Why aerial tramways are key to sustainable city transport systems

When the his­to­ri­an and crit­ic Lewis Mum­ford said that adding car lanes to deal with traf­fic con­ges­tion was like loos­en­ing your belt to cure obe­si­ty, his sar­don­ic advice was rarely heed­ed. Traf­fic remains one of those facts of life: dirty, con­gest­ed, rage-induc­ing, inevitable.

But pic­ture for a moment the last time you were stuck in traf­fic – grit­ting your teeth, trapped in your car – and imag­ine instead you were sail­ing above it, get­ting from A to B in half the time of that mis­er­able dri­ve.

That may soon be a real­i­ty for Parisians where, from the south-east of the city through to the hilly sub­urbs of Créteil, 10,000 pas­sen­gers a day will be able to use a tran­sit line with a dif­fer­ence: rather than by tram, rail or road, this route will be sus­pend­ed in the air – via a new 4.5km aer­i­al tramway, the Câble 1 (C1), set to open in 2025.

First pro­posed in 2008, con­struc­tion begins this year – con­nect­ing Paris’s pop­u­lous south-east sub­urbs to the Métro Line 8 sta­tion, deliv­er­ing pas­sen­gers into the city in just 17 min­utes.

Faced with a chal­leng­ing, hilly envi­ron­ment and much of the region’s ground-lev­el space already account­ed for – whether by criss-cross­ing high­ways or high-speed rail – Paris decid­ed to build upwards. The cable car route is being built with uni­ver­sal acces­si­bil­i­ty in mind, and despite the soar­ing mode of tran­sit, will be board­ed at the ground floor lev­el – with no need for stairs, esca­la­tors, or ele­va­tors.

“We are con­vinced of the impor­tance of the cable car in an urban envi­ron­ment in com­par­i­son with oth­er modes of trans­porta­tion,” Lucie Cour­saget at Ate­lier Schall, which is design­ing the Émile-Combes sta­tion for the new line. “They’re more eco­nom­i­cal, eco-friend­ly, 100% elec­tri­cal, faster to build – and they’re a pleas­ing means of urban trans­port for pas­sen­gers.”

Unlike the sig­nif­i­cant invest­ment costs and plan­ning headaches asso­ci­at­ed with trans­port infra­struc­ture, build­ing aer­i­al tramways is rel­a­tive­ly pain­less, accord­ing to Inno­va­tion Seil­bahn author Frieder Kre­mer.

“You don’t have to build roads or dig tun­nels, you just need the columns,” he explains. “There’s no require­ment for a lot of large infra­struc­ture. And if it doesn’t work, it’s easy to remove and rebuild them.”

Cable cars are gen­er­al­ly asso­ci­at­ed with tourists ascend­ing ski slopes, but aer­i­al tramways have become a buzzy top­ic of con­ver­sa­tion among urban plan­ners in recent years. As well as Paris, projects are under­way in Lagos, Nige­ria, Domini­ca in the Caribbean, and Dubai, join­ing exist­ing net­works like those serv­ing Ankara, Turkey, Con­stan­tine, Alge­ria, Cara­cas, Venezuela, Medel­lín, Colom­bia, and La Paz, in Bolivia.

In Medel­lín and La Paz, these Tele­féri­cos are inte­grat­ed with the city’s exist­ing pub­lic trans­port net­works, and fer­ry 30,000 and 90,000 pas­sen­gers dai­ly. The out­er reach­es of these metrop­o­lis­es – both locat­ed in val­leys with­in the Andes – were tra­di­tion­al­ly dif­fi­cult for locals to trav­el to and from. With these aer­i­al tran­sit sys­tems in place, pre­vi­ous­ly dis­con­nect­ed res­i­dents were, all of a sud­den, able to access the beat­ing heart of their cities – afford­ing much-need­ed oppor­tu­ni­ties and allow­ing them to more eas­i­ly take part in civic life.

Our cities are set to swell, with some pro­jec­tions fore­cast­ing that 68% of the world pop­u­la­tion will live in cities by 2050 and by 2030, 10 new cities will reach megac­i­ty sta­tus, where pop­u­la­tions top­ple the 10 mil­lion mark. Mobil­i­ty then becomes an increas­ing­ly press­ing ques­tion.

This growth pos­es a chal­lenge for cities new and old. As urban sprawl spreads and tra­di­tion­al road or rail net­works become pol­lu­tant-spew­ing bot­tle­necks, com­mute times become unman­age­able and qual­i­ty of life suf­fers. Mean­while, retro­fitting or expand­ing exist­ing infra­struc­ture in old­er cities often proves com­pli­cat­ed and expen­sive.

