Are We Taking Off? A Critical Review of Urban Aerial Cable Cars as an Integrated Part of Sustainable Transport

The scientific literature has predominantly dealt with aerial cable cars as a supplement to public transport for ten to fifteen years; however, a key project that triggered an increased interest was completing the cable car system in Medellín, Columbia, in 2010 [ 31 ]. As a result, the publications included in the review date from 2010 to 2022 without having previously chosen a time limitation in the systematic search. In addition to the temporal distribution, Figure 2 shows the global spatial distribution of existing urban aerial cable cars following [ 17 ]. The data were evaluated with the relative share divided into continents and a subcategory into the functional distinction between public transport (PT) and tourism shown in the second column. In addition to this itemization of [ 17 ], the third column depicts an addition to the origin of the research. The data basis for this was obtained from the publications included in the review, which were examined for the origin of their first author and round-up.

Most aerial cable cars in urban environments are found in South America and Europe, with around two-thirds of the systems in South America serving as a supplement to public transport and, conversely, a similar proportion serving the tourism demand in the European market.

Africa and Asia follow other continents, with African cable cars being integrated mostly as public transport and in Asia as a means of transport for tourism. Few systems exist in North America and none in Australia. The greatest research interest in cable cars comes from Europe, where many research institutes are conducting studies on sustainable transport, and more and more countries are considering the cable car potential. The scientific interest in North America is almost three times as high as the share of cable cars. In contrast, there is proportionally less research with an origin in South America [ 17 ]. This low proportion is, among other things, due to the political structures in South America, as the planning process of “implement and surprise” [ 32 ] often prevails, and where measures are implemented in an exploratory manner without previously examining such in detail.

Subsequently, the above question regarding the scientific assessment of aerial cable cars in urban environments is answered based on the four clusters divided into the following four sections.

Additional work investigated in a Columbian project from Bogotá the local cable car impacts from a health perspective, whereby, environmental influences such as the microenvironment pollution or physical environment were assessed. An interdisciplinary and mixed-method approach included the engagement of policymakers and citizens through an evaluation and design process using various data sources. Data from questionnaires, the air pollution exposure from secondary data, transport trajectories from mobility tracking apps, and direct observations were analyzed, and residents’ perceptions were captured. Pending the project’s final results, this will guide policymakers to counteract negative environmental impacts in highly segregated populations with sustainable mobility. [ 35

A case study from Kuelap, Peru, researched the environmental impacts of introducing a cable car in the Andean landscape. The work addressed cable cars’ unexplored environmental performance compared to other means of transport using a life cycle assessment. The results showed that implementing a cable car compared to conventional road traffic in the orographic conditions of the Andes has substantial environmental benefits. [ 6

A further study examined the effects of transport mobility as a relationship between environmental justice and resilience using the example of the Metrocables in Medellín, Colombia. Even though mainstream transport planning has recognized the relevance of the environment, the combination of considering the socio-environmental effects that do not exclude social issues was not considered enough. The findings revealed that Medellín has undergone noticeable policy restructuring, that is reflected in the city’s designation as one of 100 Resilient Cities; however, the conclusion highlighted that the tension between Medellín as a competitive city in the 100 Resilient Cities challenge and a guiding question on inclusion did not necessarily lead to socio-environmental justice. [ 34

Although there is much research on the accessibility and COemissions of transport systems, only a few studies have been published directly on cable cars. One investigated the COemissions reduction and geographic accessibility in a Colombian case study to shed light on this gap. The work linked the modal shift from established transport modes to cable cars with a socio-economic stratum, it modeled new cable car lines, and simulated the transport consequences. The results showed that implementing cable car lines could save more than 20% of COemissions, and that its ridership could gain up to 10% travel time savings. [ 33

The increasing traffic volumes in cities are not viable in the long term given the current configuration of transport systems, which are facing consequences both for nature and for humans. Consequently, an environmental assessment of the existing systems and expanding new ones are essential core tasks within the global climate targets.

3.1.2. Social Assessment

Social assessment represents one of the most extensive research interests within cable car research, as most publications in this area refer to systems from South America, where cable cars are often designed to foster social inclusion in specific urban spaces; however, although transport systems are generally designed for public and user interests, the social dimension needs to be assessed differently if transport and urban-related conditions differ in other countries.

