Research
Empirical Methods of Capacity Estimation of Urban Roads
Determination of road capacity is a major issue for transport planners. Capacity is defined as the maximum number of vehicles that can be accommodated per unit time under given condition of occurrence. Capacity studies for heterogeneous traffic situations are very complex and only limited studies undertaken. Here again there are several methods of estimation of capacity. However the major types of estimation can be classified under two broad categories as Direct Empirical Methods and Indirect Empirical (Simulation) Methods. Because of the complexity of the heterogeneous, high volume traffic on Indian urban roads, it is appropriate to model the flow parameters and adapt direct empirical methods for estimation of capacity. In this paper an attempt is made to study the fundamental details of traffic flow and evaluate the capacity of urban mid block section, particularly for a two lane divided cross section. The traffic data at ten locations in Chennai city was collected through video graphic survey. Detailed extraction of traffic headway (inter arrival time), volume and speed were made for every 5 minute time interval, covering both the peak and non peak period. Using the fundamental parameters, capacities of sections were evaluated by three methods, namely Headway method, Observed volume method and Fundamental diagram method. Detailed analysis of the arrival pattern of vehicles was made and appropriate distribution identified to get the mean headway. The Selected Maxima method assumes that the capacity state is reached during the survey period. As against the normal time slice of 15 minutes, a 5 minute time slice was considered for identifying the peak flow rate. In the third approach, a plot was made between traffic flow in PCU and the speed, to compare the relationship. Since the data was scattered, the enveloping curve technique was adopted, even though the usual pattern of speed flow curve is parabolic. The average capacity of a standardized two lane 7m) urban mid
Systems Dynamics Simulation Modeling of Transit Oriented Land use Development of a Rail Corridor in Chennai
The growing concern of rapid increase in urban population and vehicular growth culminates into emerging of many metropolitan cities. In such areas, spatial distribution of activities warrant, the necessity for travel by appropriate arrangement of sub-systems in tune with the form of urban structure and routes serving it. In Chennai, the present modal split revealed that only 40% of the travel in the City is made by public transport as against a minimum of 70% recommended by the study group or alternative systems of urban transport system. The modal split between bus and train will have to change from 88:12 (2004) to 60:40 (2026). It calls for a strategy reorienting the travel by appropriately manipulating the policies so as to increase the share of Public Transport. Hence, there is an urgent need to study the land use transport interaction along the suburban rail corridor to increase patronage. The northern region suburban railway line of Chennai Metropolitan Area is taken as the study from Chennai Central to Gummidipoondi. An opinion survey has been conducted during morning and evening peak period to know the opinion of the train passenger, mode used and distance traveled from origin to station and station to destination was collected. It is found that the majority of originating points are within 2.50km from the station locations. Hence, in this study an attempt is made to find the trend of land use disposition in various periods. Land use map prepared by digital image processing methods using ERDAS Imagine 8.7 software, panchromatic aerial photograph, IRS1D, IRS P6 LISS III Digital data. As the assessment of patronage along the corridor involves a large number of complex and dynamic variables suitable simulation software, namely a dynamic package called STELLA is used to develop the model and test the same for various simulations. Application of this model to similar urban area with moderate modifications will prove to be valid. Further, the model can also be ext
