1001 Smart Cities

Permanent project revision

Green Line Train Protection System

Revision 2026-08-27-claims-and-sources · effective 2026-08-27

Superseded. A later revision exists: 2026-08-27-correction-run →

unreviewed

Created the first structured Evidence Passport with 8 claims and 11 source dossiers.

sha256:891b3e5a20d4f85f13bc2ba01fd47349044795185c61e6ad0c9e1c6e5cf22703
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.
8
of 8 claims mapped
11
source dossiers
8
publication dates recorded
0
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-55f11bbd7f6cccc3 descriptive
Boston's Green Line light rail has no system that enforces its signals or speed limits — operators simply obey them
Published field
snippet · verbatim
Mapping
mapped · no interpretation or interpolation added by this passport
What the mapping says
The NTSB report on the 2008 Newton collision records the precise defect: Green Line trains 'do not incorporate systems such as trip stops (mechanical arms or electrical inductors that slow or stop a train if the operator fails to respond)'. The operator's own project page describes the system being installed as one that alerts operators, not one that controls the train.
Caveat
ntsb.gov serves the report only as a PDF and the accident page as a JavaScript shell, so no locator string could be recorded from the source itself.

Sources carrying this claim

  1. NTSB — Collision of Two MBTA Green Line Trains, Newton, 28 May 2008 (RAR-09/02)
  2. MBTA — Green Line Train Protection System (operator project page)
Claim 2 clm-be6687f16b65ee7d quantitative
The MBTA is fitting ultra-wideband positioning that warns of overspeed and closing trains; the operator says 20 trains have been equipped so far
Published field
snippet · verbatim
Mapping
mapped · no interpretation or interpolation added by this passport
What the mapping says
The February 2025 board summary describes 'Piper's Cenelec SIL-4 Ultra-Wideband positioning technology to localize trains operating both at grade and in the underground central subway areas'. The project page states 'So far, 20 trains have been equipped with the new technology', and NBC10 Boston describes the sensors and the cab display.
Caveat
No claim-specific caveat recorded

Sources carrying this claim

  1. MBTA — Green Line Train Protection System (operator project page)
  2. MBTA Board of Directors — GLTPS-2 Procurement staff summary, 25 February 2025 (operator)
  3. NBC10 Boston — Here’s an exclusive look at the MBTA’s new train protection system on the Green Line (8 October 2025)
Claim 3 clm-9e704ffb5fe8ac43 quantitative
The NTSB recommended collision avoidance in 2009
Published field
snippet · verbatim
Mapping
mapped · no interpretation or interpolation added by this passport
What the mapping says
Recommendation R-09-008 followed the fatal Newton collision of 28 May 2008, in which a train travelling about 38 mph struck the rear of another and the operator was killed; the board found that 'contributing to the accident was the lack of a positive train control system'. The recommendation was addressed to the Federal Transit Administration.
Caveat
The NTSB recommends; it cannot order. The recommendation went to the FTA, not to the MBTA.

Sources carrying this claim

  1. NTSB — Collision of Two MBTA Green Line Trains, Newton, 28 May 2008 (RAR-09/02)
Claim 4 clm-28632db03e9f0166 quantitative
a 2019 contract collapsed and was re-let to Piper Networks for $112.5M in 2025
Published field
snippet · verbatim
Mapping
mapped · no interpretation or interpolation added by this passport
What the mapping says
The Boston Globe reports an US$83M contract awarded in 2019 to BBR, later acquired by Stadler, on which the MBTA had paid about US$18M before terminating it in June 2024. The February 2025 board summary awards the replacement to Piper Networks, not to exceed US$112,529,564.
Caveat
The Globe article is paywalled and the board document is a PDF the review tooling could not render; both figures were read through the search index of the same documents and are consistent with each other.

