2023 City Index for Mindful Travellers

Most of us think about sustainability when we travel - and that includes city travel! We've analysed 28 factors that sustainably-minded travellers are likely to consider – from how to get to a city to what activities to do. See which of the 167 cities included give the most options for travellers, and learn more about the factors that were considered here.

Not your typical city ranking

What makes this ranking different from other city lists you might've seen? Ours has you, the sustainability-minded traveller, top of mind. We've grouped 28 factors into four categories that take a 'traveller-first' perspective, to give you a more complete idea of how you can thoughtfully select a city destination.Have a go with the ranking table below and see how you can customise it according to your priorities. You can get more info on the ranking's background, factors and data in the Methodology section.

Sustainability-related factors considered during a trip

Travelling toPre-arrival factors such as options for ground travel, flying off-season or landing at a carbon-accredited airport.

Getting aroundFactors here include public transport options, affordability of more eco-friendly car hire, number of biking and walking routes, wheelchair accessibility, etc.

StayHow attractive it is to stay in the city: air quality, drinkable tap water, availability of hotels with the Booking.com Travel Sustainable badge and their pricing levels, etc.

ExperiencesExperiences that support the environment and community, like shopping at local markets and second-hand shops, taking walking tours, visiting cultural attractions, etc.

Top 3 cities for sustainably-minded travellers:

1. Rotterdam

Final score: 100

Rotterdam, Netherlands took the grand prize as the most ideal city for sustainably-minded travellers. This city topped the charts because it's not over-touristed and you can fly there in the off-season month of January for 59% les ...

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2. Amsterdam

Final score: 93

Despite being a more popular destination, Amsterdam came in at a very impressive No. 2 spot in our rankings. Its airport has a high accreditation level, it offers lower-emitting transport options like ferries and trains, has low c ...

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3. Graz

Final score: 91

Graz, Austria is a hidden gem that has managed to slide into the No. 3 position as an intriguing destination for travellers with sustainability close to their hearts. Its well-developed rail network makes it easy to travel there b ...

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Reset all filters

Customise your city comparison above: choose the destinations and factors that you're most interested in and your chosen cities will be re-ranked.

Click on a category column below to expand it and see individual factors. Click on a factor's arrow to sort the ranking based on that factor.

Rank

City

RotterdamNetherlands

AmsterdamNetherlands

GrazAustria

TrondheimNorway

MunichGermany

HelsinkiFinland

StockholmSweden

ZurichSwitzerland

GothenburgSweden

ViennaAustria

Final score

100.0/100

93.9/100

91.4/100

88.9/100

86.8/100

85.7/100

81.4/100

79.1/100

76.2/100

74.6/100

Travelling to

97/100

87/100

59/100

76/100

100/100

89/100

78/100

98/100

73/100

Getting around

89/100

100/100

88/100

75/100

73/100

85/100

81/100

70/100

71/100

Stay

87/100

77/100

81/100

100/100

96/100

60/100

81/100

82/100

79/100

73/100

Experiences

75/100

49/100

100/100

67/100

73/100

49/100

33/100

63/100

26/100

60/100

Methodology

Data across 28 factors has been collected to rank cities in terms of possibilities available for sustainability-minded travellers. These factors have been grouped into four categories that reflect the main areas of consideration when planning a city trip: Travelling to, Getting around, Stay and Experiences.

Rather than taking a broad spectrum of sustainability aspects, the study focuses on those factors that are directly related to the travel experience for the sustainability-minded visitor, thereby ranking cities accordingly.

In May 2022, KAYAK conducted an e-survey among 10,000 participants from the USA, Canada, Australia, Austria, Germany, Denmark, Spain, France, Sweden, and the UK via Cint’s panels. This survey revealed that around 83% of people say sustainability influences their summer 2022 travel plans - but around 55% feel there is a lack of travel options that they considered to be ‘sustainable’, and more than a third find it hard to make sustainable choices while on holiday. This shows that travellers seem to have sustainability top of mind when planning, but aren’t always able to fulfill their sustainability goals.

