Travel demand assessment in GIS

Travel demand assessment in GIS

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Abstract
R.S. Moorthy
Sr.Transportation Engineer
T&C Department, CIDCO, CBD-Belapur, Navi Mumbai ,India-400 614
Tel:+.91-22-7918630, Fax:+91-22-7918100, E-mail: [email protected]

Prof. S.L. Dhingra
Professor, Dept.of Civil Engg.
Indian Institute of Technology, Powai, Mumbai India-400076
Tel:+91-22-5767329, Fax:+91-22-5767302, E-mail: [email protected]

Prof K.V.Krishna Rao
Asso. Professor,
Dept.of Civil Engg., Indian Institute of Technology, Powai, Mumbai 400 076
Tel:+91-22- 5767305, Fax:+91-22-5767302, E-mail: [email protected]

Abstract
Cities are dynamic in nature. They undergo several changes due to economic, political and technological changes. Development plans prepared for cities are not remain rigid; they need to be periodically reviewed, and up-dated to suit the contemporary requirements and future needs.

Thane city is one of the fast growing municipal areas of Maharashtra State. The city with geographical coverage of 128 sq. km required a new look at it`s intra -city public transportation system to meet the growing demand. In order to assess the requirement and identify a suitable transport system a scientific study through an efficient technology was felt necessary . Since the transportation systems have a strong geographical link, the database on GIS platform was found suitable for transportation planning.

The important phase of transportation planning is “assessment of travel demand”. Since demand is the basis for i) identification of suitable technology, ii)working out the supply requirement and also iii)deriving various other components such as financial feasibility , system sustainability etc. emphasis is given in this work to assess the travel demand .

Travel demand models are used to predict changes in travel and utilization of the transportation system in response to changes in land-use, demographics, socio-economic conditions . In the conventional transportation planning process, data collection is a major part of the work and converting them from different scales to the required scale is a time consuming process. The available data are in paper format with different departments and organisations ; and, most of the times they do not meet the requirements due to variations in format. This problem is prevalent in most of the organisations. Geographical Information System (GIS) is a preferred platform , because the data attributes are associated with topological object (point, line or polygon) . In GIS, informations are identified according to their actual locations. The graphical display capabilities allow visualization of different locations of traffic generators, network and routes. The use of GIS in transportation planning will enhance the visualisation aspect and facilitate the development of decision modules for use by the transport planners.

The objective of the study was to develop GIS data base for an integrated and multi-modal transportation system and network for an urban area and enabling the platform to perform travel demand models. The scope of work includes development of GIS data-base with all the required attributes , development of models and fore-casting the travel demand for various transportation system for various land-use, alignment and policy scenarios.

The GIS database was established by updating the Survey of India topo-sheets on 1:25000 through municipal ward maps and structure plan of Thane and, satellite imageries (PAN+LISS-III merged-March,2001) of National Remote Sensing Agency (NRSA), India. The digital maps of , traffic zones, transportation network were generated in GIS environment. The maps thus created were transformed in to Transportation -GIS by attaching the appropriate attributes . The information regarding socio-economic, demographic and traffic and transportation parameters were well structured, linked with geographical entities for making queries, carrying out analysis and performing modeling exercise.

The main part of the study reported in this paper is assessment of the travel demand for the various transportation system under different scenarios in GIS environment. This demand was estimated for the horizon year (2031) and the phasings are for every 5 years. Development, calibration and validation of suitable demand models were the important and critical tasks. The four stage UTP model was performed in GIS environment using Trans CAD-a GIS software . Multiple linear regression technique for Trip Generation (TG), Gravity model for Trip Distribution (TD), Multinomial logit Model for Modal Split (MS) and User Equilibrium Model for both Highway and Public Transport Assignment (TA) were used in this study to assess the intra- city travel demand. Appropriate growth factor models were established for assessment of external trips.

After calibration process, the models were validated with base year data. The validation process revealed a closer comparison of the observed value and model value. The modes thus developed were used to predict the travel demand for various developmental and policy scenarios, including Mass Rapid Transit System (MRTS). It was observed that TG-TD-MS-TA interaction, desire line diagram ,flow volume, V/C ratio, model-observed value comparison etc became very easier and efficient because of the visualisation facilities such as scaled symbol themes, charts, color pattern themes etc provided in Trans CAD.

The GIS enabled the entire process of UTP modeling exercise through Trans CAD in a most efficient manner. Besides, the system greatly helped in decision making process as a decision support system to test various developmental and policy scenarios in order to arrive an optional transportation requirement.