The problem is that the speed limit itself has nothing to do with safety. To take your example of Seattle, there are 4 lane main roads with a 25 mph speed limit that in any other city would be 35 to 45. And everybody drives 40-45 on the anyway.
Those are the worst, because there's always a huge speed differential between the "law-abiders" who stay at 25, and the others who drive the speed the road was obviously designed for (40). Felt a lot safer when the limit on them was actually 40 and everyone was more or less going the same speed.