Subsequently, KAYAK conducted this data study in order to determine the options that a mindful traveller may have in a given city and show the traveler more sustainable actions they can take during their city trip. This project is based on a literature overview of sustainability, overtourism and related extensive data collection from a variety of sources. We’ve ranked 167 cities according to 28 factors that sustainability-focused travelers may take into account when making travel choices along the journey - from transportation options to the destination all the way to what activities the traveller can enjoy while there. Please, refer to the detailed factor descriptions below (‘Data sources & factor definitions’), as well as to the list of sources for theoretical background under ‘Literature’.

The factors were based on the three pillars of sustainability: environmental, socio-cultural and economic (Barbier, 1987). Similarly to Barbier, 1987, we also acknowledge the difficulty and discourse around operationalising sustainability, while for purposes of usefulness and simplicity we have chosen this most widely referenced framework in the field. When applying the ideas to tourism we additionally rely on the UNWTO guidelines of sustainable development. Factors based on the environmental pillar are those that refer to greenhouse gas emissions reduction, air quality and consumption of water, land and energy. Socio-cultural based factors are those that deal with the local people, community and culture preservation. Economic-based factors are those that support the local economy and keep money local. Some factors may relate to more than one pillar.

The Travel Sustainable programme is a Booking Holdings programme designed for accommodation property owners that qualify for the programme by implementing practices that lower their environmental impact (like not using single-use plastics or investing in renewable energy) and that support local communities (such as putting money back into community projects and providing green spaces). For more information, please click here. We refer to such properties as ‘Travel Sustainable hotels’ in this index and methodology.

The most searched hotel city destinations worldwide have been identified based on searches conducted from 2021 Jan 01 - 2022 Mar 01 for the travel period 2022 Jan 01 - 2022 Dec 31. Then top cities per region and country were shortlisted to account for an even geographical representation. Finally, cities were further shortlisted based on data availability, which resulted in inclusion of a total of 167 cities in this analysis.

1. Weights: 24 out of the 28 factors have been assigned a weight indicating their importance (1 - lowest, 4 - highest). The factors dealing with share of Travel Sustainable hotels in a city, price difference between Travel Sustainable- and non-Travel Sustainable hotels, carbon accreditation of airports and levels of connectivity in ground transport (rail and ferries) are considered to be stronger indicators of options available for sustainability-focused travellers and were, therefore, assigned the highest weight (4). They are closely followed by factors related to local traffic as well as air quality and city attractiveness for longer stays. These high weights have been assigned to factors that seem to be most relevant regarding issues around overtourism (Peeters et al, 2018; Milano et al, 2019; Gossling et al, 2018; Oklevik et al, 2021). Lower weights have been assigned to factors in the Experience category, those related to infrastructure for getting around in the city as well as other factors that are not considered to be the main sustainability-related decision drivers of choosing a travel destination.

Seasonality indicator: The importance of flight price difference between peak and off-season has been weighted individually for each destination based on a seasonality level, which was calculated as a ratio between high and low search months.

Bonus points: Binary factors, including: Drinkable tap water, World Heritage Cities, Free walking tours and Commitment to Diversity & Inclusion were calculated as bonus points, i.e. a city would receive +1 extra point for any of these factors, with a maximum of 4 extra points. Similarly, for “Urban rail transit” a city would receive up to 3 extra points for having a high number of rail transport options.

2. Values within each factor were firstly normalised using formulas: score = 10 * (x - min(X)) / (max(X) - min(X)) and score = 10 - 10 * (x - min(X)) / (max(X) - min(X)) for inverted values (e.g. the amount of estimated car traffic in a city, where the lower percentage value is better).

3. The weighted average score of the factors has been calculated for each city.

4. Lastly, the weighted average score of the factors has been normalised using the formula score = 99 * ( ( (x - min(x) ) / ( (max(x) - min(x) ) ) + 1 to reach the final score on a scale between 1 and 100 (with 1 being the lowest and 100 the highest score).

