Permanent project revision
Revision 2026-08-20-source-dates-r2 · effective 2026-07-26
Superseded. A later revision exists: 2026-08-27-landmark-p6-uplift →
Record the publication date of each source that states one; sources that publish no date are marked null.
sha256:0d4b5d16e637a304290540b651f6dabe06dd35332a69292480e71279412ca6b6
replace /snapshot/projectFingerprint — Updated projectFingerprint to the current sourced project record.replace /snapshot/sources — Updated sources to the current sourced project record.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.
clm-c05142d557d70a65
quantitative
Davis (Journal of Political Economy 116(1), 2008) found 'across pollutants and specifications there is no evidence that the restrictions have improved air quality', together with evidence that the ban raised the total number of vehicles in circulation and shifted the fleet toward high-emission cars.
clm-6154072a52ebdd2b
quantitative
Mexico City started keeping cars off the road one weekday a week by the last digit of their plate in November 1989, after an ozone emergency, and made the rule permanent the following year
clm-d81cf531abf232f9
quantitative
It began on 20 November 1989 as an emergency measure named ‘Un Día sin Auto’
clm-ee48b27635074471
quantitative
A compulsory emissions test every six months assigns each car a hologram, and that reading decides how hard the ban bites: holograms 00 and 0 drive every day, hologram 1 also rests two Saturdays a month, hologram 2 every Saturday
clm-b110d027832a161a
descriptive
When the metropolitan monitoring network pushes ozone past the contingency threshold the regional environment commission declares a ‘Fase I’ that pulls even exempt cars off the road
clm-aaf51da274454a23
quantitative
CAMe activated five ozone Fase I contingencies in 2025 alone
clm-0b5f70ac48d9cee9
descriptive
‘across pollutants and specifications there is no evidence that the restrictions have improved air quality’
clm-31c3f86ab4d2e7aa
descriptive
evidence that the ban raised the total number of vehicles in circulation and shifted the fleet toward high-emission cars
clm-26c8718fff3952dd
descriptive
an initial drop in car use followed by a rise in the household vehicle stock within eleven months
clm-a2d6ea97cf37a835
quantitative
the July 2008 Saturday extension had virtually no discernible effect across eight pollutants, and no sign that drivers switched to metro, bus or light rail
clm-d8a858260451ab03
descriptive
drivers shifting trips onto lightly policed roads
clm-123a2c9c7699aada
descriptive
Press reporting describes photo-enforcement cameras in Mexico City that sanction Hoy No Circula violations as well as speeding
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.
Awaiting operator and domain-expert review; publication of this revision implies neither.
sha256:0d4b5d16e637a304290540b651f6dabe06dd35332a69292480e71279412ca6b6
src-ace305ebc8ebcd24The load-bearing null result, abstract verbatim: 'In 1989, the government of Mexico City introduced a program, Hoy No Circula, that bans most drivers from using their vehicles one weekday per week on the basis of the last digit of the vehicle's license plate... Across pollutants and specifications there is no evidence that the restrictions have improved air quality. Evidence from additional sources indicates that the restrictions led to an increase in the total number of vehicles in circulation as well as a change in composition toward high-emissions vehicles.' Publisher page journals.uchicago.edu/doi/10.1086/529398; the author's own copy is at faculty.haas.berkeley.edu/ldavis/Davis%20JPE%202008.pdf but did not render from this desk, so the abstract was verified against this indexed mirror.
src-78b678356a3b5670Dates the Saturday extension and grades it: 'Mexico City's driving restrictions were expanded to include Saturdays on July 5th, 2008.' and 'Overall, there is little evidence that the program expansion improved air quality.' Also the sentence this entry uses on enforcement: 'City police vigorously enforce the restrictions and vehicles violating the ban are easy to spot. Drivers caught violating the rules must pay a hefty fine and their vehicles are impounded for 48 hours.'
src-1aed7de45827ff4bIndependently dates the programme to November 1989 and measures the second-car response: an expected short-run fall in car use followed by a rapid rise in the household vehicle stock inside eleven months, with a transport cost put at about 5 per cent of the value of the vehicle stock at implementation. Cited for the rebound, not for any air-quality figure.
src-7d81a556f40673acThe operator's own programme page and the correct citation for the current rules. Direct fetch returned 503 from this desk on 2026-07-26; the rules were corroborated against the CAMe description and the 2026 press cited below, which agree on hours, coverage and hologram tiers.
src-debbf8eec8ff1891The metropolitan authority's own description, carrying the coverage and hours used in the snippet: 'Aplica en las 16 alcaldias de la Ciudad de Mexico y en 18 municipios conurbados del Estado de Mexico, de lunes a sabado de 5:00 a 22:00 h' ('It applies in the 16 boroughs of Mexico City and in 18 adjoining municipalities of the State of Mexico, Monday to Saturday from 5:00 to 22:00'), and the hologram rule: 'Los vehiculos con holograma 1 no circulan dos sabados del mes segun su terminacion, mientras que los vehiculos con holograma 2 no circulan ningun sabado del mes' ('Hologram 1 vehicles do not drive on two Saturdays a month according to their plate ending, while hologram 2 vehicles do not drive on any Saturday'). Direct fetch blocked (403); the carrying sentences were confirmed by search.
src-ad142b48dbcb7470Establishes who declares a contingency and that a declaration extends the driving ban. CAMe activated five ozone Fase I contingencies in 2025 alone (26 February, 18 March, 1, 23 and 25 April). The activation threshold is reported by Mexican press as 150 IMECA points for ozone, with a pre-contingency at 135, at which point 'Doble Hoy No Circula' reaches holograms 0 and 00; that numeric threshold is press-reported and is deliberately kept out of the snippet. Direct fetch blocked (403).
src-afdaf4d2258b3ff4Origin detail: the programme began on 20 November 1989 as an emergency measure named 'Un Dia sin Auto' ('A Day Without a Car') during an ozone emergency, and was made mandatory and permanent by an accord published on 1 March 1990, alongside the introduction of biannual vehicle emissions verification. The exact 1990 date rests on Mexican press rather than on the Gaceta text, so the entry says only 'the following year'.
src-6d20cebdd4a72790The camera question, media-grade only: 'Estos dispositivos no solo sancionan a quienes exceden la velocidad, tambien detectan conductores que circulan sin respetar las restricciones ambientales' ('These devices do not only sanction those exceeding the speed limit, they also detect drivers circulating without respecting the environmental restrictions'), on a network described as more than 140 fixed cameras and radars plus mobile units, after CDMX restored economic photo-fines alongside the 2019 points-based fotocivicas. No official source confirming camera detection of Hoy No Circula was reachable, so this is not claimed in the snippet.
src-344cf108280f6545Peer-reviewed follow-up on how drivers evade the ban, including shifting trips onto lightly policed roads. Publisher page blocked (403) from this desk; listed for existence and topic. No figure in this entry rests on it.