I know that there have been quite a few 4-to-3 lane conversions (from 2 travel lanes each way to 1 lane each way w/ BL or WOL+center turn lane) done to improve roads. Traveling around town, I was wondering whether there exists a reasonable solution to include BL/WOLs for exisitng 5 lane roads (2 travel lanes each way+center turn lane). If such schemes exist, I'm guessing they can be implemented w/o costing a lot., and could be done whenever the roads are scheduled for repaving when the markings would have to be redrawn anyway.

Speaking of which, are there studies out there that show the net effect on road capacity for such conversions? The reduction in travel lanes reduces car capacity; yet the added turn lane, combined with the addition of friendlier bike accomodations, adds capacity. It would be interesting to see how these factors balance out.