The same procedure has been applied separately for scores within individual categories to determine category-level scores:

The ‘Travelling to’ category comprises four factors related to the choice of a destination and travel period (with possible mitigation of overtourism (Peeters et al., 2018; Milano et al., 2019)), as well as transportation mode (with possible reduction of associated carbon emissions):

Destination popularityShare of global hotel searches in a given city out of all hotel searches in the cities included in the analysis. Number of searches based on the search period June 2021 - August 2022 for travel period August 2021 - July 2022. Source: KAYAK internal data (retrieved on 2022 Sept 08)

Seasonal flight price differenceScaled percentage difference in flight prices between the highest and the lowest searched months across domestic, international and intercontinental flight routes. The bigger the price difference between peak and off-season flights, the better, as this encourages flying in off-season. Travelling during the off-season may have environmental and social benefits, including, but not limited to, not contributing to environmental pollution during high season, and reducing demand on infrastructure during high season. The importance of this price difference for the final score has been adjusted according to the destination’s seasonality, described in the ‘Scoring system’ section. Prices are based on searches conducted in the period June 2021 - August 2022 for travel period August 2021 - July 2022. Source: KAYAK internal data (retrieved on 2022 Sept 08)

Airport Carbon AccreditationA carbon management certification standard for airports. There are 6 levels of accreditation with 6 being the highest. Calculated is the average level across all airports and around in the city. Source: Airport Carbon Accreditation (retrieved on 2022 Sept 08) “Airport Carbon Accreditation is the only institutionally-endorsed, global carbon management certification programme for airports. It independently assesses and recognises the efforts of airports to manage and reduce their carbon emissions through 6 levels of certification: ‘Mapping’, ‘Reduction’, ‘Optimisation’, ‘Neutrality’, ‘Transformation’ and ‘Transition’.“

Trains and ferriesLevel of connectivity from 1-5 based on the train and ferry routes in a city, where level 1 indicates poor connectivity of city by train or ferry routes, and 5 denotes excellent connectivity. Calculated as absolute number of routes (tagged in OpenStreetMap) scaled by relative city size. Source: OpenStreetMap (retrieved on 2022 Sept 21). OpenStreetMap is a free, open geographic database updated and maintained by a community of volunteers.

The ‘Getting around’ category comprises nine factors related to local mobility trends and infrastructure:

Popularity of carsEstimated share of car use for work or school commute by the locals out of all transport modes. Source: Numbeo (Accessed on 15.09.2022). “Numbeo is a collection of Web pages containing numerical and other itemisable data about cities and countries, designed to enable anyone to contribute or modify content. Numbeo uses the wisdom of the crowd to obtain the most reliable information possible.”

EV charging stationsThe estimated number of EV charging stations for cars per mi2. Source: OpenChargeMap and OpenStreetMap (retrieved on 21.09.2022). “Open Charge Map is a non-commercial, non-profit, electric vehicle data service hosted and supported by a community of businesses, charities, developers and interested parties around the world.”

Price difference: Eco-friendly car hirePercentage difference in eco-friendly (hybrid or electric) vs non-eco-friendly car hire price in a city. Prices based on the search period June 2021 - July 2022 for travel period August 2021 - July 2022 across all car types. Source: KAYAK internal data (retrieved on 06.09.2022)

Popularity of bikesEstimated share of bike use for work or school commute by the locals out of all transport modes. Source: Numbeo (Accessed on 15.09.2022)

Bike sharingThe estimated total number of shareable bike hires across available operators in a city. Source: Bike-sharing World Map (retrieved on 06.09.2022). “A map of the world's bikeshare services (short-term bicycle hire available at a network of unattended locations).”

Bike routesCalculated is the length (mi) of bike routes per mi2 in a city. Source: OpenStreetMap (retrieved on 21.09.2022)

Urban rail transitBonus point system on a scale 0 - 3 (low-high), indicating the level of alternative public transport infrastructure, based on the total number of tagged subway, tram, trolleybus, light rail, monorail, and funicular routes. 1 point was given for over 4, 2 points for over 10, and 3 for over 40 routes. Source: OpenStreetMap (retrieved on 21.09.2022)

Pedestrian-only roadsCalculated is the length (mi) of pedestrian-only roads per mi2 in a city. Source: OpenStreetMap (retrieved on 21.09.2022)

Wheelchair accessibilityThe number of tagged wheelchair-accessible places in a city, converted to a 4-level scale. The higher the level, the more wheelchair-accessible a given city is. Level 1 indicates less than 0.3 tagged wheelchair accessible places per square kilometre, level 2 denotes 0.3-1.3 per mi2, level 3 1.3-2.6 per mi2, and level 4 is more than 2.6 places per mi2. Source: OpenStreetMap (retrieved on 21.09.2022)

The ‘Stay’ category comprises six factors related to the length of stay, types of accommodations, and living conditions and habits:

