page_title: Traffic flow
section_title: Density
hierarchical_section_title: Traffic flow / Traffic stream properties / Density
caption_attribution_description: English: Traffic flow time-space diagram showing areas for analyzing k and q.
context_page_description: In mathematics and transportation engineering, traffic flow is the study of interactions between travellers and infrastructure, with the aim of understanding and developing an optimal transport network with efficient movement of traffic and minimal traffic congestion problems.
context_section_description: Density (k) is defined as the number of vehicles per unit length of the roadway. In traffic flow, the two most important densities are the critical density (kc) and jam density (kⱼ). The maximum density achievable under free flow is kc, while kⱼ is the maximum density achieved under congestion. In general, jam density is seven times the critical density. Inverse of density is spacing (s), which is the center-to-center distance between two vehicles.
       
  The density (k) within a length of roadway (L) at a given time (t₁) is equal to the inverse of the average spacing of the n vehicles.
       
  In a time-space diagram, the density may be evaluated in the region A.
       
  where tt is the total travel time in A.
caption: Figure 5.
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