1001 Smart Cities
🇺🇸 Los Angeles

ATSAC Citywide Adaptive Traffic Signals

🤖 AI-generated summary · ◆ 12 sourced claims · 🔎 Last verified

This overview was generated with AI from the public sources listed below and checked against them before publication. It has not had a complete human fact-check — treat it as a starting point and follow the sources.

12 sourced claims on this page, none individually verified yet — turn on “Sources in the text” to see each one.

How this atlas is made · What “last verified” means · What “source-checked” means · The full record behind this page

Built in-house for the 1984 Olympics with 118 signals, it took until February 2013 to synchronise them all. State auditors later confirmed 4 to 9 percent shorter travel times on two corridors.

Outcome🎯 Succeeded
Evidence📊 Independent
what does this mean?The strongest source is an independent non-academic evaluation: an audit office, a government or EU review, or an NGO. It grades who did the looking — not how well the project went. All four grades →
Run byLos Angeles Department of Transportation (LADOT)
Scale🏙️ City-wide

Part of 1001 Smart Cities — 1,216 documented projects · 🏙️ 12 more in Los Angeles · 🚦 Traffic management guide · 🚲 Mobility projects

LADOT's in-house traffic-signal system, first deployed for the 1984 Olympics with 118 signals, by 2024 connected more than 4,900 signals through 26,000+ sensors and more than 590 cameras. Los Angeles finished synchronising every signal citywide in February 2013; LADOT called it the largest US city with remote control of every signal. In 2022 the control centre moved to a larger site and was expanded ahead of the 2028 Olympics.

Live 📅 since 1984 🤖 Uses AI

📊 Impact

When synchronisation was completed in 2013, LADOT reported average citywide speeds up from 15 to 17.3 mph and intersection delays down 12 percent — the department's own figures. A May 2020 state audit of two state-funded adaptive-control projects found the city had achieved the expected benefits: its floating-car studies showed a 4 to 9 percent reduction in travel time. For one project the original study could not be found and was redone in November 2019.

🎓 Lesson

Even a citywide synchronised network buys modest gains — 'a smoother kind of slow', with more people travelling as speeds improve — and the gain only counts if the measurement is kept: state auditors could confirm one project's benefits only after the city repeated a lost floating-car study.

🚲 MobilityTraffic managementArtificial intelligenceSensors & IoT

Sources

↗ LADOT — ATSAC (authority)Updated November 2024LADOT's programme page: real-time detector loops, cameras at major intersections, signal timing changed as traffic changes; its key-figures sheet (revised November 2024) lists 4,900+ signals, 26,000+ sensors and 590+ CCTV cameras, and estimates a 32% cut in travel delays against a system without automated control.
↗ Patch — Final L.A. Traffic Signals Synchronized (press)Published 21 February 2013Reports that the last of Los Angeles' nearly 4,400 traffic signals were synchronised, completing a $410 million effort; LADOT's design aim was 12% faster travel speed and 16% less time in traffic.
↗ Spectrum News 1 — LA upgrades traffic control for 2028 Olympics (press)Published 30 November 2022Ribbon-cutting for the new ATSAC centre ahead of the 2028 Games: the system controlled 118 signals in 1984 and now manages 4,850; renamed Advanced Transportation System and Coordination.
↗ California Department of Finance — audit of two Proposition 1B signal projects, City of Los Angeles (May 2020)Published 18 May 2020Performance audit requested by Caltrans of two adaptive-control projects funded with $18 million of Proposition 1B money: expected benefits achieved, floating-car studies showed a 4 to 9 percent reduction in travel time; for one project the City could not provide the original study and conducted a new one in November 2019.
↗ Governing — L.A. traffic system completed (press)Published 25 March 2013Reports completion of the network; according to LADOT, Los Angeles is the largest city in the country with complete remote control over every one of its traffic lights.
Show 2 more sourcesShow fewer
↗ Route Fifty — L.A. synchronizes traffic signals, but drivers might not notice (press)Published 4 April 2013Citing LADOT via the Los Angeles Times: average citywide speed up from 15 to 17.3 mph and intersection delays down 12 percent, a 'smoother kind of slow'; a USC engineer notes that faster traffic leads more people to travel.
↗ LADOT — ATSAC fact sheet (authority)LADOT fact sheet: over 4,900 signalised intersections, over 26,000 vehicle detectors and over 590 CCTV cameras; describes the system as adaptive; its benefits section cites a 2013 Texas A&M study of signal synchronisation in general, not of ATSAC.

