The accomplishment of traffic engineering relies on the coordination among the stated three essential components that is the vehicles, the highways, and the street clients. This chapter explores the factors like human, vehicle, and road that influence transportation. The transportation engineer ought to deal with a collection of street client qualities. The human qualities like capability to respond to a circumstance, vision and hearing, and other physical and mental variables change from individual to individual and rely upon age, fatigue, nature of improvement, nearness of medications/liquor, and so forth. Traffic flow is the investigation of the movement of individual drivers and vehicles between two points and the connections they make with each other. The traffic stream incorporates a blend of driver and automobile conduct. Traffic control gadget is moderately utilized for imparting connection among traffic engineer and street clients.