1001 Smart Cities

Permanent project revision

Green Line Train Protection System

Revision 2026-08-27-correction-run · effective 2026-08-27

Superseded. A later revision exists: 2026-08-27-correction-run-2 →

unreviewed

Re-read the board paper and the operator page in full. Removed an invented 'Cenelec SIL-4' attribution, added the contractual Phase 1 date of March 2027 and the total project budget, replaced two dead sources and dated the rest.

sha256:9e703f7597fb97b98f078fd6e0e00965a93f693c9bca6a3a1f02b713b0b2bf95
All revisions → Current entity page →

Change set

  • replace /snapshot/projectFingerprint — Updated projectFingerprint to the current sourced project record.
  • replace /snapshot/governance — Updated governance to the current sourced project record.
  • replace /snapshot/claims — Updated claims to the current sourced project record.
  • replace /snapshot/sources — Updated sources to the current sourced project record.
9
of 9 claims mapped
10
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 2009 NTSB report on the Newton collision records that the Green Line had no train protection to stop a train that passed its controlling signal; the operator's current project page describes the system being installed as still being introduced.
Caveat
No claim-specific caveat recorded

Sources carrying this claim

  1. NTSB — RAR-09/02, adopted 14 July 2009: Collision of Two MBTA Green Line Trains, Newton (accident 28 May 2008)
  2. MBTA — Green Line Train Protection System (operator project page)
Claim 2 clm-a00c972645a0e9d6 quantitative
The MBTA is fitting a Piper Networks overlay that uses GPS-RTK above ground and ultra-wideband positioning in the tunnels to warn 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 board paper says 'Piper will deploy GPS-RTK for speed and collision warnings' above ground and 'UWB (Ultra Wide Band)' underground, in 'a stand-alone, non-vital overlay system'; the project page states 'So far, 20 trains have been equipped with the new technology.'
Caveat
No claim-specific caveat recorded

Sources carrying this claim

  1. MBTA Board of Directors — GLTPS-2 Procurement staff summary, 25 February 2025 (operator)
  2. MBTA — Green Line Train Protection System (operator project page)
  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
The NTSB's 2009 report on the 2008 Newton collision made the recommendation; CommonWealth Beacon dates it to 2009 as well.
Caveat
No claim-specific caveat recorded

Sources carrying this claim

  1. NTSB — RAR-09/02, adopted 14 July 2009: Collision of Two MBTA Green Line Trains, Newton (accident 28 May 2008)
  2. CommonWealth Beacon — The T will soon roll out Green Line trolleys with anti-collision tech
Claim 4 clm-d311f6f7e58f4673 quantitative
a 2019 contract with the German firm BBR was scrapped in 2024 and re-let to Piper Networks in February 2025 for $112,529,564, inside a total project budget of $219,103,608
Published field
snippet · verbatim
Mapping
mapped · no interpretation or interpolation added by this passport
What the mapping says
'The T contracted with German firm BBR in 2019; five years later… the agency scrapped the deal and reset the project'; the February 2025 board paper sets the negotiated price at $112,529,564 and the total project budget at $219,103,608.
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. MBTA Board of Directors — GLTPS-2 Procurement staff summary, 25 February 2025 (operator)
Claim 5 clm-b6a921eac55cf130 quantitative
The board paper gave Phase 1, the alerts, a December 2025 completion date; the general manager's November 2025 report moved it to mid-2026, and the MBTA notes the contract itself only requires Phase 1 by March 2027
Published field
snippet · verbatim
Mapping
mapped · no interpretation or interpolation added by this passport
What the mapping says
The board paper's phase table reads 'Phase 1 … Complete: December 2025'; CommonWealth Beacon reports the 20 November 2025 GM presentation sliding it to mid-2026 and the MBTA's answer that 'the contract with equipment manufacturer Piper calls for the first phase to be done by March 2027'.
Caveat
No claim-specific caveat recorded

Sources carrying this claim

  1. MBTA Board of Directors — GLTPS-2 Procurement staff summary, 25 February 2025 (operator)
  2. CommonWealth Beacon — The T will soon roll out Green Line trolleys with anti-collision tech
Claim 6 clm-e63a778335d3e1f8 quantitative
Phase 2, which slows or stops a train that ignores the warnings, is contracted to complete in June 2028
Published field
snippet · verbatim
Mapping
mapped · no interpretation or interpolation added by this passport
What the mapping says
The board paper describes Phase 2 as an avoidance system that 'Automatically slows or stops trains if warnings ignored' with 'Complete: June 2028'; CommonWealth Beacon reports Phase 2 is not anticipated on trains until 2028.
Caveat
No claim-specific caveat recorded

Sources carrying this claim

  1. MBTA Board of Directors — GLTPS-2 Procurement staff summary, 25 February 2025 (operator)
  2. CommonWealth Beacon — The T will soon roll out Green Line trolleys with anti-collision tech
Claim 7 clm-8a9fb94a4791298a quantitative
The NTSB recommends and cannot compel; separate federal attention from the Federal Transit Administration in 2022 is what produced corrective action orders
Published field
lesson · verbatim
Mapping
mapped · no interpretation or interpolation added by this passport
What the mapping says
The NTSB issues safety recommendations; WBUR reports that the MBTA's problems 'drew separate federal attention this year with a blistering Federal Transit Administration investigation that prompted multiple corrective action orders'.
Caveat
No claim-specific caveat recorded

Sources carrying this claim

  1. NTSB — RAR-09/02, adopted 14 July 2009: Collision of Two MBTA Green Line Trains, Newton (accident 28 May 2008)
  2. WBUR — In final report, feds fault driver, overdue safety features in 2021 Green Line crash (5 January 2023)
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 February 2025 East Somerville collision is the same failure mode on the newest section of line — 'passed a red (stop) signal'; the NTSB found of the 2021 collision that 'Had such a system been in place at the time of the accident, this collision would have been prevented'; the operator page still describes the alerts as being introduced.
Caveat
No claim-specific caveat recorded