📅 How old is the evidence?

Two clocks, kept apart: when this entry’s sources were published, and what has happened to its record in the atlas. Documented span: since 1984. 5 of 7 sources carry a publication date, from 21 February 2013 to 30 November 2022.

When the sources were published

  1. Patch · pressPatch — Final L.A. Traffic Signals Synchronized (press)
  2. Governing · pressGoverning — L.A. traffic system completed (press)
  3. Route Fifty · pressRoute Fifty — L.A. synchronizes traffic signals, but drivers might not notice (press)
  4. California Department of Finance, Office of State Audits and Evaluations · oversight bodyCalifornia Department of Finance — audit of two Proposition 1B signal projects, City of Los Angeles (May 2020)
  5. Spectrum News 1 · pressSpectrum News 1 — LA upgrades traffic control for 2028 Olympics (press)

Every source, with links ↑

What happened to this record

  1. Entered the record
  2. Sources last read

Every revision, permanent →

Show your work What this page rests on and what it can’t tell you · all 12 claims with their sources · the forensic record

Evidence file · public beta 12 addressable claims, 7 source dossiers, one permanent baseline. The file is unreviewed — an AI-assisted structural migration, not a human or expert endorsement. Every revision keeps a permanent copy under revision history.

Inspect the claims, one by one — verbatim text, sources and caveats for all 12

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-94422b217c316714 descriptive
LADOT's in-house traffic-signal system
Published field
snippet · verbatim
Mapping
mapped · no interpretation or interpolation added by this file
What the mapping says
LADOT says its staff invented the technology; Governing reports the computer systems were developed in-house and maintained internally.
Caveat
No claim-specific caveat recorded

Sources carrying this claim

  1. LADOT — ATSAC (authority)
  2. Governing — L.A. traffic system completed (press)
Claim 2 clm-6578bd94675ad21d quantitative
first deployed for the 1984 Olympics with 118 signals
Published field
snippet · verbatim
Mapping
mapped · no interpretation or interpolation added by this file
What the mapping says
Spectrum News: in 1984 the system was able to control 118 traffic signals.
Caveat
No claim-specific caveat recorded

Sources carrying this claim

  1. Spectrum News 1 — LA upgrades traffic control for 2028 Olympics (press)
Claim 3 clm-a0319d6f84f73095 quantitative
by 2024 connected more than 4,900 signals through 26,000+ sensors and more than 590 cameras
Published field
snippet · verbatim
Mapping
mapped · no interpretation or interpolation added by this file
What the mapping says
LADOT's key-figures sheet (revised November 2024) and fact sheet list 4,900+ signals, 26,000+ sensors/detectors and 590+ CCTV cameras.
Caveat
The figures are printed in an image on the programme page; the fact-sheet text is the readable form.

Sources carrying this claim

  1. LADOT — ATSAC (authority)
  2. LADOT — ATSAC fact sheet (authority)
Claim 4 clm-3a5172d32ba41337 quantitative
Los Angeles finished synchronising every signal citywide in February 2013
Published field
snippet · verbatim
Mapping
mapped · no interpretation or interpolation added by this file
What the mapping says
Patch (21 February 2013): the last of the nearly 4,400 signals were synchronised on Tuesday.
Caveat
No claim-specific caveat recorded

Sources carrying this claim

  1. Patch — Final L.A. Traffic Signals Synchronized (press)
Claim 5 clm-23d78e243f21b3b8 descriptive
LADOT called it the largest US city with remote control of every signal
Published field
snippet · verbatim
Mapping
mapped · no interpretation or interpolation added by this file
What the mapping says
Governing attributes to LADOT that Los Angeles is the largest city in the country with complete remote control over every traffic light.
Caveat
A claim by the operator, not an independent comparison.