“What hap­pens in most cities is that con­ges­tion lev­els estab­lish them­selves at equi­lib­ri­um lev­el, that is, the lim­it of what’s bear­able for peo­ple,” says Alexan­dre Bayen, for­mer direc­tor of the Insti­tute of Trans­porta­tion Stud­ies at the Uni­ver­si­ty of Berke­ley and co-author of the Oliv­er Wyman Urban Mobil­i­ty.

With­out prop­er reg­u­la­tion and care­ful mas­ter plan­ning, these choke points of con­ges­tion can spi­ral out of con­trol. When that hap­pens, cities need to relieve the pres­sure.

Aer­i­al tramways could be one method to man­age this con­ges­tion. For exam­ple – and this is a back-of-the-enve­lope cal­cu­la­tion, says Bayen – a cable car with one cab­in arriv­ing every 10 sec­onds or so, capa­ble of car­ry­ing six peo­ple, could rough­ly mir­ror a sin­gle lane of a reg­u­lar high­way at capac­i­ty.

“It’s not a crazy solu­tion for decon­ges­tion, as long as it’s for very spe­cif­ic local use,” Bayen says. “They’re one way to do demand man­age­ment – but you need to find the right ori­gin-des­ti­na­tion pairs, where they make sense.”

Kre­mer dis­cov­ered that, pro­vid­ed they don’t exceed dis­tances of 7km, aer­i­al tramways are incred­i­bly effi­cient – any­thing fur­ther, and rail­ways are bet­ter. And because they are pure­ly elec­tri­cal sys­tems, they have the low­est emis­sions of any oth­er form of mech­a­nised trans­port. Com­pared to 1.45g per pas­sen­ger kilo­me­tre in cars, a cable car sys­tem mea­sures in at just 0.01g – beat­ing even rail, at 0.02g.

In fact, says Daniel F Mor­ris, clean ener­gy lead at Cli­mate Invest­ment Funds – which is sup­port­ing a new aer­i­al tramway in Lagos, Nige­ria, con­nect­ing Lagos Island to Vic­to­ria Island – pro­vid­ed an area’s ener­gy sys­tem is rel­a­tive­ly clean, cable cars essen­tial­ly plug right into the grid.

“You don’t have to wor­ry about burn­ing diesel,” he says. “And elec­tri­fi­ca­tion, I think, is going to be one of the main ways you see the world decar­bon­is­ing over the next decade or two.”

So if they’re ener­gy-effi­cient and con­ve­nient, why aren’t our sky­lines crowd­ed with sil­hou­ettes of inter­sect­ing cable cars? One pos­si­ble rea­son is as sim­ple as pub­lic per­cep­tion, adds Kre­mer. Because most of us think of cable cars as gim­micky forms of trans­port rel­e­gat­ed to scenic hol­i­day views, they’ve rarely been con­sid­ered a gen­uine­ly use­ful form of urban mobil­i­ty.

Addi­tion­al­ly, while peo­ple think cable cars are only use­ful for cross­ing obsta­cles, this isn’t the case, Kre­mer adds. “If you have two points that should be con­nect­ed, it does­n’t mat­ter if there are hous­es under­neath or a park or a riv­er. It isn’t a require­ment to have phys­i­cal obsta­cles in the way.”

Paris’s C1 project, though, may help to change these per­cep­tions.

For a long time, urban cable cars have been asso­ci­at­ed with prob­lems of alti­tudes, explains Cour­saget. “Cable cars allow much more than serv­ing ter­ri­to­ries with dif­fer­ent alti­tudes, it allows us to cross rivers, high­ways, rail­way lines. Entire neigh­bour­hoods can be opened up in record time, where­as until now, vehi­cles, bus­es and tramways were forced to take long, tedious detours.”

While it’s unlike­ly that our future megac­i­ties will resem­ble a sci-fi sky­line of bisect­ing aer­i­al trams, Bayen notes that these sys­tems could be one effec­tive way to alle­vi­ate mobil­i­ty pres­sure in urban areas.

“It’s not a patch, but some­thing that can improve con­nec­tiv­i­ty on a sur­gi­cal basis, as long as there’s eco­nom­ic via­bil­i­ty to it,” he said. Like home-work­ing, micro-mobil­i­ty and the exten­sion of tram and rail net­works, cable cars could play an impor­tant role in pro­vid­ing a bit of extra breath­ing space in our pro­gres­sive­ly crowd­ed cities.

Near­ly 400 years since Dutch engi­neer Adam Wybe built the first func­tion­ing cable car on mul­ti­ple sup­ports in Gdan­sk, it seems these con­trap­tions may final­ly lift off – con­nect­ing hard-to-reach spots with­in cities, plug­ging gaps in exist­ing sys­tems, and at a frac­tion of the emis­sions costs.