WE WOULD LOVE
Our content is
a public service!
IBF is 100%
Follow us on Twitter
Case Study New Dehli, India
By Geetam Tiwari and David Mozer
Street traffic in many cities, especially in less-Westernized countries, is often
characterized by a diverse mix of heterogeneous vehicles (including bicycles, cargo
tricycles and human and animal drawn carts). Generally all the modes find themselves in
the same one, two or three lanes albeit with a near infinite variety of traffic mix, flows
and densities at different locations and at different times. But there is another
similarity; this traffic is characterized by lack of any effective channelization (even if
lane stripes are present), mode segregation or control of speed (even if signed). In the
mind of the formally trained traffic planner it is anarchy! The prognostication would be
for some condition like total gridlock or total mayhem. Yet the people and goods keep
getting through. And may, by some measures, actually be doing it better than in controlled
conditions. And contrary to the conventional (traffic engineer) wisdom it is not anarchy.
These relatively unconstrained environments provide an opportunity to view traffic
behavior in a "natural" condition (though some "socialization" may be
playing a role.) Taking it one step further, by studying flow and safety characteristics
of motor vehicle (MV) and non-motor vehicle (NMV) behavior on these roads we get some
interesting insights into road use behavior in a situation of self-optimization.
A team from the Indian Institute of Technology, studied traffic flow and accident data
for MVs and NMVs at sixteen selected mid-block sites around New Delhi. The selection
criteria was designed to obtain a wide variety of traffic densities and modal mix. None of
the sites had physically segregated bicycle lanes. Collection of data on speed, flow rate,
densities and conflicts, was for all modes at each location. Video film was used in this
analysis. Crash data was collected from the police department.
Among the observations of the study are:
- NMVs and slow moving vehicles did not move in files and had a lot of lateral as well as
forward movements. The slower the general traffic speed the greater the in-filling by
NMVs. This was maximized at stops. Hence, for NMVs, flow/density measures typically
applied to MVs cannot be used. To get a more accurate assessment a geometrical based
measure of "aerial density" needs to be used. This definition takes into
consideration not only the varying degrees of freedom of the different modes but also the
varying size. Bicycles use the inside lanes only when setting up to make turns.
Integration only occurs when flow rates exceed saturation rate per lane; 6000 bicycles per
hour per lane, or 2000 passenger car units per lane per hour. At least at slow speeds and
initial volumes, bicyclists moving into the second lane do not seem to have a negative
impact on MV flows -- the bicyclists fit into the cracks -- actually increasing the
- The average speed of MVs at peak hours is much lower than the capacity speeds, but even
then the bicyclists are moving at their desired speed. At peak hours the average speed of
MVs doesn't vary much between high density and low density sites. MVs don't top the
saturation capacity in terms of passenger-car-units-per-hour in most three lane sites but
they are near capacity at some of the two and one lane sites. The bicycles at all sites
are well below the saturation capacity level.
- On two and three lane roads, as general traffic speed increases, bicycles primarily use
the curb-lane-zone (CLZ) and motor vehicles do not use the CLZ even when bicycle density
is low -- a defacto segregation develops. The CLZ is in fact a curb-lane-bike-zone. As the
volume of bikes increases the width of curb-lane-bicycle-zone increases. Hence, the
"critical mass" of bicycle use creates a defacto bike lane. The exception to
this defacto segregation is buses which move into the CLZ to discharge and pick-up
passengers. This creates many conflicts. (When the CLZ becomes too dense with bicycles,
the buses stop in the middle of the street, which creates another set of problems as
pedestrians cross the very active CLZ. Ironically, even where the engineers do not
accommodate NVMs, when speeds and volumes are right, traffic behavior suggests hat
segregated facilities for MV and NMV would be well received.
- On one lane roads (3.5 m wide), the bicyclists occupy the edge of the lane -- sharing
the lane with MVs. On these facilities both modes negatively impact on the maximum flow of
the other mode by over 60%. Again suggesting a benefit, at least in terms of flow, for
installation of a bicycle facility.
- Analysis of accident patterns show that the self-segregation of the modes is not
sufficient to ensure the safety of vulnerable bicyclists. While mid-block over-taking and
side-swiping accidents are not usually a serious consideration in regimented traffic
conditions, this category of accident dominates the statistics in New Delhi. Despite the
proximity of MV and MNV traffic, fatalities are low, but hardly negligible. The overall
statistics for bicycle fatalities in New Delhi show that 60% of bicycle fatalities occur
off-peak, when traffic volumes are lower, but MV speeds are higher. 40% of the fatal
bicycle accidents are during seven peak hours when volumes are significantly higher and
speeds are lower (20 to 30 km/h, 12 to 18 mph). (A breakdown of peak/non-peak volume is
not given.) Of the peak hour bicycle fatalities, 62% involve collisions with buses or
trucks. And, of all bicycle fatalities, 73% occur at mid-block. Again this is very
different from the statistic for high channelized Western cities.
- In the situations studied, the primary justification for separating MV and NMV is
safety, not capacity!
For information on the studies supporting this article, contact: Geetam Tiwari, Ph.D.,
Sr. Scientific Officer, Applied Systems Research Prog., Indian Inst. of Tech., Hauz Khas,
New Dehli, 110016. Fax: 91-11-685-8703. Email: [email protected].
Related article: Collision
course driving in the third world, by Fred Peace, New Scientist Magazine.
| About Us |
Contact Us | Contributions | Economics |
Education | Encouragement |
Engineering | Environment |
Bibliography | Essay Contest |
Ibike Tours | Library |
Links | Site Map |
The International Bicycle Fund is an independent, non-profit
organization. Its primary purpose is to promote bicycle transportation. Most IBF projects
and activities fall into one of four categories: planning and engineering, safety
education, economic development assistance and promoting international understanding.
IBF's objective is to create a sustainable, people-friendly environment by creating
opportunities of the highest practicable quality for bicycle transportation. IBF is funded
by private donation. Contributions are always welcome and are U.S. tax-deductible to the
extent allowed by law.
Please write if you have questions, comment, criticism, praise or
additional information for us, to report bad links, or if you would like to be
added to IBF's mailing list. (Also let us know how you found this site.)
DreamHost - earth friendly web hosting"
Created by David Mozer.
Copyright ? 1995-2016 International Bicycle Fund. All rights reserved.