In the past implementations of cable car systems in Europe, Georgia played a significant role through a cable car network built and extended in Tbilisi between the 1950s and 1980s. A work examined the former ten-line cable car network, that was decommissioned in the 1990s and reactivated in the early 2010s. Data from the transit ridership, field observations, interviews, and document analysis were used to investigate the above. The results showed that the previous network’s planning differed from the current one, where a recent ideological shift in urban policy reflected a government prioritizing global capital and tourism commodification instead of the former transport planning approach. [ 36

Findings for the city of Graz, Austria, showed the potential of a cable car as a supplement to public transport. Conducting mobility surveys, predominantly as stated-preference interviews, delivered data for the transport supplement, and modeled the demand of mobility behavior in a multimodal transport system. The results underlined that a complete integration of a cable car route into the existing transport system showed tourism demand, and that commuters and residents were important user groups. [ 37 ] The insights were insufficient to recommend the integration due to a lack of demand, concerns about a tariff integration and costs, and varying attitudes expressed as part of a public participation process [ 38 ]. A similar approach was taken by a study on a cable car in Munich, Germany, by conducting surveys asking potential commuters and residents close to a considered cable car route in the north of the city about their attitudes. Besides the survey results, which showed an overall positive attitude toward the public transport supplement, the survey data was used in a travel demand model [ 39 ], similar to the approach from Graz [ 38 ]. The model results showed a limited demand for the cable car, and the reasons for this included the short route of the potential system and operating conditions that deviated from reality [ 39 ]. A following study from Munich, which focused predominantly on the planning process of cable cars in Germany via a systematic review and which examined the Emirates Air Line cable car in London, revealed that customer acceptance played a crucial role in the planning process [ 18 ]. A further article provided additional insights into European planning, focusing on Germany. Qualitative interviews with cable car manufacturers, actors from cities, and transport planning experts indicated that the diffusion process of cable cars in Germany was in its early stages; however, after overcoming upcoming obstacles, the chances for cable cars as a part of Germany’s public transport system were high. Major obstacles were identified as a restricted route layout, a lack of concepts on how to connect systems, missing planning routines, and public opposition against investments. [ 27

Like the previously cited European studies, an Italian study underlined the role of tourism when thinking about urban cable cars based on Italian use cases [ 26 ]. Moreover, tourist needs have been evaluated in a further European study investigating the combination of buses with cable cars as feeder lines in the connection between urban areas and tourist destinations in the mountains, with user attitudes distinguished between city residents and domestic and foreign visitors. Cable cars as feeder lines to access urban environments were, according to the results from interviews conducted, revealed as an appropriate alternative to the existing public transport offers, especially as a symbolic effect of being an environmentally friendly travel option. Nevertheless, doubts have remained about the final effect of the modal shift, as the survey results showed only a minor one. [ 40 ] Furthermore, the positive attitudes of potential users in Belgrade, Serbia, were demonstrated by their willingness to pay two to three times the price of a regular public transport ticket for a cable car ride. The motivation for this was based on the ability to overcome obstacles, namely, shorter travel paths, and the unique experience of a cable car ride. [ 41

Like several previous European studies, further work used a stated preference method to explore the potential for a cable car to access the U.S. campus of Boise State University; however, even though the cultural and traffic quality conditions were similar to the European use cases, the results showed that convenience lay above decision variables such as cost [ 42 ].

As stated in the section’s introduction, the social assessment includes the consideration of transport users’ attitudes, changes in the country of application, and a country’s quality of public transport. For example, a study conducted an impact analysis on the potential introduction of a cable car in Baguio City, Philippines. The findings showed that the residents were willing to accept a cable car as a part of the public transport system; however, the current public transport structures were limited, and the transport users relied on informal services that were not a part of the public transport systems in industrial nations. [ 43

This disparity in evaluation became even more apparent when considering the assessment of cable cars in Latin America. One paper of this background analyzed urban transport systems in Latin America and the Caribbean to determine the lessons learned and the challenges. The authors’ evidence on cable cars stated that the systems were generally tourist attractions for visitors from affluent western countries, which take on a different rationale in Latin American cities. The rationale was to establish connections between isolated low-income neighborhoods and city centers. [ 44

Nevertheless, the role of cable cars as the main component of place-branding strategies has triggered a heated debate on how far the systems are considered mainly as a tourist value, for instance, when labelling Brazilian favelas as tourist destinations [ 45 ]. Likewise, further authors followed a similar argument, using the cable car example of Cazucá, Colombia, to highlight the importance of the specific local context. In this case, the most significant impact of the cable car was assigned to the sense of belonging, dignity, and visibility for neighborhoods disadvantaged by long-term politics. [ 46

