossier created: 2026-08-20
Retrieved copy: No local capture recorded
Archive: Open archived copy ↗ · 2026-06-08
Content hash: No captured content hash
Locator: Open the recorded source note
The controlled evaluation the entry rests on. Method: vehicle speeds collected 'at sites in Boston where the speed limit was lowered, and at control sites in Providence, Rhode Island, where the speed limit remained unchanged, before and after the speed limit change in Boston', with a log-linear model for mean speed and separate logistic models for exceedance. Result, verbatim: 'The speed limit reduction was associated with a 0.3% reduction in mean speeds (p=0.065), and reductions of 2.9%, 8.5% and 29.3% in the odds of vehicles exceeding 25 mph, 30 mph and 35 mph, respectively.' Neither the abstract nor the IIHS record states the number of sites. Note the authors are staff of the Insurance Institute for Highway Safety, an insurance-industry-funded body; the paper itself is peer-reviewed in a BMJ journal.
Descriptive only — not page/paragraph exact
Claims linked: clm-8708cd5a91cece5a

IIHS — plain-language summary of the same study (research body) iihs.org · background

Open original source ↗

Stable source ID: src-f897902133055f3b
Publisher: Name not classified · iihs.org
Type / language: web-page · language not classified
Published: 2018-08-28
Updated: Not recorded
Source last checked: No source-level check date
Record last verified: 2026-07-26
Dossier created: 2026-08-20
Retrieved copy: No local capture recorded
Archive: No archived copy linked
Content hash: No captured content hash
Locator: Open the recorded source note
Second reading of the same numbers: 'After Boston lowered the default speed limit to 25 mph, the estimated odds of a vehicle exceeding 35 mph fell 29.3%', with 8.5 percent for 30 mph and 2.9 percent for 25 mph, Providence as control, measured around the 9 January 2017 change, at arterial, collector and local road sites.
Descriptive only — not page/paragraph exact
Claims linked: Background source; no baseline claim points here

Analyze Boston — Vision Zero Crash Records dataset (authority, open data) data.boston.gov · background

Open original source ↗

Stable source ID: src-49e78972da8619cf
Publisher: Name not classified · data.boston.gov
Type / language: web-page · language not classified
Published: 2018-05-01
Updated: Not recorded
Source last checked: No source-level check date
Record last verified: 2026-07-26
Dossier created: 2026-08-20
Retrieved copy: No local capture recorded
Archive: No archived copy linked
Content hash: No captured content hash
Locator: Open the recorded source note
The data layer, and the licence answer: 'Open Data Commons Public Domain Dedication and License (PDDL)'. Records run 1 January 2015 through 30 June 2026, updated monthly. The source is EMS, not police: 'Motor Vehicle Accidents (MVAs) provided in this dataset are Boston EMS incidents with a documented patient encounter that were identified as an MVA during the 9-1-1 call taking process, by crews on scene, or incidents where the injury cause is documented as related to an MVA', compiled by the Department of Innovation and Technology from the Computer-Aided Dispatch (911) system. The page also flags a break in the series: 'In June of 2024, Boston EMS transitioned to a new patient record system… Differences in MVA rates before and after June 2024 are reflective of this new reporting methodology and should not be interpreted as a change in motor vehicle incidents.'
Descriptive only — not page/paragraph exact
Claims linked: Background source; no baseline claim points here

Analyze Boston — Vision Zero Fatality Records dataset (authority, open data) data.boston.gov · background

Open original source ↗

Stable source ID: src-d9c5e1dcd3dfaad0
Publisher: Name not classified · data.boston.gov
Type / language: web-page · language not classified
Published: 2018-07-23
Updated: Not recorded
Source last checked: No source-level check date
Record last verified: 2026-07-26
Dossier created: 2026-08-20
Retrieved copy: No local capture recorded
Archive: No archived copy linked
Content hash: No captured content hash
Locator: Open the recorded source note
The other half of the split: fatalities are 'compiled by the Department of Innovation and Technology from the 911 system and verified by Boston Police Department', 1 January 2015 to present, monthly, also under the Open Data Commons Public Domain Dedication and License (PDDL).
Descriptive only — not page/paragraph exact
Claims linked: Background source; no baseline claim points here

