The design of sidewalks in crowded areas is the great importance in cities. These spaces have more sensitivity if they are in the central business district (CBD). In this research, the main objective is to study, analyze and design the sidewalk adjacent to the bazaar in Semnan, Iran, with a CBD, located in the valuable historical context of the city. After surveying the pedestrian volumes during the peak hours in the morning and evening, the mentioned street was divided into eight parts, and the most traffic flow was considered as a criterion for the design. Then, based on HCM2016, the density and the Level of Service (LOS) of each part were obtained. Findings indicated that Part 4 had LOS E and density 11<11,52<18, Part 6 had LOS E and density 11<12,06<18 and also Part 7 with the highest traffic volume about 2500 people and the LOS E was prioritized to increase LOS. The data obtained for each part was studied by Pathfinder software and compared with the obtained manual information. Therefore, the road diet theory was implemented and with increasing the width of sidewalk about 3 to 5 feet per section, it caused to improving LOS.