In Illinois, when is it illegal to make a right turn?

Making a right turn at a red stop signal without a sign permitting it is illegal because traffic laws are designed to ensure the safety and flow of vehicular and pedestrian traffic. In Illinois, a driver must come to a complete stop at a red light and only proceed when it is safe to do so, unless otherwise indicated by a sign that allows for a right turn on red after stopping. This rule is in place to prevent accidents, as turning right at a red light without stopping can lead to collisions with oncoming traffic or pedestrians who may have the right of way.

The other options do not reflect the traffic laws accurately. A yellow light indicates that the light is about to change to red, and drivers should prepare to stop, but it does not specifically prohibit a right turn unless the light has already turned red. Saying that it is illegal to make a right turn at all times or only on weekends is incorrect, as those assertions do not align with traffic regulations which allow for right turns under certain conditions.