Vision Zero Crash Records Map — about page (authority) apps.boston.gov · background

Open original source ↗

Stable source ID: src-2091caf23d60f367
Publisher: Name not classified · apps.boston.gov
Type / language: web-page · language not classified
Published: Not recorded
Updated: Not recorded
Source last checked: No source-level check date
Record last verified: 2026-07-26
Dossier created: 2026-08-20
Retrieved copy: No local capture recorded
Archive: No archived copy linked
Content hash: No captured content hash
Locator: Open the recorded source note
What the public map does and does not show. Records cover 'date, time, location, and type of crash for incidents requiring public safety response which may involve injuries or fatalities', but 'do not indicate the severity of specific crashes or whether medical care was provided'; 'Each incident is included only once regardless of the number of individuals involved'; the timestamp is when response was dispatched, 'not the crash itself'; and the city states errors may be present and the information may not be complete.
Descriptive only — not page/paragraph exact
Claims linked: Background source; no baseline claim points here

City of Boston — Vision Zero (authority) boston.gov · background

Open original source ↗

Stable source ID: src-954238c960d30854
Publisher: Name not classified · boston.gov
Type / language: web-page · language not classified
Published: Not recorded
Updated: 2026-07-27
Source last checked: No source-level check date
Record last verified: 2026-07-26
Dossier created: 2026-08-20
Retrieved copy: No local capture recorded
Archive: No archived copy linked
Content hash: No captured content hash
Locator: Open the recorded source note
The goal and the shortfall in the same place: the programme aims to 'eliminate fatal and severe traffic crashes in the City by 2030', while the city reports it 'currently experiences 10+ fatalities, hundreds of pedestrian and cyclist injuries, and thousands of driver injuries on city streets every year'. Also hosts the injury crash map and the by-mode dashboards.
Descriptive only — not page/paragraph exact
Claims linked: Background source; no baseline claim points here

City of Boston — Neighborhood Slow Streets (authority) boston.gov · background

Open original source ↗

Stable source ID: src-6ef58f331c874ab0
Publisher: Name not classified · boston.gov
Type / language: web-page · language not classified
Published: Not recorded
Updated: 2025-10-30
Source last checked: No source-level check date
Record last verified: 2026-07-26
Dossier created: 2026-08-20
Retrieved copy: No local capture recorded
Archive: No archived copy linked
Content hash: No captured content hash
Locator: Open the recorded source note
The 20 mph layer: traffic calming built in 15 neighbourhoods, where 'the speed limit on its residential streets will be 20 mph'. Piloted in the Talbot Norfolk Triangle in Dorchester and Stonybrook in Jamaica Plain in late 2017; renamed Safety Surge in 2023. No verified count of formally designated statutory 20 mph safety zones was found, so none is claimed.
Descriptive only — not page/paragraph exact
Claims linked: Background source; no baseline claim points here

Streetsblog Massachusetts — Safety Surge announcement, May 2023 (press) mass.streetsblog.org · background

Open original source ↗

Stable source ID: src-f3911821984696a8
Publisher: Name not classified · mass.streetsblog.org
Type / language: web-page · language not classified
Published: 2023-05-22
Updated: Not recorded
Source last checked: No source-level check date
Record last verified: 2026-07-26
Dossier created: 2026-08-20
Retrieved copy: No local capture recorded
Archive: No archived copy linked
Content hash: No captured content hash
Locator: Open the recorded source note
What changed under the administration that took office in November 2021: the slow-streets programme was rebuilt as Safety Surge with more than $12 million in the FY24 budget, roughly 10 speed-hump zones and 25 to 30 intersection redesigns a year, prioritised on crash history and demographics.
Descriptive only — not page/paragraph exact
Claims linked: Background source; no baseline claim points here

