Kentucky has recently started using 6" centerline and edgeline striping on non-freeway routes. The plan is to start with routes classified as primary (Kentucky has primary, state secondary, rural secondary, and supplemental as its classifications) and eventually stripe all state routes with 6" striping as opposed to 4" striping.
The stated purpose is that the wider stripes are more visible, and thus safer. But I've noticed something else too. New striping on resurfaced state secondary roads is 6", this makes the travel lanes appear much narrower than they did before with the 4" striping. Obviously, the physical width of the roadway is unchanged, or if anything, it might be a little wider because sometimes gravel shoulders get paved. I just wonder if the narrower appearance is an unintended consequence, and it slows traffic down because the road appears narrower?
WVDOH moved to 6" striping a couple years ago. It does seem to subtly narrow the lanes, although I've not really observed any difference in traffic speeds from it.