Zürich grades its cycling network in three tiers. The safest-route
finder here doesn't just take the shortest path — it treats these as
cheaper to travel, so a route will happily detour onto a Vorzugsroute
rather than take a shorter but harsher road. Vorzugsrouten pull
hardest, then Hauptnetz, then Basisnetz. Accident history pushes the
other way.
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