When changing lanes in Oregon in a passenger vehicle, when are hand-and-arm signals acceptable in place of turn signal lights?

Night use of hand-and-arm signals is not acceptable on any Oregon street; the manual requires turn signal lights at night regardless of neighborhood. This answer blends the darkness restriction with a made-up neighborhood carve-out, treating quiet streets as calm enough to waive the night-lights rule.

Even when your signal lights have failed, hand-and-arm signals are still limited to daylight with 1,000 feet of visibility; lamp failure does not extend the window into night or poor conditions. This answer treats a broken turn-signal lamp as a blanket exception, borrowing the common fix-it habit drivers reach for when equipment breaks rather than the manual's daylight-and-visibility limits.

Hand-and-arm signals are limited to daylight when you can clearly see people and vehicles at 1,000 feet; at night or in poor visibility you must use turn signal lights. This answer half-remembers hand signals as a universally accepted backup, likely from driver's-ed diagrams that show the three arm positions without noting the daylight-only limit.