Sources carrying this claim

  1. Governing — L.A. traffic system completed (press)
Claim 6 clm-17996373c1a0f1b5 quantitative
In 2022 the control centre moved to a larger site and was expanded ahead of the 2028 Olympics
Published field
snippet · verbatim
Mapping
mapped · no interpretation or interpolation added by this file
What the mapping says
Spectrum News: the new ATSAC headquarters opened on an upper floor of the Caltrans building, a larger space reflecting an expansion of the system, with LA28 present.
Caveat
No claim-specific caveat recorded

Sources carrying this claim

  1. Spectrum News 1 — LA upgrades traffic control for 2028 Olympics (press)
Claim 7 clm-cf2d20989c432f6d quantitative
LADOT reported average citywide speeds up from 15 to 17.3 mph and intersection delays down 12 percent
Published field
impact · verbatim
Mapping
mapped · no interpretation or interpolation added by this file
What the mapping says
Route Fifty, citing the city transportation department via the Los Angeles Times: speed from 15 to 17.3 mph citywide, intersection delays down 12 percent.
Caveat
No method or baseline period is given for these figures.

Sources carrying this claim

  1. Route Fifty — L.A. synchronizes traffic signals, but drivers might not notice (press)
Claim 8 clm-cf947ff7c72d76dc quantitative
A May 2020 state audit of two state-funded adaptive-control projects found the city had achieved the expected benefits
Published field
impact · verbatim
Mapping
mapped · no interpretation or interpolation added by this file
What the mapping says
The Department of Finance's Office of State Audits and Evaluations concluded the City achieved the expected project benefits/outcomes for both projects.
Caveat
No claim-specific caveat recorded

Sources carrying this claim

  1. California Department of Finance — audit of two Proposition 1B signal projects, City of Los Angeles (May 2020)
Claim 9 clm-5225a6af9f970a49 quantitative
its floating-car studies showed a 4 to 9 percent reduction in travel time
Published field
impact · verbatim
Mapping
mapped · no interpretation or interpolation added by this file
What the mapping says
The audit tables quote the Final Delivery Reports: the floating car study showed a 4 to 9 percent reduction in travel time.
Caveat
The studies were the city's own; the auditors checked that they supported the reported benefits.

Sources carrying this claim

  1. California Department of Finance — audit of two Proposition 1B signal projects, City of Los Angeles (May 2020)
Claim 10 clm-32f539f8c9e8ac6d quantitative
For one project the original study could not be found and was redone in November 2019
Published field
impact · verbatim
Mapping
mapped · no interpretation or interpolation added by this file
What the mapping says
Finding 1: the City could not provide the floating car study cited in the report and conducted an additional study in November 2019.
Caveat
No claim-specific caveat recorded

Sources carrying this claim

  1. California Department of Finance — audit of two Proposition 1B signal projects, City of Los Angeles (May 2020)
Claim 11 clm-058d65273a8bdb51 descriptive
Even a citywide synchronised network buys modest gains — 'a smoother kind of slow', with more people travelling as speeds improve
Published field
lesson · verbatim
Mapping
mapped · no interpretation or interpolation added by this file
What the mapping says
Route Fifty quotes the Los Angeles Times' 'smoother kind of slow' and a USC engineer: improved traffic speed leads to more people traveling.
Caveat
No claim-specific caveat recorded

Sources carrying this claim

  1. Route Fifty — L.A. synchronizes traffic signals, but drivers might not notice (press)
Claim 12 clm-42ea200e44096b00 descriptive
state auditors could confirm one project's benefits only after the city repeated a lost floating-car study
Published field
lesson · verbatim
Mapping
mapped · no interpretation or interpolation added by this file
What the mapping says
The audit found the original study missing and accepted the benefits on the strength of the November 2019 repeat study.
Caveat
No claim-specific caveat recorded

