Why can modern roundabouts reduce severe crashes compared with conventional four-way intersections?

Answer: Their curved paths slow vehicles and reduce crossing conflicts

Their extra lanes give every crossing vehicle its own lane — A roundabout need not have extra lanes; many have only one circulating lane. Its safety benefit comes from slower paths and fewer crossing conflicts, not a separate lane for every vehicle. Lane count alone does not determine how safely traffic movements meet.

Their entering traffic always has priority over circulating traffic — Entering drivers normally yield to traffic already circulating, not the other way around. This helps merging traffic join the same flow instead of crossing it at high speed. Together with the curved, slower paths, that reduces the chance of severe crossing collisions.

Their curved paths slow vehicles and reduce crossing conflicts ✓ — Curved approaches slow vehicles and redirect crossing movements into a shared circulation direction. Lower speeds reduce impact severity, and a typical single-lane four-leg roundabout has 8 vehicle conflict points rather than 32 at a conventional four-way intersection. This geometry reduces opportunities for severe right-angle and head-on crashes.