How not to design a flyover

The problems with Bangalore’s infrastructure are well-known. Everybody knows
we have pathetic pot-holed roads, more traffic than the roads can handle, and an
administration that talks through the wrong orifice about fixing things. Heck,
we can boast that we are possibly the only city in the country, and perhaps the
world, that has a traffic light on a flyover, thanks to the wonderful
administration’s short-sightedness.

But apart from the "oh my gawd, we didn’t foresee the hordes of people
moving in" excuse, there are certain problems with the way infrastructure,
is  designed, that makes you wonder if we might indeed have better luck
entrusting the planning work to a large group of chimpanzees, banging away at
AutoCAD. For instance, at some places, you will find bus stops right after a
traffic light. At others, you will find them around corners. This doesn’t need
some genius-level IQ to figure out, for cryin’ out loud. Who in their right
minds can’t see that erecting a bus stop right after a damn traffic light
is a sure way to cause a traffic block? Couldn’t they move it, say, 200 metres

Another thing that the planners don’t seem to understand is the concept of a
"bottleneck". You simply have to look at Old Madras Road, where the 4
lane road is being widened to 8 lanes. Oh, that’s a good thing, you think.
Except that it’s being widened only up to the point of a busy intersection, so
all that happens is that the bottleneck shifts to another point instead.

Let me illustrate this in some detail with the example of the Airport Road-Koramangala
that’s being constructed. This fine piece of work (I almost choked while
writing that) was started in
February 2003 and was supposed to be finished the same year, but of course, all
kinds of bureaucratic problems (methinks somebody didn’t get a big enough share
of the "incidental expenses" pie) led to numerous delays and the first
phase is apparently ready for opening in a fortnight – 3 years later.

The purpose of the flyover is to alleviate the congestion on Airport Road
because the intersection of Koramangala Ring Road, Indiranagar 100 ft Road, and
Airport Road is where three major streams of traffic meet. And anything that can
ease traffic jams is good, right? Flyovers are supposed to help the smooth flow
of vehicles without the problems of having a traffic light, aren’t they? (Unless
you’re using the aforementioned Richmond Road flyover, of course.)

Well… not if you build them like the city of Bangalore does. When a
layperson like me stands in front of the flyover construction site, it’s
glaringly obvious that all the flyover will do is to shift the bottleneck to
another spot: the Indiranagar 100 ft Road.

Take a look at the diagram below. I have colour-coded the different streams.
Vehicles coming from Koramangala are green, the ones coming from Domlur are red,
and the ones going to Koramangala are purple.


Diagram 1


The Indiranagar 100 ft Road is a 3-lane road both ways (and barely one at
that.) The flyover looks like it will have two lanes both ways. This wouldn’t be
so bad, except for the small problem that a bypass from the Domlur side of
Airport Road (marked by "Domlur turn" also ends at pretty much the
same spot. Airport Road is already a busy road, so traffic from there to the
Indiranagar side via the bypass will not be insignificant.

The result: you have four streams of traffic leading into a road
that’s only capable of handling three.

Well, what do you expect when this kind of situation occurs? Some stream will
get blocked. The diagram below shows exactly where traffic will rapidly get
choked (shown in grey.)

Diagram 2


Hmmm, that’s not good at all. Vehicles that are supposed to
move fast over the flyover will slow down considerably, thanks to the choke at the end
of it.



But wait, wait! There’s more. Observant readers may have noticed that
just 30 freakin’ metres away from the termination of the flyover, there’s
a right turn. So you have vehicles coming from the Indiranagar side, wanting to
turn right, and trying to negotiate their way into the right turn, not through
speeding vehicles from the flyover, but through the traffic jam I described
above. Take a look at the new scenario below. Vehicles turning right have been
coloured blue.

Diagram 3


If this is what happens, and keeping in mind the legendary Bangalorean
driver’s consideration for other drivers (cough, cough), the jam will go from bad to worse (see the
expanding grey.)

Ironic, isn’t it, that a flyover designed to make traffic flow faster will do
nothing of the sort? All because some dolts didn’t realise that making four-lane
traffic flow into three lanes creates a choke point.


Let’s take a look at some of the possible options to work around this problem
and figure out how viable they will be.

Option 1) Put a traffic light at the right turn so the blue vehicles can turn
without running into an existing jam. Unfortunately, this is what will happen:

Diagram 4

Yes, if you make flyover traffic wait even 30 seconds for a green light, you’ll have traffic piling up on the darn flyover itself. Oh, and on the
Domlur bypass too. What fun, eh?


Option 2) Seal off the right turn so the congestion is eased. This may help a
bit, but at peak time, say 6-7 PM, when traffic doubles or triples, you will see
the heightened effect of four lanes flowing into three. Here’s what you’ll get:

Diagram 5

You now get two congestion zones instead of one. Worse, you risk the Domlur
bypass pile-up to propagate on to the main airport road itself, and that just
puts us back at square zero.

Lastly, after all this, I guess I should point out that the numerous traffic
light stops and intersections on 100 ft. Road will make it difficult for fast streams of traffic
to progress, with the result that the entire 2 Km stretch will be perpetually
jammed like Cunningham Road currently is. That is the domino effect, amigos.

Suddenly those chimpanzees using AutoCAD seem like a better proposition,
don’t they?