Sources carrying this claim

  1. California Department of Finance — audit of two Proposition 1B signal projects, City of Los Angeles (May 2020)
Forensic record — source dossiers, gaps, hashes and the exact revision this page renders

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 2026-10-14-baseline effective 2026-10-14 · created 2026-10-14

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

sha256:582d32586787654f81029d400ec13148a489fbbb0c7c9c9b3b548e5b4a31afe2
Revision history → Permanent version link → Machine-readable record → Evidence Constitution →
12
of 12 claims mapped
7
source dossiers
5
publication dates recorded
0
archives linked
0
exact locators
0
content captures hashed

Governance facts carried by the record

Operator
Los Angeles Department of Transportation (LADOT)
Actor types
city-government
Funding model
public
Funding description
Not recorded
Cost
Not recorded
Ownership
Not recorded
Decision rights
Not recorded
Exit conditions
Not recorded

7 source dossiers

LADOT — ATSAC (authority) ladot.lacity.gov · 2 linked claims

Open original source ↗

Stable source ID
src-451adf25987df274
Publisher
Name not classified · ladot.lacity.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
2026-10-14
Dossier created
2026-10-14
Retrieved copy
No local capture recorded
Archive
No archived copy linked
Content hash
No captured content hash
Locator
Open the recorded source note

LADOT's programme page: real-time detector loops, cameras at major intersections, signal timing changed as traffic changes; its key-figures sheet (revised November 2024) lists 4,900+ signals, 26,000+ sensors and 590+ CCTV cameras, and estimates a 32% cut in travel delays against a system without automated control.

Descriptive only — not page/paragraph exact
Claims linked
Patch — Final L.A. Traffic Signals Synchronized (press) patch.com · 1 linked claim

Open original source ↗

Stable source ID
src-efd1c8147c051a10
Publisher
Name not classified · patch.com
Type / language
web-page · language not classified
Published
2013-02-21
Updated
Not recorded
Source last checked
No source-level check date
Record last verified
2026-10-14
Dossier created
2026-10-14
Retrieved copy
No local capture recorded
Archive
No archived copy linked
Content hash
No captured content hash
Locator
Open the recorded source note

Reports that the last of Los Angeles' nearly 4,400 traffic signals were synchronised, completing a $410 million effort; LADOT's design aim was 12% faster travel speed and 16% less time in traffic.

Descriptive only — not page/paragraph exact
Claims linked
Spectrum News 1 — LA upgrades traffic control for 2028 Olympics (press) spectrumnews1.com · 2 linked claims

Open original source ↗

Stable source ID
src-bde2a4debb480aa8
Publisher
Name not classified · spectrumnews1.com
Type / language
web-page · language not classified
Published
2022-11-30
Updated
Not recorded
Source last checked
No source-level check date
Record last verified
2026-10-14
Dossier created
2026-10-14
Retrieved copy
No local capture recorded
Archive
No archived copy linked
Content hash
No captured content hash
Locator
Open the recorded source note

Ribbon-cutting for the new ATSAC centre ahead of the 2028 Games: the system controlled 118 signals in 1984 and now manages 4,850; renamed Advanced Transportation System and Coordination.

Descriptive only — not page/paragraph exact
Claims linked
California Department of Finance — audit of two Proposition 1B signal projects, City of Los Angeles (May 2020) ig.dot.ca.gov · 4 linked claims

Open original source ↗

Stable source ID
src-a84ca672c832a702
Publisher
Name not classified · ig.dot.ca.gov
Type / language
pdf · language not classified
Published
2020-05-18
Updated
Not recorded
Source last checked
No source-level check date
Record last verified
2026-10-14
Dossier created
2026-10-14
Retrieved copy
No local capture recorded
Archive
No archived copy linked
Content hash
No captured content hash
Locator
Open the recorded source note

Performance audit requested by Caltrans of two adaptive-control projects funded with $18 million of Proposition 1B money: expected benefits achieved, floating-car studies showed a 4 to 9 percent reduction in travel time; for one project the City could not provide the original study and conducted a new one in November 2019.