Longer staysPresented is the average length of stay, which is treated as an indicator of how attractive a city is for longer stays. Longer stays may help promote social and economic sustainability because travellers have the time to go beyond the city centre (e.g. shop in local businesses on the outskirts), and help support more communities through tourism (Gössling et al, 2018; Oklevik et al, 2021). The average length of hotel stays (number of days) in a destination city, based on search period January 2021 - August 2022 for travel period September 2021 - September 2022. Source: KAYAK internal data (retrieved on 07.09.2022)

Hotel availabilityShare of Travel Sustainable hotels (Travel Sustainable Program, from Booking.com) out of all properties in a city. Source: KAYAK internal data (retrieved on 30.07.2022)

Hotel price differencePercentage difference in price between Travel Sustainable (Travel Sustainable Program, from Booking.com) - and non-Travel Sustainable hotels (Travel Sustainable Program, from Booking.com) in a city. Prices based on the search period June 2021 - July 2022 for travel period August 2021 - July 2022. Source: KAYAK internal data (retrieved on 08.09.2022)

Air qualityAverage Air Quality Index (AQI) for a city from the year 2021; scale 1-500 (best-worst). Source: Air Matters. “A global air-quality service provider: Providing real-time Air Quality Index & Allergy Pollen & Weather Data, as well as Protection Recommendations and Forecast.”

Recycling pointsThe number of tagged recycling points in a city, converted to a 5-level scale. The higher the level, the more recycling options there are in the city. Level 1 denotes less than 0.1 tagged recycling points or centres per square kilometre, level 2 indicates 0.1-0.5 per mi2, level 3: 0.5-1.3 per mi2, level 4: 1.3-2.6 per mi2, and level 5 more than 2.6 recycling points per mi2. Source: OpenStreetMap (retrieved on 21.09.2022)

Drinkable tap waterBinary variable indicating whether tap water is generally considered drinkable or not in a destination (country level).Source: CDC (accessed on 02.09.2022)

The ‘Experiences’ category comprises nine factors related to a range of things to do, accessibility & inclusion as well as cultural experiences for travellers:

Walking toursShare of city walking tours out of all sightseeing tours offered in a given city. Source: KAYAK internal data (retrieved on 09.08.2022)

Free walking toursBinary variable indicating whether free walking tours by locals are offered in a city and if they can be easily found on the internet. Source: Research based in August 2022

Wheelchair-accessible toursShare of wheelchair-accessible tours out of all tours offered in a city. Source: KAYAK internal data (retrieved on 09.08.2022)

Commitment to D&IBinary variable, indicating city’s commitment to Diversity & Inclusion by being a member of the International Coalition of Inclusive and Sustainable Cities (ICCAR) and/or having an undersigned declaration to combat hate, extremism and bigotry. Source: UNESCO ICCAR, The United States Conference of Mayors (as of 28.03.2022). “The International Coalition of Inclusive and Sustainable Cities - ICCAR was launched by UNESCO in 2004 to assist local authorities in combating discrimination in their capacity as policy maker and service provider in areas as diverse as education, employment, housing provision and cultural activities.”

Local marketsThe number of tagged marketplaces per mi2. Source: OpenStreetMap (retrieved on 21.09.2022)

Second-hand shopsThe number of tagged second-hand shops of all kinds in a city per mi2. Source: OpenStreetMap (retrieved on 21.09.2022)

World Heritage cityBinary variable, indicating whether a city is a member of the Organisation of World Heritage Cities. Source: Organization of World Heritage Cities (retrieved on 19.08.2022)

Museums and artThe number of tagged museums, galleries, art shops, and art centres in a city per mi2. Source: OpenStreetMap (retrieved on 21.09.2022)

TheatresThe number of tagged theatres in a city per mi2. Source: OpenStreetMap (retrieved on 21.09.2022)

2023 City Index for Mindful Travellers

Not your typical city ranking

Sustainability-related factors considered during a trip

Top 3 cities for sustainably-minded travellers:

1. Rotterdam

2. Amsterdam

3. Graz

Methodology

Study approach

Background

Travel Sustainable (Booking Holdings programme)

City selection

Scoring system

Data sources & factor definitions

Travelling to

Getting around

Stay

Experiences

Hotels