This week, Istanbul started the process of building the largest monorail network Europe has ever seen. Covering 47 kilometers (29 miles) and ultimately carrying 200,000 passengers a day, Turkey's largest city will one day have a total of eight monorail lines snaking across it, adding missing links to a still-developing transit system.

But despite being one of the largest monorail systems yet constructed (only Chonqqing's is larger), it will be something that the average tourist will most likely never see.

This is because the new network will largely stay beyond the fringes of Central Istanbul. Certainly, it will include one key inner city link (from Beyoğlu to Sisli) and a very welcome connection to Istanbul's second airport, Sabiha Gökçen.

The other lines will be scattered around Istanbul's outlying districts, acting not as major arteries, but as short capillaries feeding passengers into city metro and light rail systems that are themselves still partly under construction. Locals are already debating whether the new network is the most joined-up answer to Istanbul's congestion problems.

Istanbul's rapid transit network, as of September 2014. Maximilian Dörrbecker via Wikimedia Commons. Outsiders, on the other hand, might be tempted to ask something different entirely: Why build a monorail in the first place?

It's fair to say that, compared to streetcar or subway systems, monorails haven't been a roaring success. Sure, they're far from uncommon, and legions of transit nerds have fallen in love with systems like this 114 year-old German beauty.

Still, as their elevated tracks make them more expensive to install than streetcars (and obviously less flexible than buses), monorails have often been written off as impractical to construct. Additionally, because they are typically designed for lighter loads, they carry fewer passengers than a regular train and they still block out the sky just like standard elevated tracks do.

To cap it all off, there are apparently some extra engineering intricacies that come with a single rail. All told, they haven't proved the easiest sell. Some major networks have ended up being dismantled—right now, you can buy bits of Sydney's old monorail on Gumtree.

That doesn't mean monorails aren't a good option if the context is right. The city of Chonqqinq, for example, opted for two monorail lines because hilly terrain and steep valleys would have meant excavating subway lines to depths to which only Jules Verne novels had descended before. Istanbul's reasons for choosing the mode are not dissimilar. A lot of the new network's territory is characterized by sudden dips and rises and/or narrow roads that make streetcars impractical.

These areas are currently served by that staple of many developing cities' transit options—minibuses, which last year accounted for 17 percent of Istanbul's entire mass transit ridership. These may maneuver more easily in narrow streets than regular buses, but they still get snarled up in a thorny briar of endless congestion. They also have a pretty poor reputation for safety, with newspaper Daily Sabah going as far as calling them a "potentially fatal threat due to the reckless behavior of the drivers." By contrast, a monorail could let daily transit literally rise above clogged streets, while its compactness would still cause far less disruption and demolition than a fully-fledged railway.

Traffic in Istanbul, Turkey. REUTERS/Osman Orsal Exactly when the monorails will start clearing Istanbul's roads of traffic is another question. There are no public deadlines as yet, and while Istanbul's transit system is developing fast—the modest, still-incomplete subway system is itself sparkling new in many places—it's not doing so nearly as fast as the city it serves. Given the city's phenomenal recent growth, this is understandable, but at present, the network isn't extensive or joined up enough to coax many citizens away from their cars.

When the city finally completed a rail link beneath the Bosphorus (in extremely difficult conditions) two years ago, it was rightly hailed as a major breakthrough, an engineering marvel that would ultimately move 1.5 million people daily. At present, however, the railway along Istanbul's Asian shoreline that will connect to the tunnel hasn't yet been completed.

Without this connection, daily ridership is a little below 120,000. Given that several of the new monorail lines are designed to feed into this rail link, it'll be a while before the city has transit system truly connected enough to unclog Istanbul's roads.

There's one area where the monorail is nonetheless having an effect even at drawing board stage. As the Turkish press has noted, the monorail announcement is already causing a stir in the real estate sector, sparking interest in sites all along the proposed routes. The plans may be a designed to tame Istanbul's ever growing bulk, but they're also likely to give it the spur to swell that little bit more.