Sources carrying this claim

  1. Boston Globe — MBTA scraps Green Line crash prevention contract, will start over (7 June 2024)
  2. MBTA Board of Directors — GLTPS-2 Procurement staff summary, 25 February 2025 (operator)
Claim 5 clm-307be9b08afc2da9 quantitative
Phase 1, the alerts, was due in spring 2026 and is now anticipated in summer 2026
Published field
snippet · verbatim
Mapping
mapped · no interpretation or interpolation added by this passport
What the mapping says
NBC10 Boston in October 2025: 'Phase one of the system will be complete next spring.' The MBTA's own January 2026 update: 'Following a testing and data collection period over the next several months, the MBTA anticipates Phase 1 of GLTPS will be operational in summer 2026.'
Caveat
No claim-specific caveat recorded

Sources carrying this claim

  1. NBC10 Boston — Here’s an exclusive look at the MBTA’s new train protection system on the Green Line (8 October 2025)
  2. MBTA — Essential work across the subway and commuter rail system in 2025 (operator, 16 January 2026)
Claim 6 clm-82ce992ddba7a78e quantitative
Automatic braking is due 2028
Published field
snippet · verbatim
Mapping
mapped · no interpretation or interpolation added by this passport
What the mapping says
CommonWealth Beacon reports that Phase 2 — automatic speed control and braking — is not anticipated on trains until 2028; NBC10 Boston reports the same end date for full operation.
Caveat
No claim-specific caveat recorded

Sources carrying this claim

  1. CommonWealth Beacon — The T will soon roll out Green Line trolleys with anti-collision tech
  2. NBC10 Boston — Here’s an exclusive look at the MBTA’s new train protection system on the Green Line (8 October 2025)
Claim 7 clm-22444730a002d817 quantitative
The NTSB recommends and cannot compel; the FTA, a different agency, is the one that issued binding directives to the MBTA in 2022
Published field
lesson · verbatim
Mapping
mapped · no interpretation or interpolation added by this passport
What the mapping says
Recommendation R-09-008 was addressed to the FTA rather than to the MBTA. The FTA's own page records a separate action: a Safety Management Inspection of the MBTA between 14 April and 30 June 2022, reported on 31 August 2022 with 20 findings and four Special Directives to the MBTA.
Caveat
The FTA's 2022 directives are a separate action and did not create this project.

Sources carrying this claim

  1. NTSB — Collision of Two MBTA Green Line Trains, Newton, 28 May 2008 (RAR-09/02)
  2. Federal Transit Administration — Special Directive 22-12 and the MBTA Safety Management Inspection
Claim 8 clm-6868524aa4eb9d5e descriptive
Seventeen years after the NTSB asked for collision avoidance on the Green Line, no train is protected by it yet
Published field
lesson · verbatim
Mapping
mapped · no interpretation or interpolation added by this passport
What the mapping says
The most recent collision of the type the system is meant to stop happened on 9 February 2025 at East Somerville: a train passed a red signal at about 32 mph and struck a stationary train, injuring six people. On the 2021 Commonwealth Avenue collision the NTSB stated that 'had such a system been in place at the time of the accident, this collision would have been prevented'. The operator's page still describes alerts only.
Caveat
No claim-specific caveat recorded

Sources carrying this claim

  1. NTSB — Collision at East Somerville station, 9 February 2025 (investigation RD25FR007)
  2. WBUR — In final report, feds fault driver, overdue safety features in 2021 Green Line crash (5 January 2023)
  3. MBTA — Green Line Train Protection System (operator project page)

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 2026-08-27-claims-and-sources effective 2026-08-27 · created 2026-08-27

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

Erratum on this revision's envelope. The snapshot, its hash and its permanent link are untouched.

  • createdAt previously read 2026-08-29T12:00:00Z. The batching script that produced this revision advanced createdAt into the future to satisfy the strictly-increasing order the validator requires per entity. The value never recorded a real event; the corrected value is the moment the revision provably existed in the repository. Corrected to 2026-08-27T02:33:50Z on 2026-08-27; evidence: first appears in commit 36d00a0e15, committed 2026-08-27T02:33:50Z.
sha256:891b3e5a20d4f85f13bc2ba01fd47349044795185c61e6ad0c9e1c6e5cf22703
Revision history → Permanent version link → Machine-readable record → Evidence Constitution →
8
of 8 claims mapped
11
source dossiers
8
publication dates recorded
0
archives linked
0
exact locators
0
content captures hashed