Streetsblog Massachusetts — FY27 budget cuts, April 2026 (press) mass.streetsblog.org · background

Open original source ↗

Stable source ID: src-ac9f6d10e15133b6
Publisher: Name not classified · mass.streetsblog.org
Type / language: web-page · language not classified
Published: 2026-04-22
Updated: Not recorded
Source last checked: No source-level check date
Record last verified: 2026-07-26
Dossier created: 2026-08-20
Retrieved copy: No local capture recorded
Archive: No archived copy linked
Content hash: No captured content hash
Locator: Open the recorded source note
The currency counterweight. Safety Surge falls from '$15 million in enacted FY26 budget' to '$13 million in FY27 proposal', and more than a dozen street-safety capital lines go to zero, including Roxbury Resilient Transportation Corridors ($32.5M to $0), Dedicated Bus Lanes ($13.5M to $0) and Commonwealth Avenue Phases 3, 3B and 4 ($13.5M to $0). Delivery, not just budget, is the issue: 'Boston's Streets Cabinet spent only $450,000 on speed humps in the past year – less than 10 percent of what the FY26 budget had proposed.'
Descriptive only — not page/paragraph exact
Claims linked: Background source; no baseline claim points here

LivableStreets Alliance decade review, June 2026, via Streetsblog Massachusetts (independent) mass.streetsblog.org · background

Open original source ↗

Stable source ID: src-4f38135112fb81cd
Publisher: Name not classified · mass.streetsblog.org
Type / language: web-page · language not classified
Published: 2026-06-26
Updated: Not recorded
Source last checked: No source-level check date
Record last verified: 2026-07-26
Dossier created: 2026-08-20
Retrieved copy: No local capture recorded
Archive: No archived copy linked
Content hash: No captured content hash
Locator: Open the recorded source note
The only whole-programme assessment found outside the city; no municipal auditor review exists. The advocacy research group analysed a decade of crash data across Boston, Cambridge and Somerville, finding progress that was 'uneven at times'. On Boston specifically: 'Boston, by contrast, focused its resources on streets with the highest rates of injuries', citing Tremont Street, Centre Street in West Roxbury and the Common and Public Garden roadways. The report's standout is Somerville, with no fatal crashes since 2022 — not Boston.
Descriptive only — not page/paragraph exact
Claims linked: Background source; no baseline claim points here

Boston Region MPO — High-Injury Network methodology (regional authority) ctps.org · background

Open original source ↗

Stable source ID: src-f60aa6949538a2cf
Publisher: Name not classified · ctps.org
Type / language: web-page · language not classified
Published: Not recorded
Updated: Not recorded
Source last checked: No source-level check date
Record last verified: 2026-07-26
Dossier created: 2026-08-20
Retrieved copy: No local capture recorded
Archive: No archived copy linked
Content hash: No captured content hash
Locator: Open the recorded source note
Confirms what makes Boston's series unusual and where the city's writ ends. Regional high-injury analysis draws on MassDOT's IMPACT portal, whose 'crash database currently relies on information from police reports, but some cities, like Boston, also collect data from city EMS services'. It also records that roads on the network are owned variously by municipalities, MassDOT or the Department of Conservation and Recreation. No source gives a Boston-specific share of state-owned roads, so the entry claims none.
Descriptive only — not page/paragraph exact
Claims linked: Background source; no baseline claim points here

Known limits of this passport

Publisher names and source languages have not yet been classified; domains are recorded without guessing.
Existing source notes are descriptive locators, not page- or paragraph-exact citations.
A missing archive, publication date or content hash is shown as null rather than inferred.
The project-level evidence grade ranks the strongest source in the entry; it is not a truth score for every claim.