- Improves
traffic flow along southbound I-5, i.e., mainline level-of-service
(LOS) improves from near-capacity conditions (LOS "E") to high-density
and stable flow (LOS "D").
- Keeps "freeway"
traffic on the freeway: e.g., reduces traffic diversion to Interstate
Avenue/Denver Avenue (southbound off-ramp volume decrease by
about 500 vehicles per hour), decreasing neighborhood cut-through
volumes.
- If added
lane is an HOV lane during the morning commute period, reduces
HOV travel times from Salmon Creek to Portland by over two minutes.
- Provision
of standard freeway shoulders, in both the southbound and northbound
directions, would improve safety and the ability to respond
to incidents.
- Reconfigured
southbound on-ramp merge from Columbia Boulevard operates acceptably:
- Existing
ramp has a rising grade of six percent and enables heavy trucks
to attain speed of only 25 mph when entering the freeway.
- Proposed
ramp would have a four- percent grade and a 1,400-foot long
acceleration lane parallel to the third freeway lane. Ramp would
enable trucks to attain a speed of 45 mph within the acceleration
lane before entering freeway.
- The new
on-ramp merge would operate at level-of-service "C-D" during
peak periods, indicating generally smooth merging conditions.
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