Abstract:
A transport modelling system has heen developed in this study to forecast
traffic flow-pattern and traffic volume on the national highway network of
Bangladesh. The model and the descrihed procedure are intended to provide
highway planners with a tool for simple, fast and inexpensive estimation of
traffic projections.
This study attempts to comhine the transport models of trip distrihution and
traffic assignment for forecasting traffic flow-pattern between old 20 districts
and volume on the national highway network of Bangladesh. A douhly
constrained gravity model of trip distribution and a capacity restraint traffic
assignment model have heen computerized for this purpose. It is assumed
that, the shortest path will be selected on the basis of minimum travel time
and minimum travel cost for passenger and freight movements respectively.
The gravity model is calibrated with the hase year (1990) data and the results
of calibration are used to formulate regression equation of power form
between travel resistance and the resistance variables lime and cost. The
results of regression show that, the exponent for time is 2.05 with a
correlation coefficient (r) of 0;98 and the exponent of cost is 1.76 with a
correlation coefficient of 0.83. These higb values of correlation coefficient
indicate that, the gravity model developed in this study can he used for
reliable forecasting of traffic flow-pattern between old 20 districts of
Bangladesh.
The traffic assignment model has heen applied for forecasting traffic volume
on the national highway network of Bangladesh. Growth rate of traffic for
passenger and freight movements have heen calculated for all the 20 districts
of Bangladesh assuming that, traffic growth rate is a function of some
economic and demographic factors. Traffic volume on the road sections of
the national highway network of Bangladesh has been projected for 20 years
(1990-2010) at an interval of 5 years under existing condition of the network.
The model has ,also heen applied to forecast traffic volume over Jamuna
hridge in 1997 which is assumed to he'the opening year of the Jamuna hridge.
To assess the validity of Forecasting, traffic volume over the Jamuna hridge
in 1994 from this study and in the Jamuna hridge study have he en compared.
This comparison shows a variation of only 5.5% for total' traffic (passenger
and freight) between the predictions made in these two studies. The results
also show that, due to the construction of the Jamuna hridge one of the
heavily loaded Dhaka- Aricha highway will lose more than half of its traffic
in 1997.
