Not always.
There's a stretch of highway south of town (Milwaukee, Wis) that used to be posted 65 mph. A few years ago, they dropped the speed limit to 55 mph. A few days ago, they raised it back to 65 mph to reduce accidents. The number of traffic accidents on that stretch of highway INCREASED when the limit was reduced from 65 to 55.
Not trying to cause a dispute; just pointing out an interesting factoid that goes contrary to what you would think.
Brian Bronson