Governance facts carried by the record

Operator
Massachusetts Bay Transportation Authority (MBTA)
Actor types
utility
Funding model
public
Funding description
MBTA capital programme
Cost
≈US$112.5M Piper Networks contract (2025), after an US$83M contract awarded in 2019 to BBR/Stadler was abandoned in 2024 with US$18M paid
Ownership
Not recorded
Decision rights
Not recorded
Exit conditions
Not recorded

11 source dossiers

MBTA — Green Line Train Protection System (operator project page) mbta.com · 3 linked claims

Open original source ↗

Stable source ID
src-ea4bd5c1a5b6a988
Publisher
Name not classified · mbta.com
Type / language
web-page · language not classified
Published
Not recorded
Updated
Not recorded
Source last checked
No source-level check date
Record last verified
2026-08-27
Dossier created
2026-08-29
Retrieved copy
No local capture recorded
Archive
No archived copy linked
Content hash
No captured content hash
Locator
Open the recorded source note

Authoritative description of what the system does and does not do: 'The system continuously monitors train speed and location and alerts operators if a train is moving too fast or getting too close to another train.' Phase 1 'adds audible and visual alarms to alert operators about speed violations and avoid collisions'; Phase 2 'adds additional protections to help prevent passing stop signals and support safe operation in temporary slow zones'. The operator never claims the driver is replaced. Also the source for the fitting count: 'So far, 20 trains have been equipped with the new technology.' A living page that carries no date of its own, hence no publication date here.

Descriptive only — not page/paragraph exact
Claims linked
MBTA — Essential work across the subway and commuter rail system in 2025 (operator, 16 January 2026) mbta.com · 1 linked claim

Open original source ↗

Stable source ID
src-fe2124955e629888
Publisher
Name not classified · mbta.com
Type / language
web-page · language not classified
Published
2026-01-16
Updated
Not recorded
Source last checked
No source-level check date
Record last verified
2026-08-27
Dossier created
2026-08-29
Retrieved copy
No local capture recorded
Archive
No archived copy linked
Content hash
No captured content hash
Locator
Open the recorded source note

Sentence-level source for build progress and schedule: 'More than 930 GLTPS anchors installed', 'nearly 68,000 feet of messenger wire installed', 'more than 200,000 feet of cable have been installed within the track area', and 'more than 330 additional anchors along the B, C, and E branches in spring 2026'. Scope covers the signalized branches from North Station to Medford/Tufts and Union Square, the core tunnel from all branch portals to North Station, and the D branch from Riverside to Fenway — which establishes that the Green Line Extension is included. Schedule: 'Following a testing and data collection period over the next several months, the MBTA anticipates Phase 1 of GLTPS will be operational in summer 2026.'

Descriptive only — not page/paragraph exact
Claims linked
MBTA Board of Directors — GLTPS-2 Procurement staff summary, 25 February 2025 (operator) cdn.mbta.com · 2 linked claims

Open original source ↗

Stable source ID
src-50176f4d09eecf48
Publisher
Name not classified · cdn.mbta.com
Type / language
pdf · language not classified
Published
2025-02-25
Updated
Not recorded
Source last checked
No source-level check date
Record last verified
2026-08-27
Dossier created
2026-08-29
Retrieved copy
No local capture recorded
Archive
No archived copy linked
Content hash
No captured content hash
Locator
Open the recorded source note

Contract source: award to Piper Networks not to exceed US$112,529,564; technology described as 'Piper's Cenelec SIL-4 Ultra-Wideband positioning technology to localize trains operating both at grade and in the underground central subway areas'; three deliverables — collision avoidance, overspeed protection, and full territory response to signals and speed changes. PDF; could not be rendered by the review tooling, figures verified through the search index of the same document and corroborated by the Boston Globe and CommonWealth Beacon reports listed below. Note that a SIL-4 rating is a design certification, not a result.

