The tracks are one degree apart so in round numbers 60 miles. There is talk about going to half degree separation sometime in the future. It is in effect RNP 12.6 now going to RNP 10 in January of 2015. The tracks are defined in the daily track message and are designed to take advantage of tail winds and minimize headwinds. There are two sets of track each day. One runs from 01z until 08z and is designed for eastbound flights. The other runs from 11:30z until 19z and is set up for westbound flights.