As anyone knows who drives the region’s freeways, one chronic source of backups is when heavy traffic must cope with an entrance ramp followed closely by an exit ramp. In other words, traffic trying to move left from the entrance lane mixes with traffic trying to move right to exit. The result: a chokepoint causing traffic to back up on the freeway and on surface streets.
There’s a good post on County Supervisor Zev Yaroslavsky’s website explaining that part of the 405 Sepulveda Pass Improvement Project aims to help such a situation at the 405’s junction with Wilshire by building flyover ramps for the northbound and southbound sides of the freeway. As the map above shows (the rendering only shows the southbound ramps), the flyover ramps allow traffic exiting to eastbound Wilshire to leave the freeway before traffic from westbound Wilshire enters.
That, I think, is a key improvement that hasn’t received as much attention as the carpool lane that is being added to the freeway. Of course, it will come with construction headaches, with work expected to begin as early as February. More on that soon and we should be able to show a more detailed rendering next month.
Work expected to begin in February? Like ralph mentions, this is already being constructed, and the large I-beams are in place. Why is there his strange disconnect going on? Obviously the design must be done now, it is just nice to know when it will be DONE.
Follow through is a done deal. Three of the four abutments (the structures that support the ends of a bridge) are aleady under construction in that the steel “H” piles have been put in place to support the future foundation structures. That’s the blue line above. The I-405S to Wilshire West ramp will have two bridges (one over the on ramp and one over Wilshire). What is unique about this construction is that because the abutments are fairly high above the surrounding area, the contractor only put the foundation piles partway into the existing ground and now is building up the ground around the piles to get up to the file elevations needed. This is why if you drive by the area you’ll see these beams sticking up into the air right now.
Segments with weaving traffic like the current Wilshire Blvd. interchange are quite dangerous.
If they follow through with this idea, we will get a rather nice braided cloverleaf interchange like at Victory Blvd. on the Hollywood Freeway.