Descriptive only — not page/paragraph exact
Claims linked
NTSB — Collision of Two MBTA Green Line Trains, Newton, 28 May 2008 (RAR-09/02) ntsb.gov · 3 linked claims

Open original source ↗

Stable source ID
src-d517875621c3c93e
Publisher
Name not classified · ntsb.gov
Type / language
pdf · language not classified
Published
2008-05-28
Updated
Not recorded
Source last checked
No source-level check date
Record last verified
2026-08-27
Dossier created
2026-08-29
Retrieved copy
No local capture recorded
Archive
No archived copy linked
Content hash
No captured content hash
Locator
Open the recorded source note

The fatal accident behind the recommendation: a westbound train travelling about 38 mph struck the rear of another near Waban, killing operator Ter'rese Edmonds. Probable cause was the operator's failure to comply with the controlling signal indication, consistent with an episode of micro-sleep; 'contributing to the accident was the lack of a positive train control system that would have intervened to stop the train and prevent the collision.' Source for the precise defect: Green Line trains 'do not incorporate systems such as trip stops (mechanical arms or electrical inductors that slow or stop a train if the operator fails to respond)'. Recommendation R-09-008 was addressed to the Federal Transit Administration, not to the MBTA — the NTSB recommends, it does not order.

Descriptive only — not page/paragraph exact
Claims linked
WBUR — In final report, feds fault driver, overdue safety features in 2021 Green Line crash (5 January 2023) wbur.org · 1 linked claim

Open original source ↗

Stable source ID
src-4d46ce4f1e748195
Publisher
Name not classified · wbur.org
Type / language
web-page · language not classified
Published
2023-01-05
Updated
Not recorded
Source last checked
No source-level check date
Record last verified
2026-08-27
Dossier created
2026-08-29
Retrieved copy
No local capture recorded
Archive
No archived copy linked
Content hash
No captured content hash
Locator
Open the recorded source note

Carries the NTSB's finding on the 30 July 2021 Commonwealth Avenue collision in the Board's own words: 'Had such a system been in place at the time of the accident, this collision would have been prevented.' Probable cause was the operator's sudden acceleration and 'loss of situational awareness'; 24 passengers and three MBTA workers were taken to hospital. Also records the MBTA target current at that date — completion by June 2025, itself a two-year slip.

Descriptive only — not page/paragraph exact
Claims linked
NTSB — Collision at East Somerville station, 9 February 2025 (investigation RD25FR007) ntsb.gov · 1 linked claim

Open original source ↗

Stable source ID
src-7477ca779cc560e1
Publisher
Name not classified · ntsb.gov
Type / language
web-page · language not classified
Published
2025-02-09
Updated
Not recorded
Source last checked
No source-level check date
Record last verified
2026-08-27
Dossier created
2026-08-29
Retrieved copy
No local capture recorded
Archive
No archived copy linked
Content hash
No captured content hash
Locator
Open the recorded source note

The most recent accident of exactly the type the system is meant to stop, on the newest section of line: at about 12:22 a.m. a train travelling about 32 mph entered a 25 mph zone, passed a red signal and entered the 10 mph station zone before striking a stationary out-of-service train. Six people were injured and the MBTA estimated US$6.6 million in damage. Preliminary report published 6 March 2025. It happened seventeen days before the board approved the Piper contract.

Descriptive only — not page/paragraph exact
Claims linked
Boston Globe — MBTA scraps Green Line crash prevention contract, will start over (7 June 2024) bostonglobe.com · 1 linked claim

Open original source ↗

Stable source ID
src-efee7255e5b08ab7
Publisher
Name not classified · bostonglobe.com
Type / language
web-page · language not classified
Published
2024-06-07
Updated
Not recorded
Source last checked
No source-level check date
Record last verified
2026-08-27
Dossier created
2026-08-29
Retrieved copy
No local capture recorded
Archive
No archived copy linked
Content hash
No captured content hash
Locator
Open the recorded source note

Source for the abandoned first attempt: an US$83M contract awarded in 2019 to the German firm BBR, later acquired by Stadler, on which the MBTA had paid about US$18M without seeing meaningful progress; the agency terminated it in June 2024 and moved to recoup the money. Paywalled; the figures were verified through the search index of the same article and are consistent with the February 2025 board procurement.

