When may drivers use hand and arm signals instead of signal lights?

Drivers are permitted to use hand and arm signals instead of signal lights when their signal lights are not functioning. This is a crucial safety measure, as it ensures that drivers can still communicate their intentions to others on the road, despite the malfunction of their vehicle's signaling system. Proper signaling is essential for the safety of all road users, as it helps to prevent accidents by informing other drivers of turns, stops, or lane changes.

In situations where the signal lights are operational, it is expected that drivers use them as the primary means of signaling. However, if these lights are defective, using hand and arm signals becomes not only acceptable but also necessary to convey one's driving intentions effectively.

Other scenarios described in the choices do not warrant the use of hand and arm signals. For instance, it is still expected that signal lights be used at night or in adverse weather conditions, as visibility can be compromised in these situations. Additionally, the legality of using lights does not impact the need for signaling; proper signaling should always be practiced when driving, regardless of whether it's day or night, rainy or clear.