Road widening – road to nowhere

The next time you’re on the road at peak traffic time observe this. There’ll be a wannabe Michael Schumacher who’ll take off like a rocket at the signal, and you’ll meet up with him at the next signal. You’ll most likely meet up with him at every signal over the next 10 km.

Why does this happen, even though he’s driving faster than you? This is because of the ‘Schumi-Bang effect’, a scientific phenomenon caused by the interaction between Schumi’s vehicle and Bangalore’s roads. Here’s the explanation.

When traffic signals are close to each other, your average speed depends on how long you stop at a signal rather than on how fast you travel between signals. You don’t have to be a transportation engineer to figure out why. All you need is some primary school arithmetic skills.

Let’s assume you and Schumi leave a traffic signal at the same time. The next signal is ½ km away, and is for a duration of 1.5 minutes (90 seconds). The next signal turns red just as both of you leave the first signal. Schumi travels at 60 km/hr, reaches the next signal in 0.5 minutes (60 km/hr means 1 km per minute, so half a minute for half a km), waits for 1 minute for the light to turn green. You travel at 30 km/hr, reach the next signal in 1 minute, wait for 0.5 minutes for the light to turn green. When the light turns green, both of you leave the signal at the same time.

This repeats itself signal after signal, and after a distance of 10 km you’re probably still abreast of each other. In reality, many of the busier traffic junctions may have a wait time of 3 minutes (180 seconds), and in heavy traffic you may have to wait for the light to turn green twice before you clear the junction. So the effect is even more.

I commute to work by bicycle. In an extreme example of the Schumi-Bang effect, I often keep abreast of a Schumi at every signal almost the whole distance from my office to my home. At peak traffic time it takes me 1 hour from home to office by car, and it takes me the same 1 hour on my cycle. At every signal the cars and motorbikes bikes reach before me and wait, and I eventually draw abreast of them.

Wider roads are the only solution, right ?
Wrong !
Widening a road enables you to travel faster between signals. Widening a single lane road to a double lane road, for example, would double the speed between signals. As we’ve seen in the above example, however, doubling the speed only doubles the wait at the next signal.

The problem is not the speed between signals. It is the wait at the signals. The solution therefore is to reduce or eliminate waiting time at signals.

We have living proof of this in Bangalore.
Example 1:
Sankey Road between Golf Club and Mehkri Circle was notorious for traffic jams.
When Cauvery junction underpass was built, the problem disappeared. A month after this BBMP started widening Sankey Road between Golf Club and Windsor Manor, from two lanes to three lanes each way. Traffic signals at Windsor Manor and BDA junction were removed. Traffic from Bellary Road was diverted to Palace Road. During this construction phase the road adjoining golf course was actually reduced to one lane because of digging and debris. But guess what? There was no difference in traffic speed, even though the road was narrowed instead of widening.

Example 2:
Hosur Road beyond Silk Board was widened to 3 lanes. The traffic congestion should have disappeared, but it did not. Again because of the Shumi-Bang effect. Many stretches of the road are actually single lane because of the construction of the elevated road. When you drive down the road now, you are coasting along at a reasonable speed till you hit a traffic intersection. There’s a traffic pile-up at every intesection, and only at intersections. The problem again is not the road width, it is the intersections.

Sankey road

Sankey Road reduced to single lane during construction, near Hotel Meridien on Sankey Rd. Showing no congestion at 6 PM, peak traffic hour, on a working day. Pic source: G V Dasarathi.

Cauvery junction

Traffic near Cauvery junction showing no signs of congestion at 6 PM, peak traffic hour, on a working day. Pic source: G V Dasarathi.

BBMP knows about the Schumi-Bang effect

In response to an RTI application dated May 22, 2008, the Assistant Executive Engineer, Special Cell for Subways, replied with these details:

Before the Cauvery theatre underpass was built the average waiting time of traffic at the Cauvery theatre signal was 180 seconds. The waiting time now, after the underpass was built, is zero seconds.

