reasonable speed

Definition from Nolo’s Plain-English Law Dictionary

The speed at which it is safe to drive an automobile considering road conditions and other circumstances, such as rain, ice, heavy traffic, the vehicle's condition, or visability. Reasonable speed may be less than the posted speed limit. Drivers who exceed reasonable speed can be cited for speeding or may be found to be negligent even if they were driving within the posted speed limit.

Definition provided by Nolo’s Plain-English Law Dictionary.