Which concept tests the speed of traffic when density is zero?

Which concept tests the speed of traffic when density is zero?

• A. Bottleneck
• B. Transit-Oriented Development
• C. Free-Flow Speed
• D. NEPA

Answer: (C)

Free-flow speed is the speed cars would travel when there are no interactions with other vehicles, i.e., at very low density. In traffic flow theory, as density approaches zero, the observed speed approaches the free-flow speed, representing the road’s upper limit under light or no-traffic conditions. It reflects the speed drivers choose when not impeded by others, often aligning with the posted speed limit or typical travel speeds in uncongested conditions. The other ideas point to different concepts—bottlenecks relate to capacity reductions and congestion, Transit-Oriented Development focuses on land-use planning near transit, and NEPA concerns environmental impact reviews—so they don’t describe how speed behaves when density is essentially absent.

Free-flow speed is the speed cars would travel when there are no interactions with other vehicles, i.e., at very low density. In traffic flow theory, as density approaches zero, the observed speed approaches the free-flow speed, representing the road’s upper limit under light or no-traffic conditions. It reflects the speed drivers choose when not impeded by others, often aligning with the posted speed limit or typical travel speeds in uncongested conditions. The other ideas point to different concepts—bottlenecks relate to capacity reductions and congestion, Transit-Oriented Development focuses on land-use planning near transit, and NEPA concerns environmental impact reviews—so they don’t describe how speed behaves when density is essentially absent.