Before the underpass was built the average speed of vehicles between Bangalore Golf Club and Mehkri circle was 10 km/hr. The average speed now is 30 km/hr.

30 km/hr, by the way, is a good speed for inner city travel by international standards. What we note is that this increase in speed was while Sankey Road was being widened, when the BDA junction was not yet ready, and traffic was being diverted through a narrow single-lane side road in Kumara Park.

The obvious conclusion is that removing the traffic intersection at the Cauvery theatre by building an underpass made the big difference, not road widening.


How do we avoid stops at intersections ?

Option 1 – Coordinated signals

Coordinated signals are a series of signals that work in such a way that vehicles can proceed through a continuous series of green lights.

Let’s now design a simple coordinated signal system for a 2 km long main road on which there are signals every 0.5 km and we want vehicles to travel at a speed of 30 kmph. Our main road has a single cross road at each signal. That’s three signals in all, plus the one at the start of the stretch.

Present situation

Each set of signal lights has a simple controller that decides when the lights for the main and cross roads will turn red, amber or green. The lights at each signal are independent of the others, and you get a red light for 1.5 minutes. After you leave signal 1, in the worst case you reach each signal just as it turns red.

Total travel time: 4.5 minutes to get past signal 4.

Here’s our new coordinated signal

To enable you to through all signals without stopping, each signal should turn green just as your vehicle reaches it. When you leave signal 1, you reach signal 2 after 0.5 minutes, signal 2 after 1 minute, etc. Which means signal 2, 3 and 4 should turn green 0.5, 1 and 1.5 minutes respectively after signal 1. To achieve this we just need a slightly more complex controlling system that is connected to all three signals and controls them according to pre-programmed logic.

Total travel time: 1.5 minutes.

We’ve increased the traffic speed three times without widening the road.

This is a simplified case, and actual conditions on the road are more complex. That’s why, although you and I designed this basic coordinated system with our knowledge of primary school maths, we need experts to design the more complex ones.

In modern coordinated signal systems, it is possible to travel long distances without encountering a red light. Traffic lights are centrally controlled by monitors or by computers to allow them to be coordinated in real time to deal with changing traffic patterns. Video cameras, or sensors buried in the pavement can be used to monitor traffic patterns across a city. The cost of such systems is a tiny fraction of the cost of road widening.

Option 2 – Underpasses or overbridges

We know what these are, and how they can help. Underpasses are of course preferable to overbridges in terms of aesthetics – there is no ugly concrete sticking up in the air.

Coordinated signals are the better solution, and must be used as the preferred option wherever possible. They require no extra construction and the resultant destruction of trees and buildings.

Then why are we destroying our city?

Sankey Road has now been widened. The stretch from the Windsor Manor bridge till Cauvery Circle remains unchanged, a two-lane road. When you come down from the Golf Club, at Windsor Manor the road is effecively single lane just before the bridge. If you drive down this stretch the next time you’ll see what I mean. The width of a road is actually the width at its narrowest part, so Sankey Road is effectively single lane.

A beautiful line of trees has been cut down on either side of the road, the High Point police station has been destroyed, the road has eaten into the golf course on one side and the properties on the other side. We’ve also similarly destroyed St. John’s Road in Koramangala and Bellary Road. All completely unnecessary.

The problem was not the road width, and the solution was not widening.

How come the city’s planners have not learnt from the Hosur Road experience?
How come you and I, who have no expertise in transportation engineering or town planning, can understand the Schumi-Bang effect but the people in charge of the city administration cannot ?
How come they never think of the intersections, and are hell bent on widening the roads?
How come they still cannot think beyond solutions like elevated roads going East-West, North-South and on Mysore Road, a repeat of the totally asinine elevated road to Electronic City ?
How come the ‘experts’ are thinking of increasing road space instead of improving the utilization of the existing road space?

