I-5, I-405, and US 26
Portland, OR

Overview: This interchange lies slightly south of downtown Portland, Oregon, on the west shore of the Willamette River. I-5, the main north-south highway through Portland and the entire West Coast, enters at the bottom and leaves to the northeast, crossing a bridge over the Willamette. It has frontage roads to the south of the interchange, which are part of OR 43. I-405, a loop around downtown Portland that serves as an alternate to I-5, leaves the northern half of the interchange to the west. Parallel to and west of I-5 is Naito Parkway, also OR 99W. The southern of the two bridges over the Willamette, the Ross Island Bridge, carries US 26; to the west, US 26 travels north on Naito Parkway along with OR 99W. On I-5, the exit for I-405 is Exit 299B, and US 26 is Exit 299A.

Interchange Description: The junction of I-5 and I-405 is fairly straightforward, a variation on a directional T interchange. I-5 enters from the south, and its roadway continues north through the interchange to form an extended pair of ramps which join US 26 and OR 99W north of this photo. (There is also an at-grade intersection between these ramps and Moody Ave., at the north edge of the aerial view.) I-5 actually exits on a pair of ramps further south, near the US 26 bridge, and crosses the Willamette River on a double-deck bridge (NB on top, SB on the bottom.) A second pair of ramps leaves this roadway and becomes the mainline of I-405. Elevated ramps also connect I-405 to the north and I-5 to the north.
The southern half of the interchange is a little more interesting. US 26 crosses over I-5 with quite an elevation difference; as a result, no ramps directly connect the two. At the western end of the bridge approach, US 26 intersects OR 99W in a partial interchange; the ramp from US 26 WB to OR 99W NB/US 26 WB appears to be missing. In reality, traffic continuing on US 26 WB uses Kelly Avenue, which runs diagonally from the western end of the bridge to Naito Parkway. Another ramp branches off of this one, forming a cloverleaf-esque loop to join OR 43 southbound. Access to I-5 southbound is eventually available from here.
From I-5 northbound, access to the US 26 bridge is available, but not via a very direct path. Traffic must exit first to OR 43 (south of this photo). Once northbound on OR 43, it uses the U-turn ramp visible just northwest of the US 26 bridge over I-5. This brings it onto OR 43 southbound. In addition to providing access to all of the streets that only intersect OR 43 SB, this also allows traffic to exit after going under US 26, use another cloverleaf loop ramp, and get onto US 26 EB. This cloverleaf utilizes part of Gibbs St, which runs one block south of US 26. Instead of a simple right-turn slip ramp, traffic from I-5 NB to US 26 EB must turn 180 degrees to the left and 270 to the right, but the movement is available.

Comments: In my humble opinion, this interchange has a couple of shortfalls. First of all, I-5 has a high number of left exits and entrances. Northbound, all of the through traffic on I-5 must exit right, and the I-405 traffic which goes straight ahead here also must exit to stay on I-405. The main through roadway becomes an exit ramp to OR 99W north of this photo, while both through highways must exit. Likewise, southbound traffic on I-5 and I-405 have left entrances, not to mention the left exit on I-5 SB for I-405. Also, although it's not terribly crucial, I think a better, less convoluted path from I-5 NB to US 26 EB would be advantageous. This connection is one of the only ways for I-5 NB traffic to easily get to many of the neighborhoods of southwest Portland, and it is fairly indirect with many turns.

• I-405 at kurumi.com

• I-405 at interstate-guide.com - Photos of the southern terminus