wunder beta🔄 How Roundabouts Work
The car in the circle will not stop for you. Yield, join a one-way stream, and leave — the pavement does the slowing that a red light used to do.
What you’ll learn
- Yield, then joinDistinguish a modern roundabout from a traffic circle and walk the yield-gap-circulate-exit sequence.Entering traffic yields to a one-way circulating stream. Direction follows the driving side. Capacity is an entry problem, not a whole-circle average.
- The pavement does the slowingConnect deflection, conflict-point counts, and crash-severity numbers to the geometry.Splitter and central island force a slow curve. Four single-lane legs drop from 32 vehicle-vehicle conflicts to 8. Severe crashes fall; remaining crashes are lower energy.
- People, lanes, and when not toPlace pedestrians and cyclists correctly, explain the multilane penalty, and name sites that should not get a roundabout.Crossings are two-stage and set back. Bike lanes never run through the ring. Extra lanes buy capacity and spend simplicity. Unbalanced demand, tight signal strings, and missing right-of-way can rule the circle out.
Questions this course answers
Who usually has priority at a modern roundabout entry?
Entering drivers yield to circulating traffic. The circulatory roadway itself has no routine stop or signal.
Match the feature to the intersection type the FHWA guide would call it.
A roundabout must use yield-at-entry and circulating priority. Circles that reverse priority, add parking in the ring, or skip deflection are a different device.
Put a through trip in order.
Geometry slows you, the yield line sequences you, and you leave without stopping in the ring.
For a four-leg intersection with single-lane approaches, how many vehicle-vehicle conflict points remain after conversion to a single-lane roundabout?
FHWA's Informational Guide counts 32 vehicle-vehicle conflict points at the conventional four-leg intersection and 8 at the single-lane roundabout — a 75 percent drop. Extra lanes add conflicts back.
What does FHWA report for fatal and injury crashes when a two-way stop is converted to a roundabout?
The Proven Safety Countermeasure sheet, citing the Highway Safety Manual, reports an 82 percent reduction in fatal and injury crashes for two-way-stop conversions, and 78 percent for signal conversions. Remaining crashes still happen, usually at lower energy.
Why is the pedestrian crossing set back from the yield line?
The splitter island is a refuge. The setback shortens each stage, separates vehicle-vehicle conflicts from the crossing, and gives the second entering driver a chance to watch the crosswalk.
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