New 405 south to 101 interchange in the works

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posted: 2:05 p.m.

Caltrans today announced its preferred method for improving the 405-101 freeway interchange, which the agency says is one of the busiest in the world. But don't get too excited. The agency also says that it doesn't have the money to design or build the project, which is expected to cost about $135 million.

Still, this is one of those classic bottlenecks, and understanding why it doesn't work helps explain a lot of other bottlenecks on Southern California freeways.

The big problem is that entrance and exit ramps have been placed too close to one another. The particular issue on the 405 is that traffic trying to merge onto the freeway from the Burbank Boulevard onramp immediately must merge with traffic trying to leave the 405 for the exit to the 101 (the big yellow arrow is pointing to the ramp from the 405 to 101).

That means a lot of weaving and braking, the reason that the area scores low on Caltrans' measurement of traffic speeds. Between mid-2004 and mid-2007, that particular portion of the freeway also had a significantly higher accident rate than the statewide average (1.45 accidents per million miles driven compared to 1.09 per million miles driven statewide).

The other big mess is the ramp from the 405 south to the 101 west/north. It's a very tight turn and only a single lane. Caltrans says the ramp was built to handle up to 1,500 cars per hour, but during the morning rush on weekdays it averages 1,792 vehicles. The afternoon rush is better, but only slightly, with an average of 1,374 vehicles per hour using the ramp.

Two design flaws are obvious with the current setup: traffic trying to get onto the 405 from Burbank Boulevard has to merge into traffic trying to exit the 405.

Here's how Caltrans is proposing to fix it:

1. The existing one-lane ramp from the 405 south to the 101 west/north would be replaced with a two-lane ramp that allows speeds of 50 mph. In addition, the ramp would enter the 101 west of the 101's exit to Haskell -- so incoming 101 traffic doesn't have to mix with 101 traffic trying to get off the freeway.

2. The Burbank Boulevard on-ramp would be routed under the new 405-to-101 exit ramp, so that traffic won't enter the 405 south until after the 101 exit. That also eliminates access to both directions of the 101 for those entering the 405 from Burbank Boulevard.

3. The new two-lane bridge from the 405 to the 101 would cross the spillway away of Sepulveda Dam. Caltrans is saying the new bridge would be designed to match the dam's architectural style.

These types of bottlenecks are all over the region, where entrances and exits to freeways were built too close together. My favorite is in Pasadena, where traffic on the westbound 210 trying to exit to the leg of the 210 that continues to La Canada-Flintridge and beyond must mix with traffic trying to get on the 210 from four different entrances.

I asked Caltrans spokesperson Judy Gish if there was a timeline for the project. "There is no timeline because there are no funds at this point," she said. It should be noted that the proposal to increase the sales tax in L.A. County -- which may go to voters in November -- does not include money for this interchange.

What do you think? Will this work? Do you believe it will ever happen?

--Steve Hymon

Comments

[Concernicus]

How about bringing in private investment capital to help fund some of these projects. $135 million for this project is much less than 1% of the $500 billion California needs to find over the next two decades to fix our state's roads, highways, bridges and other areas of infrastructure.

Hey our bad, California forgot its wallet, can anyone spot us $500 billion?

[Daniel - The California Highway Guy]

I realized something while thinking about this on the way home: They didn't say what they were going to do to address the 405SB to 101SB(EB) problem. Right now, it dumps slow moving traffic into the #1 lane, which creates a merging problem as well. Ideally, they will do a flyover ramp, but those are very pricy, plus they don't have the merge room with the other 101 ramp (405NB to 101SB).

[Jose]

These kinds of ramps work, some more effectively than others. In OC, the ramp complex on the 405 both north and southbound around Harbor Blvd down to Bristol Street has been redesigned just this way and there is much less traffic crossing than there was before. Almost perfect.

They also did a project like this where the east 22 meets the north 55 that took the Chapman off ramp traffic away from the merging traffic from the 22 - a great success.

But then they tried this sort of thing between the east 22 and the south 5 and totally goobered it up.

[Tommy]

So wait, this project ONLY costs $135 million? That seems like a bargain to me, compared to the BILLIONS of dollars we've been hearing for other projects. And this project seems like it would be a substantial improvement. I don't get it; looks like a no-brainer to me.

As for my (least) favorite bottleneck, being from the westside, I would have to nominate the 10-405. If you enter the 10 east on Centinela Avenue, almost immediately you are dealing with the people merging from the Bundy on-ramp. Then after that you run right smack into the hordes of people trying to get on the 405. In terms of distances, the Centinela and Bundy on-ramps are separated by a mere 1000 feet. The 405 north ramp is then only 1500 feet east of the Bundy on-ramp.

[Richard Hendricks]

Here's a novel idea: permanently close the Burbank on ramp. That'll take care of one of the bottlenecks at the interchange.

[Cahwyguy - Daniel]

I can see exactly (in my head) what they are trying to do -- in many ways, it is very similar to the improvements they made on the other side of the intersection (405 NB to US 101). Will we see it? Good question. Given that the Federal Highway Trust Fund is in deficit, higher prices meaning fewer miles driven and more efficient cars will mean less income to Caltrans from Collier-Burns monies, this would only come through bond funding. Knowing the CMIA, SAFETEA-LIU, SHOPP, and TCRP planning is already done and funding, I don't think we're likely to see construction start for at leat 6-8 years, and then the project will be at least a 5 year project. Will traffic at that time justify it? Hard to know, given where gas prices will be.

But thanks for the useful information.