Seattle to Mukilteo Ferry Terminal

The first step to reaching Whidbey Island (which includes Deception Pass, Anacortes, and connections to Canada) is getting to the Mukilteo Ferry from Seattle. Here's the route I use; it tends to follow the best bicycle roads and trails that parallel Highway 99:

View Mukilteo To Seattle Center in a larger map

The total length of the entire ride from roughly the Space Needle to the Mukilteo Ferry Terminal is about 27 miles due north. 

   Segment 1: Seattle Center to start of Interurban Trail
 Length:                  TBD
 Type:          Roads, mostly with bike lanes or residential streets
 Route:  Connect to the Fremont Bridge via the South Lake Union bike trail, once across the bridge, continue north for about a mile on Fremont Ave to 50th, across from the zoo. It's about a mile uphill, the first major climb. There's a bike lane the whole way. Turn left at 50th and follow the bike lane around and onto to Phinney.

Stay in the bike lane on Phinney to 83rd, and then cut over to Dayton to cross 85th, and then jog over to Fremont Ave.

Fremont Ave will take you to the start of the first paved trail segment of the Interurban Trail. It's also has a bike light at 105th, making it easy to cross this busy street. This view is looking south:

From here, the start of the Interurban will be to your right at 110th St.

Start of trail (aka southernmost point):

   Section 2: Interurban Trail
 Length:      TBD
 Type:      Nearly all paved trail, with some short sections of road riding.
 Route:  The first section of paved trail runs from 110th to 130th, where the trail ends and you must ride Fremont Ave (no bike lane, just sharrows, light traffic) to the beginning of the main section of the trail at 145th.

The end of the first section (near 130th), looks like this:

After you ride past Bitter Lake Playfield, the main segment of the Interurban begins at 145th. From this point, it's a well-signed route through Shoreline, with two very nice overpasses for 99. There's some twists and turns and crossings, but you can ride all on paved trail or sidewalk until you hit the first break in the trail at 200th near the Aurora Transit Center.

At this point, you turn right (east) and follow the bike lane on N 200th up a hill to the intersection with Meridian. Cross Meridian and the trail resumes for a short downhill to the intersection with 205th. This is a busy intersection, but once across 205th, there's a wide shoulder. Follow 76th to 228th, there's plenty of signs. Head right (east) on 228th and watch the signs. The paved trail resumes by a small power station between 73rd and 72nd.

From here, follow the trail to the junction with 44th. There's a couple of small sections on road, but the route is well-signed and easy to follow:

The Interurban Trail continues across 44th and along I-5, but at this point, you want to break off and stay on the sidewalk along 44th.

  Section 3: 44th to Ferry Terminal
 Length:  TBD
 Type:      All road, most with bike lanes.
 Route: 44th Ave W is a busy road, especially around I-5; I recommend riding on the sidewalk until you get beyond 194th, where the road narrows and the shoulder is easier to ride on.

Continue on 44th till you get to 168th SW, where you cross 99. This area is fairly busy as well, just use the crosswalks and you will be fine. Once on across 99 on 168th, follow 48th to 148th SW/aka Norma Beach Rd. Turn right (east) and take the bike lane to 47th.

From here there's several ways to go; if you stay on 47th Ave as its becomes 45th Ave then 143rd PL, then 45th PL and make a right a on Shelby, you will connect with Beverly Park Rd.

There's a bike lane on Beverly, follow it to 525, the Mukilteo Speedway. With a name like that, you know it's busy, but there's a broad bike lane and sidewalks. I have never had any problems riding in this area. 

Be aware of the exit ramp to 526, there's a direct crossing of fast traffic, make sure to wait for a wide gap. 

It's all downhill to the ferry (and quite a climb on the way out). To board the ferry, don't follow the cars, but go directly to the window for walk-ons directly ahead of the stop sign where 525 ends. Board with passengers, no charge on the ride back from Clinton to Mukilteo.
 Notes and References: