Which traffic feature slows traffic while increasing efficiency?

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A roundabout manages speed and flow by forcing drivers to yield into a circulating lane and navigate at a low, steady speed. This design reduces severe crashes and keeps traffic moving overall, because vehicles don’t stop and start as often as at signalized intersections, so delays are minimized while throughput improves. The slower speeds inside the circle create safer interactions, yet the continuous flow reduces total travel time and fuel use compared with stop-and-go patterns. A chicane, while it slows vehicles, disrupts throughput with weaving and added delays, not improving efficiency the same way. A speed hump slows traffic at a point but can cause repetitive braking and acceleration and potential queues downstream, reducing efficiency. Diagonal parking mainly affects curbside access and sightlines rather than regulating through traffic speed, so it doesn’t achieve the same balance of slowed speed with higher overall efficiency.