Well, I personally use the phrase cash a check to mean that I'm taking a check to the bank to get the amount in cash. Others probably use it interchangably to mean deposit a check, which I'd say means taking a check to the bank with the intent to deposit it (either in full or partially) into an account. YMMV.
Advisory speed signs have a great advantage over speed limit signs: Rather than being based on decisions of governmental agencies, the numbers on advisory speed signs are to be based on a law of physics. This is the law stating that a moving object will continue in the same direction unless acted upon by an outside force.
So the 85th percentile rule is simply a recognition that speed limits are set for the purposes of enforcement. And since law enforcement only has the resources to cite the most egregious violations, the speed limit is established at or near the 85th percentile, making only about 15% of free-flowing motorists violators.