When passing another vehcile, when is it acceptable to drive over the speed limit

When the vehicle in front of you is proving to be an imminent danger to yourself, such as the driver texting and driving, driving recklessly, etc.

There is a do not pass sign on the roadway. A vehicle that is already going close to, or above the road's speed limit; this is because when you pass that vehicle that speed, you must go at least 10-15 miles per hour over the speed limit, which is illegal.