I think the idea being referred to is the 85th percentile speed. Here's a news article that talks about it: http://articles.latimes.com/2005/mar/09/autos/hy-whe

I think the idea being referred to is the 85th percentile speed. Here's a news article that talks about it: http://articles.latimes.com/2005/mar/09/autos/hy-wheels9 http://articles.latimes.com/2005/mar/09/autos/hy-wheels9