Sources carrying this claim

  1. WBUR / State House News Service — NTSB: Green Line trolley went through stop sign before crash (6 March 2025)
  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)
Claim 9 clm-64c2797860fa4623 descriptive
the deadlines that slipped were the general manager's ambition, while the contractual one is two years later and has not moved
Published field
lesson · verbatim
Mapping
mapped · no interpretation or interpolation added by this passport
What the mapping says
The MBTA's own answer to the slip: the contract requires Phase 1 by March 2027 and 'the earlier dates mentioned publicly instead represented Eng's preference'.
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

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-correction-run effective 2026-08-27 · created 2026-08-27

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

sha256:9e703f7597fb97b98f078fd6e0e00965a93f693c9bca6a3a1f02b713b0b2bf95
Revision history → Permanent version link → Machine-readable record → Evidence Constitution →
9
of 9 claims mapped
10
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$112,529,564 Piper Networks contract approved February 2025, inside a total project budget of US$219,103,608; a 2019 contract with the German firm BBR was scrapped in 2024
Ownership
Not recorded
Decision rights
Not recorded
Exit conditions
Not recorded

10 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
2026-08-27
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 · background

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
2026-08-27
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
Background source; no baseline claim points here
MBTA Board of Directors — GLTPS-2 Procurement staff summary, 25 February 2025 (operator) cdn.mbta.com · 4 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
2026-08-27
Retrieved copy
No local capture recorded
Archive
No archived copy linked
Content hash
No captured content hash
Locator
Open the recorded source note

Board paper of 25 February 2025, read in full (text extracted from the PDF). Scope: 'a stand-alone, non-vital overlay system' with three functions — stopping vehicles before a red signal, speed enforcement, and preventing train-to-train collisions. Technology: 'Piper will deploy GPS-RTK for speed and collision warnings' above ground and 'UWB (Ultra Wide Band)' underground; equipment is LiDAR, a Master Control Unit and a train positioning antenna. Phase 1 'Complete: December 2025', Phase 2 'Complete: June 2028'. 'Negotiated Price: $112,529,564' and 'a total delivered amount not to exceed $112,529,564'; total project budget $219,103,608. One bid was received, from Piper Networks.

Descriptive only — not page/paragraph exact
Claims linked
NTSB — RAR-09/02, adopted 14 July 2009: Collision of Two MBTA Green Line Trains, Newton (accident 28 May 2008) 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
2009-07-14
Updated
Not recorded
Source last checked
No source-level check date
Record last verified
2026-08-27
Dossier created
2026-08-27
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, read in full 2026-08-27 (text extracted from the PDF). 'Adopted July 14, 2009'; the accident itself was 28 May 2008. A westbound train 'traveling about 38 mph, struck the rear of' a stopped train; the striking operator was killed and total damage was about $8.6 million.

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 · 2 linked claims

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
2026-08-27
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.' Read in full 2026-08-27; it is also the source for the separation of the two federal roles — 'The MBTA's glaring safety problems drew separate federal attention this year with a blistering Federal Transit Administration investigation that prompted multiple corrective action orders', against recommendations the NTSB made 'more than a decade ago'.

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 · background

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
2026-08-27
Retrieved copy
No local capture recorded
Archive
No archived copy linked
Content hash
No captured content hash
Locator
Open the recorded source note

Paywalled and not archived; not read here. It is the report CommonWealth Beacon links to for the scrapping of the BBR contract, and is listed for that provenance only. No claim on this entry rests on it, and no figure is taken from it.

Descriptive only — not page/paragraph exact
Claims linked
Background source; no baseline claim points here
CommonWealth Beacon — The T will soon roll out Green Line trolleys with anti-collision tech commonwealthbeacon.org · 5 linked claims

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
2026-08-27
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, read in full. Keeps the phases apart and carries the contractual dates the operator's own announcements do not: 'The T contracted with German firm BBR in 2019; five years later, after Eng took the helm as general manager, the agency scrapped the deal and reset the project'; 'In February, the MBTA's board of directors approved a new $112 million contract with Piper'; 'the contract with equipment manufacturer Piper calls for the first phase to be done by March 2027, and… the earlier dates mentioned publicly instead represented Eng's preference'; and the 20 November 2025 GM report sliding Phase 1 to mid-2026.

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
2026-08-27
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, read 2026-08-27. A rolling programme page that carries no publication date of its own, only dated updates — the completion of the programme is announced there on 23 December 2024. Hence date: null.

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 · 1 linked claim

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
2026-08-27
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
WBUR / State House News Service — NTSB: Green Line trolley went through stop sign before crash (6 March 2025) wbur.org · 1 linked claim

Open original source ↗

Stable source ID
src-9591ba7eaa0694c1
Publisher
Name not classified · wbur.org
Type / language
web-page · language not classified
Published
2025-03-06
Updated
Not recorded
Source last checked
No source-level check date
Record last verified
2026-08-27
Dossier created
2026-08-27
Retrieved copy
No local capture recorded
Archive
No archived copy linked
Content hash
No captured content hash
Locator
Open the recorded source note

Read in full 2026-08-27; by Colin A. Young, State House News Service. Replaces the NTSB's own investigation page for the East Somerville collision, which now answers 'Page not found'. Quotes the preliminary report directly: 'A preliminary review of event recorder and signal data indicates the striking train was traveling about 32 mph when it entered a 25-mph zone, passed a red (stop) signal and entered the 10-mph zone in the station where it collided with the stationary out-of-service train.' Two passengers and four crew were hurt; the MBTA put damage at about $6.6 million.

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.