I am no road planner, but as someone who’s done a wee bit of programming in
the past, I have some understanding of bottlenecks and scalability. The
Koramangala-Indiranagar flyover looks like a disaster waiting to happen when
it’s thrown open to the public on July 15. It’s a pity that spending millions of
rupees wasn’t enough to get someone half-sensible to design the darn thing well.


(I hope to start a small series soon on how traffic jams are caused in
Bangalore. This will hopefully bring me out of my blog drought, caused by life
giving me a hard time from all corners lately.)

Update: It seems the stupid politicans have already started damaging the flyover

21 thoughts on “How not to design a flyover”

  1. Bangalore ain’t the only city with a traffic light on a flyover.
    You see, if Bangalore does something, Madras only does it better.
    Madras put a traffic light on top of a flyover – but to be fair, the light does help co-ordinate traffic better.
    But there are two overpasses, over railway lines, that have traffic lights right at the end…which means traffic piles up on the brige itself.

  2. this is way too scientific for me, but i can appreciate one thing – the diagrams are fantastic! okay, kidding. but i think you should change your profession to road and urban planning now. or at least get onto some committee :)

  3. i always thought this flyover was way too small in vision and design….and. that road needs a flyover all the way to airport.
    they could have mad one parallel road to airport but i guess govt wanted to give land to it companies there maybe.

  4. Diary circle flyover/underpass is similar (though not this complex). Right after the underpass (towards BTM on Bannerghatta road) there is a bottleneck. Plus a small road joins the main road causing more vehicles and turns.
    I was optimistic then!

  5. Great post. On an average, flyovers are bad responses to traffic mismanagement. Unless they are long flyovers, or clover leaf ones or a parclo interchange. Further, in urban spaces – they aren’t always adviced. But I suppose where roads cannot be widened – they provide respite.
    Delhi’s flyovers work because they are on the arterial roads – which are wide enough to accomodate an upper level of traffic streaming with a lower one. Bombay – it’s a nightmare.
    :) Maybe urban planning should be left to bloggers!

  6. Madhu, we met @ Shiok [along with Nitin, Atanu & Sandeep a month or so ago]. Nice coincidence this. I was going through 100 ft. road this evening and wanted to get to my workplace in EGL Business Park (start of inner ring road). Due to this fly over, I had to take that aforementioned right and then get to work through Airport Rd.
    Before I took the right, I saw the signboards on the flyover. One indicated left to Airport … fair call. Another indicated straight to Koramangala … fair call. The last one was the most interesting. It indicated right, and had a curve in it. So I assumed there was a part of the fly over which’d nicely lead down into Airport road somewhere.
    Imagine my shock when I saw nothing of that sort on Airport road.
    I’m hoping I’ll never have to use the fly over to get into 100 ft. road, after reading your post!

  7. madman,
    Must give it to you for painstakingly analysing this scenario. Point well taken. Let me give you my two cents worth since it’s up my alley (pun unintended).
    First off- YIKES!!!!
    I can’t believe the attached photograph of the proposed overpass or flyover. Please tell me that some kids built it for their school project.
    The Dulmur Turn you are talking about doesn’t seem to merge on the flyover (according to model), but to the Indiranagar Rd below.
    In case I were to trust you on that, lets say at this point, Option 2 is the best solution if it is designed right (right being subjective to different design standards).
    “you have four streams of traffic leading into a road that’s only capable of handling three. ”
    It’s Ok for four strams of traffic leading to a road that is capable of handling three as long as the traffic that is entering is below the capacity of a three lane roadway. In this case maybe not. The solution would be to widen Indiranagar Rd to 4 lanes after the Dolmur Turn merge(duh? Rocket science!)
    I still don’t get that model.
    Like Ravages pointed out, it’s a miracle how those flyovers in Madras actually work. Very soon they wont.
    Option 3: Buy a bicycle.

  8. Aah, you’re thinking too logically, thus you’ll never be employed by the BDA.
    The problems you mention are real and the authorities will realise it in 9 and a half months.
    Their solution would be simple to the point of making your post seem silly and a utter waste of time – they’ll reverse the direction of all the lanes of the flyover. Traffic will slow down automatically due to the confusion and all congestion will vanish.

  9. Well, seems like its been money well spent….hehe, i remember your post where you had mentioned that the earlier CM saying that the roads were bad and left like that cause that slows down traffic and hence lesser accidents!! haha…good one…..and yes, whats with the curly kinda arrow on the flyover…..
    i guess we can start calling it a crawlover from now onwards…its already been a crawl to finish

  10. If all goes ?well?, a successful Airport Road fly-over will end up choking traffic at Koramangala 80 ft road, Indiranagar 100 ft road, and the signal near HAL (near Airport exit point).

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  12. Thats a cool analysis, Madhu..
    Its very simple the idea is to shift the traffic from one point to another point..
    the U-Turn on top of flyover is a design whhich not many designers would have thought of. was this design made to make money or to show the architectural stupidity??

  13. madhu, it may not be such a bad idea after all. usually what they do is to have light s on the flat roads to stream the traffic smoothly. they can have lights on the domlur turning, and towards the left of the flyover landing to the 100ft road. a 10 sec traffic lights can do wonders. but knowing the dumb planning going all over the city, you may be right. perhaps it would be nice if you are proved wrong. anyways, now that it is open, how is it fairing? (btw, i have cancelled my bangalore trips till i get a report from you)

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