I have been riding the Sammamish River and Burke Gilman trails off an on for years and due to a increasing frequency of encounters with well meaning but a little too casual users of the trail, I'm thinking I should look for an alternative route for my long rides.
I have a routine ride route near my home that gets me a good 25K distance with a mix of descents and climbs that help me build strength. But, what I need is a route that has a low traffic interaction level and can support either an out-n-back or a loop of 50K to 75K or relatively flat riding (can be any mix of hard pack "dirt" trail or paved... My cross bike can deal with either.)
What I'm looking for is a route where I can work on sustaining a 25KPH to 32KPH pace without too much interaction with large families of casual bikers (no a comment on them... just trying to find a route where I won't annoy them and they won't interfere with me)
I've got a great hill route near me that has virtually no traffic and is about 15K, but due to the hills isn't a very good pace training route.
Yeah, the serious cyclist should just stay away from the BG/SR trail. It only frustrates the one trying to get in a good workout, and annoys the families that think it's a paved playground. Either that, or get up good and early. At 7 or 8 on a Sunday morning all I ever see are training athletes, and not even very many of those.
That said, I'd look on Garmin's site (connect.garmin.com) or Strava for courses near you. Neither will give you traffic data, but you might make an educated guess (the King County bicycle map might help there). If DM has a course search function, I've never seen it.