Descriptive only — not page/paragraph exact
Claims linked
Governing — L.A. traffic system completed (press) governing.com · 2 linked claims

Open original source ↗

Stable source ID
src-3650726666efd9f3
Publisher
Name not classified · governing.com
Type / language
web-page · language not classified
Published
2013-03-25
Updated
Not recorded
Source last checked
No source-level check date
Record last verified
2026-10-14
Dossier created
2026-10-14
Retrieved copy
No local capture recorded
Archive
No archived copy linked
Content hash
No captured content hash
Locator
Open the recorded source note

Reports completion of the network; according to LADOT, Los Angeles is the largest city in the country with complete remote control over every one of its traffic lights.

Descriptive only — not page/paragraph exact
Claims linked
Route Fifty — L.A. synchronizes traffic signals, but drivers might not notice (press) route-fifty.com · 2 linked claims

Open original source ↗

Stable source ID
src-e1e112322238c37a
Publisher
Name not classified · route-fifty.com
Type / language
web-page · language not classified
Published
2013-04-04
Updated
Not recorded
Source last checked
No source-level check date
Record last verified
2026-10-14
Dossier created
2026-10-14
Retrieved copy
No local capture recorded
Archive
No archived copy linked
Content hash
No captured content hash
Locator
Open the recorded source note

Citing LADOT via the Los Angeles Times: average citywide speed up from 15 to 17.3 mph and intersection delays down 12 percent, a 'smoother kind of slow'; a USC engineer notes that faster traffic leads more people to travel.

Descriptive only — not page/paragraph exact
Claims linked
LADOT — ATSAC fact sheet (authority) ladot.lacity.gov · 1 linked claim

Open original source ↗

Stable source ID
src-f4ef96fea2db4baa
Publisher
Name not classified · ladot.lacity.gov
Type / language
pdf · language not classified
Published
Not recorded
Updated
Not recorded
Source last checked
No source-level check date
Record last verified
2026-10-14
Dossier created
2026-10-14
Retrieved copy
No local capture recorded
Archive
No archived copy linked
Content hash
No captured content hash
Locator
Open the recorded source note

LADOT fact sheet: over 4,900 signalised intersections, over 26,000 vehicle detectors and over 590 CCTV cameras; describes the system as adaptive; its benefits section cites a 2013 Texas A&M study of signal synchronisation in general, not of ATSAC.

Descriptive only — not page/paragraph exact
Claims linked
Known limits of this file
  • 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.

Continue exploring

Compare this project

🇺🇸 Surtrac AI Traffic Signals · Pittsburgh Adaptive signals, central vs local: LA retimes 4,900+ signals from one system (1984-); Surtrac lets each junction decide for itself (2012). 🇹🇭 BMA AI Adaptive Traffic Signals · Bangkok Cameras and signals: LA's ATSAC links 590+ cameras and 4,900+ signals (2024); Bangkok tuned 74 junctions from CCTV in 2024. 🇨🇳 Beijing TOCC Traffic Coordination Center · Beijing Citywide traffic control rooms: LA's ATSAC links 4,900+ signals (1984-); Beijing's TOCC coordinates modes from 93k vehicle GPS (2011).

Explore the wider context

🚦 Asphalt or algorithms📖 Green wave📖 Adaptive traffic signals📖 Automated speed enforcement (speed cameras)
📎 Cite this project

1001 Smart Cities (2026). “ATSAC Citywide Adaptive Traffic Signals” — Los Angeles, United States. The Smart City Atlas. https://1001smartcities.org/projects/la-atsac/ (last verified 2026-10-14). Data: CC BY 4.0.

The underlying data is free to reuse with attribution — see the open data page.

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