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Turbo-Roundabout

INT-TRB-02
Recommended Intersections & Crossings

Turbo-Roundabout

A roundabout variant using spiral lane markings and raised lane dividers to guide multi-lane traffic without the weaving conflicts a standard multi-lane roundabout allows.

Typical at: Compact Urban

Suburban and Core are edge cases. Undeveloped and Rural are unlikely pairings.

#Design notes

Reserved for higher-volume Arterial-to-Arterial junctions, where a standard roundabout's capacity is not enough but a signal is still not the preferred default. This keeps the roundabout-first philosophy intact at higher volumes rather than defaulting to a signal once traffic grows.1

Roundabout (Single/Multi-Lane) (INT-RAB-01) (the base pattern this scales up from), Signal (INT-SIG-03) (explicitly named on this page as the alternative not preferred even at these volumes)

#Getting there: Retrofit path options

Signal-to-roundabout conversion (RFT-INT-01)

#References

  1. Evidence-based Fortuijn, L.G.H., "Turbo Roundabouts: Design Principles and Safety Performance," Transportation Research Record 2096 (2009).(opens in new tab)

Suggest changes to this page (opens in new tab) Text-only version Last updated September 26, 2026