Descriptive only — not page/paragraph exact
Claims linked
CommonWealth Beacon — The T will soon roll out Green Line trolleys with anti-collision tech commonwealthbeacon.org · 1 linked claim

Open original source ↗

Stable source ID
src-f5be84309de633c9
Publisher
Name not classified · commonwealthbeacon.org
Type / language
web-page · language not classified
Published
2025-12-03
Updated
2025-12-05
Source last checked
No source-level check date
Record last verified
2026-08-27
Dossier created
2026-08-29
Retrieved copy
No local capture recorded
Archive
No archived copy linked
Content hash
No captured content hash
Locator
Open the recorded source note

Independent reporting that keeps the two phases apart: Phase 1 gives 'audible and visual alerts if the system detects a collision risk', Phase 2 adds automatic speed control and braking and is not anticipated on trains until 2028. Also the source for the slip — officials first said Phase 1 would be complete by December 2025 and then moved it to mid-2026, against a contract deadline with Piper of March 2027.

Descriptive only — not page/paragraph exact
Claims linked
Federal Transit Administration — Special Directive 22-12 and the MBTA Safety Management Inspection transit.dot.gov · 1 linked claim

Open original source ↗

Stable source ID
src-79e41a0412cafd14
Publisher
Name not classified · transit.dot.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
2026-08-27
Dossier created
2026-08-29
Retrieved copy
No local capture recorded
Archive
No archived copy linked
Content hash
No captured content hash
Locator
Open the recorded source note

Included so the two federal bodies are not conflated. The FTA — which can compel, unlike the NTSB — conducted its Safety Management Inspection of the MBTA between 14 April and 30 June 2022 and released the report on 31 August 2022 with 20 findings, accompanied by four Special Directives to the MBTA and one to the Massachusetts Department of Public Utilities. That is a separate action from the NTSB's 2009 recommendation and did not create this project.

Descriptive only — not page/paragraph exact
Claims linked
MBTA — Track Improvement Program (operator) mbta.com · background

Open original source ↗

Stable source ID
src-7dd56ec72e8e3144
Publisher
Name not classified · mbta.com
Type / language
web-page · language not classified
Published
Not recorded
Updated
Not recorded
Source last checked
No source-level check date
Record last verified
2026-08-27
Dossier created
2026-08-29
Retrieved copy
No local capture recorded
Archive
No archived copy linked
Content hash
No captured content hash
Locator
Open the recorded source note

Context for the wider safety crisis this project sits inside, kept to one dated figure: the programme removed more than 220 speed restrictions and replaced more than 250,000 feet of rail, clearing the last track-related slow zones in December 2024 after 23 planned closures across four lines during that year. Operator-reported; used for scale only, not as an impact figure for the train protection system.

Descriptive only — not page/paragraph exact
Claims linked
Background source; no baseline claim points here
NBC10 Boston — Here’s an exclusive look at the MBTA’s new train protection system on the Green Line (8 October 2025) nbcboston.com · 3 linked claims

Open original source ↗

Stable source ID
src-1a7fc0bab3b6c3a0
Publisher
Name not classified · nbcboston.com
Type / language
web-page · language not classified
Published
2025-10-08
Updated
Not recorded
Source last checked
No source-level check date
Record last verified
2026-08-27
Dossier created
2026-08-29
Retrieved copy
No local capture recorded
Archive
No archived copy linked
Content hash
No captured content hash
Locator
Open the recorded source note

Ride-along with the MBTA's chief operating officer, Ryan Coholan. Describes the on-board hardware — sensors on the front, back and roof of each train talking to trackside anchors, and a cab display — and states the intended end behaviour in plain words: 'If the operator doesn't take any action the system will apply the brakes and stop the train itself.' Also the schedule as it stood in October 2025: 'Phase one of the system will be complete next spring and the entire GLTPS will be fully operational by 2028' — the spring 2026 date the MBTA's own January 2026 update then moved to summer 2026.

Descriptive only — not page/paragraph exact
Claims linked
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.