Circulación vs. tráfico vs. tránsito
The words 'circulación', 'tráfico', and 'tránsito' in Spanish can all be translated as 'traffic' in English. However, there are nuances in their usage that may reflect different aspects of traffic.
Circulación
'Circulación' refers to the movement or flow of vehicles or people in general, it is often used in conjunction with road conditions and traffic rules.
La circulación está interrumpida por la manifestación.
(The traffic is interrupted because of the demonstration.)
La circulación en las autopistas es fluida.
(The traffic on the highways is smooth.)
Tráfico
'Tráfico' generally refers to the density or accumulation of vehicles in an area, often relating to congestion.
Hay mucho tráfico en la hora punta.
(There is a lot of traffic during rush hour.)
El tráfico en las calles es pesado debido al accidente.
(The traffic in the streets is heavy due to the accident.)
Tránsito
'Tránsito' is more formal and often used in official contexts regards to transportation and mobility, it can also refer to short-stay transit in general.
Las normas de tránsito deben ser cumplidas.
(Transit rules must be followed.)
Estoy en tránsito en el aeropuerto.
(I'm in transit at the airport.)
Summary
While 'circulación', 'tráfico', and 'tránsito' all indicate movement or flow, 'circulación' broadly discusses the general state of movement, 'tráfico' translates more directly to traffic or congestion specifically on roads, and 'tránsito' represents a more formal and broader term used often used for transit rules or systems.