Traffic evaporation
2022-11-12 → 2026-10-26
What is traffic evaporation?#
Traffic evaporation describes the reduction in motor-vehicle trips that can follow a road closure or reallocation of road space. Some drivers use another route, but others change when, where, or how they travel or do not make the trip.
Open Plans’ short video explainer describes the idea.
Is it real?#
A review of more than 70 cases across 11 countries found that congestion was rarely as bad as pre-project predictions (which tend to be “excessively pessimistic”): on average, 21.9% of the vehicles previously using the treated road or area (median 10.6%) could not be found anywhere in the surrounding area afterward. The traffic disappeared rather than diverting to nearby streets.
Cases#
Cheonggyecheon#
Seoul removed 5.8 kilometers of elevated highway and four of eight surface lanes to restore Cheonggyecheon. OECD’s review of before-and-after monitoring found that most of the former traffic did not reappear on adjacent streets or elsewhere in the urban area. The principal responses were shifted departure times and a significant increase in Metro use.
Pontevedra#
The city of Pontevedra saw a ~90% drop in car traffic after pedestrianizing its historic center.
Barcelona#
Nello-Deakin (2022) studies the case of Tactical urbanism in Barcelona: traffic on 11 intervention streets fell 14.8% relative to the rest of the city while immediately adjacent parallel streets gained only 0.7%, meaning most of the displaced traffic evaporated rather than diverting.