SELECTION OF SUITABLE TRAFFIC MODEL USING FUNDAMENTAL DIAGRAM UNDER DIFFERENT ROAD GEOMETRY AND OPERATING CONDITION IN MEKELLE CITY SUB-ARTERIAL ROADS

Abstract

The relationship between macroscopic traffic flow parameters (flow rate, speed, and density) is represented graphically by fundamental diagrams. These diagrams play an important role in traffic flow theory and transportation engineering. Most conventional traffic stream models are mainly applicable for homogenous traffic conditions. These models are not suitable for the traffic condition of Mekelle city which is characterized by weak lane discipline and heterogonous in nature. This thesis select suitable traffic model for different roadway geometry and operating condition. It also compares the flow parameters for the stated traffic condition. For this thesis three different cases have been considered, those are road way with and without median structure, road way with and without footpath and road way with and without side market. Traffic data collection is done through video recording at midblock rod from six different locations. To select the suitable traffic model the speed –density plot of field data for different locations is fitted with five established FD models linear, polynomial 2nd degree, polynomial 3rd degree, exponential and logarithmic. From the result, polynomial 3rd degree is the best FD model for case one which compares the roadway with and without a structural median. For the second case which comprises roadway with and without footpath, exponential models are the best-fitted model, but hence it doesn't satisfy the boundary condition to compare the flow parameters polynomial 2nd degree is the second best model. Similarly, for case three which compares roadway with and without side market the exponential and 3rd-degree polynomial is the best-fitted models, but hence exponential model doesn't satisfy the boundary condition to compare the flow parameters 2nd-degree polynomial is the second-best fitted model. It is also found that free-flow speed trends decrease if there is no structural median, footpath and if there is a road side activity by (4.8%, 6.19% and,9.11%). The jam density increases if there is no structural median, footpath and if there is a road side activity by (41%, 8.8% and, 6.68%) consecutively.