Browsing by Author "Birhanu, Girma(PhD)"

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    Logit Model of Work Trip Mode Choice for Bole Sub- City Residents
    (Addis Ababa University, 2007-02) Teshome, Mekdim; Birhanu, Girma(PhD)
    The issue of mode choice is probably the single most important element in transport planning and policy making. It affects the general efficiency with which we can travel in urban areas, the amount of urban space devoted to transport functions, and whether a range of choices is available to travelers (Juan De Dios Ortuzar, Luis G. Willumsen, 2004). There are two transport studies undertaken for Addis Ababa which are part of the development and revision efforts of the Addis Ababa master plan. In both studies, the four stage travel demand model was adopted. However, the mode choice models developed in both studies are direct demand models which are basically based on aggregate data. However, with present knowledge and computer technology, it is possible to model the mode choice for more than two alternatives by considering both the travel maker’s and the travel mode’s characteristics. Moreover, considering both socio-economic and travel mode variables will lead to a better understanding and simulation of the people’s behavior in choosing among the competing modes. Therefore, in this research a Multinomial Logit model is developed, which is based on disaggregate socio economic, mode and trip related data, for work purpose trips made by Bole Sub-City residents. The different modes of road passenger transport considered in the model are Walking, Small Taxis, Mini-Buses, Anbessa City Bus, Lonchina, Private vehicle as driver, Private vehicle as passenger and Company provided transport. Among the various methods of revealed preference surveys, Household or Home Interview Survey was used as a data source in addition to secondary data obtained from different agencies of the city and this has been exploited to create the level of service data for the competing modes. Finally different specifications of multinomial Logit models have been tested and it has been observed that the mode choice model has shown continuous improvement as explanatory power as it was enhanced from being restricted to mode related variables to incorporating the socio economic and trip related variables.
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    Methodology for Traffic Safety Audit and Inspection of Bridges
    (Addis Ababa University, 2011-09) Eshetu, Tegegne; Birhanu, Girma(PhD)
    Bridges are structures including supports erected over a depression or an obstruction for carrying traffic and other moving loads. They are crucial elements of the road design elements and transportation infrastructure. There are around 3,100 bridges registered in Ethiopia in Bridge Management System. Although a considerable research has been carried out on Traffic safety on highways and Road Safety Audit as a whole, very little work has been done on traffic safety Audit and Inspection of bridges. Most of the inspections of bridges concentrate on the structural defects of bridges leaving the safety aspect of the bridge and approach roadway as a secondary concern. Bridges and bridge approaches have been identified as one of the leading locations for severe, single-vehicle crashes. There are many bridges and culverts on the highway system in different parts of Ethiopia. Most of the bridges have rigid rails and often span a potentially hazardous feature. This thesis presented a methodology for traffic safety audit and inspection of bridges. Checklists were prepared for each stage of design starting from planning stage through construction stage so that safety elements aren’t overlooked by the designer. The checklist incorporates important safety features to be checked such as, the adequacy of bridge width, the adequacy of pedestrian width, the application of constant width for the approach roadway as well as bridge, adverse geometric alignment at the bridge approach roadways, and the incorporation of crashworthy transitions, approach guardrail and end treatments. Sample projects which are found at different stages of design were selected for an implementation exercise. As part of this thesis, bridge safety inspection sheet was developed for the safety inspection of existing bridges. It was assumed that the results will create awareness to most bridge engineers who deal with the structural assessment of existing bridges. Bridges located on Modjo – Awassa road were used for developing the bridge safety inspection sheets. None of these bridges has end treatments, approach guardrail and transition section. The major defects noted include, cross section constriction, poor approach alignment, sight distance constraints and high fill heights without safety barrier on the approaches. Inspection procedures and data sheets are prepared based on intensive literature review and field inspection of existing bridges. Bridge engineers and inspectors are advised to use the developed safety inspection sheet as part of their routine structural inspection of existing bridges.