BBMP now plans to widen 91 roads in the city, totalling 140 km. This is what the road widening is going to cost the city:
1. Homes are going to be destroyed
2. Businesses are going to be destroyed
3. Going by past experience, the new roads will not have footpaths.
4. Scores of footpath vendors are going to lose their livelihood
5. Pedestrians are going to be even more marginalized than they are now
6. Children, senior citizens and physically challenged people will be totally unable to use roads
7. A lot of beautiful old buildings are going to be destroyed
8. Approximately 40,000 trees are going to be cut
9. Bangalore’s temperature will rise even further because of the addition of heat-trapping concrete and tar.
10. We as taxpayers are going to pay the money for all this, we as residents are going to suffer the environmental consequences of all this.

BBMP’s 10-point programme!

Bangalore as we know it is going to be non-existent. There is going to be a spanking new Bangalore, ‘on par with international standards’ as our CM says. Soulless, devoid of history, devoid of trees, devoid of culture, designed for automobiles rather than for people is what sparkling new Bangalore will be in the near future.

Unless we think of solutions other than road widening? ⊕


These animations are highly simplified versions of actual roads, just to illustrate the concept.

See animation on Coordinated signals
See animation on Uncoordinated signals


  1. Interestingly, BBMP thinks the exact opposite. Within a 0.5km radius in Banashankari, 4 new signals have been installed. I notice this everywhere in Bangalore. Each time traffic increases a little bit, a new signal duly comes up. And of course, that marvel of urban planning near NIMHANS; a signal for pedestrians to cross the road instead of an overhead bridge. Arggghh is the best response one can offer.

    They should add a ‘Like’ button here.

  2. Great ideass.. maybe our city engineers and planners got their education through the “Dakshiney” route rather than pure merit and capabilities. Is that why we’re lurching from one incompetent solution to another endlessly?

  3. My response to Vinay’s comment:

    1. See the second para of the option suggesting underpasses. Grade separation for traffic is not the ideal solution within a city, but is definitely a better option than road widening.

    2. Where absolutely necessary, underpasses (in cities that are designed for people rather than vehicles) are built for pedestrians as much as for vehicles. Bangalore’s underpasses are a poor example to judge them.

    3. The ideal solution is roads crossing at grade, with pedestrian crossings at grade (not under the road or as skywalks).

    For this to be feasible, traffic population has to be brought down dramatically (maybe 25 % of what it is now?). This is only possible if the city adopts public transport wholesale. Public transport of course means the last mile transport too, so it means CyBaNa (Cycle + Bus + Nadiyodu).

  4. Very good article!
    I hope the “experts” realize that implementing proper traffic management systems (like synchronized signals and real-time traffic monitoring) is more effective than taking up adventurous road widening projects.

  5. Blame the planning woes on the City’s eternla traffic planning adviser, MN Srihari! Where’s was he when all this happened and what was he smoking?

  6. Das must be given rich credit for the new vocabs he creates. After the revolutionary CyBaNa, now Schumi-Bang effect! 🙂

    As Faiq says, spot on on the road-widening1 However, I’d like to differ with you on one of the solutions – under-passes. Under-passes or Making junctions signal-free causes vehciles to move continuously and with great speeds, making it difficult to cross roads. This is a bad soln for pedestrians, cyclists and for the differently abled. Of course you can say, we’ll build pedestrain under-passes too, but do they really work? how will the differently abled climb up and down? what abt old people? and what abt security in underpasses after dark? Read this report – BBMP admits the securiy issues and wants gurads for underpasses – ! Other than this issue mentioned, another point is they are just a temp solution to shift traffic to the next junction. Underpasses are a bad idea Das.

  7. Well said, someone commented that it is also like stitching bigger and bigger trousers when you get fatter and fatter, you are not fixing the problem really. The same is true for the umpteen dams on major rivers which is one of the reasons of the flood fury as well. Nobody bothers about the natural “flow” while designing roads and dams. They are screwing up the highways as well where they don’t really design the roads for the environment, but apply a blind philosophy of widening and separating traffic, forcing bullock carts and 2-wheelers go right against the traffic!

  8. Your maths is spot on!
    I had once challenged a friend (we live and work in same areas) that i can reach home on my cycle before he does on his mobike. Needless to say, i won. Thanks to the ‘Schumi-Bang effect’.

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