Methodology

Graphic one: Percentage of households without a car in Inner and Outer London, Intramural and Extramural metropolitan Paris (Greater Paris), Manhattan and Outer New York City
Graphic two: Population of Inner and Outer Metropolitan Areas

For Inner/Outer London we used the statutory definition, in which Inner London includes the City of London, plus the boroughs of Camden, Greenwich, Hackney, Hammersmith & Fulham, Islington, Kensington & Chelsea, Lambeth, Lewisham, Southwark, Tower Hamlets, Wandsworth, and Westminster.  

Greater Paris, Métropole du Grand Paris, as defined here, includes all the communes of the departments of the Paris Petite Couronne (Paris, Hauts-de-Seine, Seine-Saint-Denis and Val-de-Marne) as well as seven communes of the Grande Couronne (six from Essonne and one from Val- d’ Oise). 

New York City includes Brooklyn, Queens, Manhattan, the Bronx, and Staten Island.

Data on population were derived from the American Community Survey/US Census for New York, the statistical agency INSEE for both Greater Paris and Intramural Paris, and the Office for National Statistics for London. 

For all datasets, we provided the latest figure available, which unfortunately often refers to different years depending on the different timing in data release for the different cities. 

For car ownership, we used the results of local household surveys. For London, we used the 2019/2020 London Travel Demand Survey; for New York City, we used the American Community Survey 5 years estimates for 2020; for Greater Paris we used the results of the Household automotive equipment survey reported by INSEE. 

Graphic three: Average total annual fatalities between 2015-2019 and percentage of pedestrians, percentage of cyclists, percentage of car users and percentage of powered two-wheel vehicles

For Greater London and New York City, we used yearly traffic fatalities as reported by TfL and New York Vision Zero. Please note the pedestrian fatalities reported by London Vision Zero for 2016, 2017 and 2018 are higher than official TfL figures. For Paris, we used the 2015-2019 averages for Greater Paris reported by the National interministerial road safety observatory. For all cities, car users include taxi users. Only for Paris, car users include all four wheel users. Unfortunately, New York does not provide disaggregated data for powered 2 wheeler users fatalities after 2018. Data for 2019 and 2020 have been extracted from the NYC Open Data and are approximate. See their website for further information.

Graphic four: Estimated PM2.5 contribution by all transport sources

For Greater London, we used the 2020 figure reported by the London Atmospheric Emissions Inventory. For Paris, the latest data available is the 2017 report from Air Parif for the wider Ile-de-France region. Greater Paris accounts for 54.62% of all the PM2.5 in l’Ile-de-France. New York City data is from a 2016 study.

Graphic five: Green Space in Greater London, Greater Paris and New York City

Parks data for New York City comes from the NYC Open Data Portal, alongside additional information from the National Parks Service. For Paris, parks data comes from APUR and from the City of Paris Open Data Portal. London data comes from Ordnance Survey, with the OS Open Data supplemented with Mastermap (because the open data does not include some relevant spaces such as woodland areas). Please note that when comparing green space, definitions are not always identical in each city, although efforts have been made to account for this. Private golf courses and several other similar examples of large private commercial uses (e.g. race courses) initially defined as ‘green space’ have been removed.

Graphic six: Annual average PM2.5 and NO2 air pollution and WHO targets

London and Paris data comes from Isglobal-ranking which uses three different mathematical and empirical models to estimate and compare population-weighted air pollution levels in different metropolitan areas, using as the baseline annual mean PM2.5 and NO2 concentrations at 250 m grid cell level for the year 2015. The values are compared to 2018 values and, although they might slightly overestimate pollution levels, are in line with results by other sources for the year 2019. Unfortunately there is no study available which uses a comparable methodology for New York City so we used the values reported by NYC.gov. These 2020 values are obtained as a weighted average from local monitoring sources.

As visible, no city has yet reached the WHO recommended levels for annual averages (PM2.5 below 5 µg/m3; NO2 below 10 µg/m3). Similarly, all cities continue having more than WHO recommended number of episodes of extreme PM2.5 levels (WHO recommends no more than 3-4 days over 15 mg/m3 average value), as reported by Air Quality in London, Air Parif and, for New York City,  Air Now (please note NYC complies with the American Air Quality Index but not with the WHO targets).

Graphic seven: Space taken up by cars in Greater London, Greater Paris and New York City

We calculated this as the space occupied by the total number of cars owned in the three metropolitan areas, as reported in the vehicle registration data  (see Graphic 14), utilising the size of a standard parking space area (12 sqm in London and Paris, 18.2 sqm in New York).

Graphic eight: Hours lost in rush hour in 2019 and 2021 per commuter driver 

As reported by the Tom Tom traffic index, the figures represent the delay per year with a 30 min commute by car. It is calculated as the “extra travel time during peak hours as compared to a one-hour period during free flow conditions, multiplied by 230 working days per year”.

Graphics nine and ten: Percentage of daily trips on foot and average daily trips by public transport and bicycle in Greater London, Greater Paris and New York City

Data for Greater London are provided by TfL (Travel in London and London Travel Demand Survey) and refer to 2020. Public transport trips include average daily trips by Rail/London Overground, London Underground/DLR, Bus/Tram.  For Greater Paris, the latest data for walking and cycling is from 2018. The data is provisional and refers to the Petit Couronne (smaller than Greater Paris). In the dashboard we used the data as elaborated by Apur. However, for cycling, we can expect recent numbers to be higher as recent reports from bike counts estimate an increase use of bike lanes in Inner Paris to be on average +25% between 2018 and 2019, +47% between 2019 and 2020 and +22% between 2020 and 2021 (For more info see the Paris Municipality website). For public transport, we used the data reported by the Mobility Observatory of Île-de-France. The total trips have been calculated as total average daily trips made by Metro, Tramway and Bus RATP (please note it is unclear whether Tramway trips are on weekdays or weekends). New York City walking figures are from 2018. The total number of cycling trips is from the latest Cycling in the City report for 2020. Public transport trips include total average daily trips by buses, subway and ferry. 

Graphic eleven: Bike share

These are data for shared bikes with a fixed docking station, so don’t include dockless bikes or e-scooters. Data mostly refer to inner cities where bike share facilities are more common. When reporting we assumed 1 hire = 1 trip as different dataset reported figures under  different labels (number of trips, number of hires).  

Graphic twelve: %CO2e per different sectors

For London, we used the 2019 CO2e emissions reported by the London Energy and Greenhouse Gas Inventory. Recent Paris figures are unavailable so we reported the 2017 figure for the broader Ile de France region as presented by Air Parif.  New York City data are from the NYC Mayor's office of sustainability.