The urban traffic networks of cities are complex with many transport modes that share and compete for limited road space in the urban landscape. As part of An Accessible City (ACC) framework of Christchurch that was established in 2013, the Manchester Street upgrade project has been recently completed to improve accessibility in and around Christchurch CBD across a range of transport modes. New road layout and space allocation have been introduced in the network including a Bus Priority System (BPS) along the route. In collaboration with Christchurch City Council (CCC), Christchurch Transport Operations Centre (CTOC), and Environment Canterbury (ECAN), this research paper studies the performance of the network and multi-modal traffic dynamics of Christchurch Central Business District (CBD) using Aimsun, a microscopic traffic simulation program. The urban network of Christchurch CBD was modelled in Aimsun using the latest GIS map from Environment Canterbury. The traffic demand of the CBD during the peak morning period (7-9 AM) was generated using the latest Origin-Destination (O-D) matrix from the 2018 Christchurch Assignment and Simulation Traffic (CAST) model in SATURN program. 119 signalised intersections in the CBD were implemented in the Aimsun model using fixed signal phases that are based on the Sydney Coordinated Adaptive Traffic System (SCATS) of Christchurch. All existing bus routes and bus stops within the CBD have been implemented into the Aimsun simulation with the latest bus information from Metro bus company. Two simulation scenarios were explored in Aimsun to investigate the effects of BPS in the CBD network. The results show that the effects of BPS in the performance of the multi-modal traffic dynamics of Christchurch CBD are minimal. However, it is noted that the results are of the entire CBD network and the effects of BPS should be further investigated at the local scale to validate the results.