Although many cable cars exist in Latin America, most evaluations are limited to the Medellín and La Paz applications, and causal evidence is limited [ 44 ]. Essentially, in Medellín, the goal of creating a cable car was to turn the historical reputation for gang and drug-related crimes into a city with greater public safety and inclusiveness [ 47 ]. Therefore, a study did not only analyze the immediate outcomes of the Metrocable, as is usually the case, but focused on placing the cable car within a long-term context of urban transformation in Medellín. Aspects of the national policy, institutional learning, strategic public finance, and multi-sector partnerships were highlighted. The municipality’s comprehensive strategy managed to create a positive presence of the state and maintained the success of the intervention, which has lasted over a decade. [ 47

Further work has confirmed the success of cable cars in Medellín regarding the social dimension. An article underlined the change in the quality of life with the perceived and measured social capital, quality of public infrastructure, and socio-economic well-being after transport developments in Medellín. The results showed that equity in the geographical zones improved even though the specific quality of life dimensions varied. More precisely, the insights showed that a participatory planning process and well-designed public transport interventions improved the social equity. [ 48 ] Additional work analyzed the Metrocables from the perspective of transport engineering, and their impact on crime reduction proved their success revealing the role of cable cars to be key to social integration [ 49 ]. Other authors [ 23 ] verified the prior finding [ 49 ] by investigating the cable car as a part of sustainable city regeneration from former, chaotic, urban growth suffering. The results emphasized that the increase in public spaces and the new transport system has lowered marginality and delinquency [ 23 ].

An additional article evaluated data before and after the cable car implementation focusing on social equity, employment, housing-related costs, and changes in accessibility. The findings showed no statistically valid relationship between housing-costs and the Metrocable, but the main benefits were an improved accessibility to the city’s job market and social equity [ 50 ]. Different authors validated the reduced risk of social exclusion by analyzing the increasing number of trips making and improving a person’s social capital using the Metrocables as an example from a country with a developing economy [ 51 ]. As supplement to this, another work investigated accessibility and its specific inquiry on female residents and their security role. The statistics of origin-destination data from surveys and interviews showed a significant improvement in accessibility for reliability, costs, and travel time variables. Nevertheless, the Metrocable could not overcome all accessibility constraints, as affordability, in particular, is a hindrance, and walking and conventional buses remain the main transport modes. Here, indirect accessibility has played a significant role, as female residents stated that they used the cable car little or not at all due to affordability, but it was emphasized that the stations and the operations entailed general security in the areas. [ 52 ] Another article also raised questions about affordability, as the study indicated that individuals with a lower level of education or from socially disadvantaged classes rarely used the cable car for commuting [ 53 ]. On the other hand, other authors underlined the positive effects of comfort improvements, travel time reductions, and in particular in-vehicle security. These user expectations and perceptions were collected with a panel survey and analyzed using a discrete choice model [ 32 ]. Contrary to previous studies, which showed an increase in safety, some authors did not obtain this result in an analysis of a neighborhood in Medellín, since no crime reduction was revealed [ 53 ].

In contrast to the critical assessment of the prior study [ 45 ] being skeptical of the consequences of favela tourism in Brazil, tourist travel has brought safety benefits to Medellín. Beyond that, the Metrocable has symbolized governmental appreciation for the settlements and has demonstrated public attention [ 52 ]. The symbolic influence was also highlighted by other authors, as they evaluated the Metrocable as initiating a change in planning culture and local politics rather than having a major impact on mobility [ 54 ]. In addition to this and the improved social accessibility factor, additional work even assigned the cable car a pivotal role in transforming informal settlements and their citywide integration [ 55 ]. Medellín has created a model that has delivered urban and social development and allowed neighborhood tourism, which would have been unthinkable only a few years before the Metrocable implementation [ 56 ].

Nevertheless, as a highly visible quick-fix transport technology, cable cars have not been a stand-alone solution to combat poverty [ 57 ]. Other work from different Colombian cities has reached similar conclusions. For instance, a study highlighted that, besides the increased equity in cities due to cable cars, their contributions would have been very limited without complementary investments [ 58 ].

Concluding the social assessment, the research literature gives cable cars a heterogeneous role in urban environments. Western industrialized countries have considered cable cars predominantly as individual measures within highly developed transport systems to serve specific traffic relations. On the other hand, the predominant use cases from Latin America have aimed at integrating disadvantaged neighborhoods into urban structures to promote social equity.