PT Journal AU Zewdie, R Hora, J Nigussie, Y TI Circular Colouring for Emission Minimalization SO Transactions on Transport Sciences PY 2013 BP 159 EP 168 VL 6 IS 4 DI 10.2478/v10158-012-0043-y DE Circular colouring; traffic flow; circular chromatic number. AB The standard time allocation of classic road junctions in major towns and cities are often the main indicators of the government policy and management strategy in reducing traffic jams with its associated emission production from the traffic flow. In this paper, we apply the circular colouring method of Graph Theory (Vince, 1988; Zhu, 2001), to the emission reduction problem at a traffic road junction. The result of this paper is addressing this problem by optimizing the waiting time interval for two selected models. A traffic road junction is modelled as a finite graph G = (V, E). Each vertex v of G represents a given traffic light. Two vertices v and u are connected with an edge if their corresponding represented traffic flows collide and each time in such case they are given an overlapping green light time interval. ER