Abstract:
The most common approach to modelling in Sri Lanka is based on zoning of the
area concerned, and the identification of the travel network within the area,
connecting the different zones. The resulting travel patterns of bus and rail are
understood as an inter-zonal travel made between the different zones.
The set of models used for transportation planning in the Colombo Metropolitan
Region has inconsistent structural forms with the formulation of different types
of variables. Most of these variables are not common to each other. As a
consequence the model estimation requires a large data base. Pertaining to this,
a set of bus and rail passenger demand model forms is calibrated to a common
modelling format, on a scientific basis.
These models attempt to explain (a) bus travel demand, (b) rail travel demand
using season tickets,(c) rail travel demand using ordinary tickets and (d) total
bus and rail travel demand. In these models, the impedance to travel is
expressed in a generalized form, which includes travel fare, waiting time,
transfer time and travel time. The product of employee population and the
housing density between zones are the best fitted variables which explain the
travel characteristics of the region.
The Mode choice modelling is one of the most crucial parts of travel demand
modelling. With regards to this, the sound theoretical approach to the modelling
facilitates the better understanding of traveller behaviour in the mode choice
process. The theoretical framework of the bus and rail choice model has been
formulated using logit theory, energy theory and economic theory. The variables
fitted in this model are expressed by time variables such as, the utility
difference between passengers (a) walking time to the mode, (b) in-vehicle travel
times of bus and rail and (c) the loss of traveller comfort due to the loading
levels and waiting time of the modes. The inclusion of bus and rail loading
factors in the model, is important and has a great ability to represent the
traveller characteristics of the inter-zonal travel. Therefore, the model can be
applied for transportation planning studies not only to the study area but also
to any Metropolitan region in the developing countries, which is of a similar
nature in the travel characteristics.
The statistical tests reveal that the set of demand models for bus, rail and total
public transportation has been successfully calibrated. It indicates the variation
of the coefficient of correlation is between 70% and 80%. In fact, the choice
model indicates this value is 85%, and 0.289 of the log likelihood index, which
makes one conclude that the theoretical choice model has an acceptable fit, of
the variables and the data.
