Median openings are one of road features in urban road which are left intentionally for U-turn movement and their role play an important part on improving the capacity of the road specially the minor traffic stream. So that the study of U-turn movement at median opening is significant for different purpose. Critical gap is one the major parameter that plays main role in the study of the behavior of the median Opening and their effect on the major traffic stream. Different critical gap estimation methods and models has been provided in the past by different researchers at different countries for different type of traffic system. Among those methods Modified Raff, Asheworth, Harder’s, Maximum Likelihood, Probability Equilibrium and Modified INAFOGA method are the most common one. However, modified INAFOGA method is the recommended one for the traffic, which is mixed, and lane discipline is violated. This method follows the merging behavior approach that is the critical gap value is estimated from the graph in which the cumulative distribution of merging time, which the U-turning Vehicle needs to traverse the INAFOGA and the Accepted gap, is plotted and the intersection of those two graph will be taken as the critical gap. In this study, the data was collected using the video recording technique (16MP camera) at different selected median openings, which are Mebrat Hayil, on the road from Gamby roundabout to begitera and around Lemilemitu during peak and off-peak period of the day. The data collected was played using computer for the extraction of the necessary variable. The extraction of the necessary variable is done by using the stopwatch software. The final result showed that three wheeler vehicles registered a minimum critical gap of 3.3sec and a maximum of 4.4 sec and also passenger cars has shown that a minimum of 4sec and a maximum of 6.38sec. At the same time, mini-bus has a minimum of 4.37sec and a maximum of 5.82 sec. For three wheeler, waiting time has a negative exponential relationship with the critical gap and a negative linear relationship with the conflicting traffic flow. Passenger cars and minibus has a negative power relationship with both waiting time and conflicting traffic flow