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Lanes, Are They Useful?

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Written By tsubba - 2 August, 2007

Traffic Bangalore lanes BTRAC Analysis

Can lane discipline really reduce traffic jams? Are lanes of any use? Given how things are, not as they are designed, and not unless they put some thought to it.

Real use of lanes is not to control flow in midblock sections. Providing lateral or sideways safety buffers, and segregation of flow that is changing directions are much more important reasons why lanes are required. The real value of lanes is at intersections where by proper partitioning, turning traffic can be segregated. Lanes can thus release a lot of the pressure at intersections. But lanes at intersections cannot work without lanes midblock. So lets discuss midblock lanes.

Look at Mark Pritchard's image in the right. On the road going south, strict laning( 3mtrs/lane IRC standards) would enforce exactly two lanes. But, in natural, unenforced flow, people are making much more efficient use of the road. From the image it is clear that non bus traffic can quite conveniently use 3 lanes, while buses can safely use only 2 lanes.

More cars, autos and two wheelers and cycles use the roads than buses. Designing the lanes from bus' perspective results in non optimal usage of the road. If people lined up one behind the other in two lanes, the jam would have been at least 50% longer!!

So two lane design, which is based on standards, will fail because nobody will follow it, and even if they followed it, two lane design would unnecessarily spread congestion.

But not marking lanes is not the answer. No lane marking would result in > 3 lane traffic which is dangerous because side separation between vehicles is then reduced*. So there has to be some design to enforce discipline.

What is it? Are smaller lanes the way to go? Would three lanes design - allowing only the buses to straddle two lanes work? What do you think?

[*During my days of idealism, I used to rent cycles. One day, an auto came so close to me that the right pedal of my cycle got stuck in the auto. Got wounded, had to pay 50 rs extra to the rental guy.]

COMMENTS

we create our own rules ...

silkboard - 2 August, 2007 - 14:32

... around these lanes? Drivers in our country form chaotic yet self organizing groups. Low speeds in the city, not enough space - make as efficient use of road width as possible (Tarle's picture and explanation above). A faster highway - better use those lane markers (a pic I took on Pune expressway - I noticed guys have learnt to stick to lanes)

City Roads Need Their Own Standards.

tsubba - 2 August, 2007 - 15:21

Highways outside city limits are a different beast. The speeds are higher and hence lateral buffers need to be wider for safety. Moreover, the volumes are lower. Not city roads and highways within city limits.

If traffic self organizes in such a way that the design is being consistently violated, then what should be done? Where is the problem?

Is this showing that the design is flawed? Is it chaotic because you are trying to impose the wrong structure? Are you trying to solve the wrong problem with the wrong solution?

Some more illustrations:

* Joe Arnold (very instructive)

* MN Vasu (gorgeous pic) 

Uneven lanes?

shas3n - 2 August, 2007 - 17:26

I might be taking a really vague shot here, but how about uneven lane widths? Left lane the widest and for the buses, the middle one about 2.5m (or less) for cars and the right most for bikes/autos who would anyway be comfortable at the fast lane.

In other countries the traffic is more or less homogenous so an equal lane width would work. In India the traffic is as diverse as population. We need something really specific to our needs I guess.

I heard driving in Italy, Mexico etc is equally bad and its no coincidence that they have fairly divere traffic too.

-Shastri

mixing objectives

tsubba - 2 August, 2007 - 19:37

segregating vehicles by type will work as long you are midblock, the moment you hit an intersection it is chaos. how will buses on the left lane turn right? and how will cars on the left turn left? you will have to work on signals then. separate signals for each type and direction. green for left lane, separate for others turning left, separate for others turning right...

more later... have to run

Some points about lane

Visitor - 3 August, 2007 - 05:00

Some points about lane system followed in the US 1) in the US, all the vehicles move at a constant speed on the roads ( more or less equal). They stick to the upper and lower speed limits. (not the case in india, where you have bullock carts to ferraris on the same road) 2) Not only are the lanes segregated, at every intersection, there are separate lanes (new ones, the road widens)for people who want to turn. So if you continue on the road, you get your own lane. If you are turning you move to separate lane reserved for turning and wait. And there are marked entry areas to these turning lanes. if you miss that, good luck, go to the next U turn. ( not the case in india, our roads are of uniform width, whether near intersection or not) 3) the roads are designed to carry that much traffic. (Our roads carry 10 times of the traffic they are designed to carry) Basically we have an unplanned road system which is evolving ( rather very late) to the demands. Hence all this confusion about lane system. This is why we have authorities who do not strictly enforce lane system, they know that the system will not work in current scenarios and no point in enforcing it right now. "But not marking lanes is not the answer. No lane marking would result in > 3 lane traffic which is dangerous because side separation between vehicles is then reduced*. So there has to be some design to enforce discipline". It is >3 lane traffic in most roads in bangalore. For this to change two things should happen 1) Better infrastructure 2) Better discipline among people. both go hand in hand.

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