Tag Archives: Lincoln

Westside Traffic, Peak Period Edition

A commenter on this post on Westside traffic asked if peak hour data might show different patterns, so I created similar graphics for the same roadways using the same data (Caltrans publishes peak hour, peak month, and yearly average traffic).

I’ll let the graphics speak for themselves. The peak hour patterns are quite similar to the total volume patterns, including the structural changes on the 405 and Venice coinciding with completion of the freeway widening project between the 90 and the 10. It’s actually a little surprising to see so much of a change in peak hour volumes – I would have guessed that changes in total volumes would be reflected in a shorter peak, leaving the peak hour itself relatively unchanged, rather than a more uniform change. These facilities are all near capacity, so if more cars enter the systems, peak volumes can only go up so much, and the increase would be expressed as a longer peak period and greater total delay.

I’ve put the daily volumes & peak volumes side by side so you can easily compare. Note that the y-scales are necessarily quite different. As always, click to embiggen.

Venice-both the405-both the10-both SM-both Lincoln-both

Is Westside Traffic Really Getting Worse?

Recently, the LA Times has published some articles positing that as freeway traffic gets worse, people have started using smart phone apps like Waze to try to avoid it, causing worsening congestion on neighborhood streets. The problem is that you can’t trust people’s perceptions of traffic. Traffic, like behavior of teenagers, is almost always perceived to be getting worse, data be damned.

Since Caltrans publishes freeway traffic counts going back to 2002, we can take a look at the evolution of Westside freeway traffic leading up to the last economic peak, the crash, and the current period of growth. Here’s a plot of traffic on the 10 between Lincoln and Vermont, from 2002 to 2013.

How to read: traffic volume is the vertical component. Time represented on the diagonal from top left to bottom right. The location on the freeway is represented west to east on the diagonal from bottom left to top right. So, if you follow a diagonal line from bottom left to top right, you’re seeing traffic volume on the freeway build as you head towards downtown. If you follow a diagonal line from top left to bottom right, you’re seeing how traffic has changed over time at a particular point on the freeway.

For example, following the diagonal for 2013, we can see that traffic is below 250,000 vehicles per day from Overland west, and above 250,000 vehicles per day from National east (where the line leaves the green area and enters the yellow band). Following the diagonal for Vermont, we can see that traffic volumes were above 325,000 at Vermont from 2002 to 2006, then between 300,000 and 325,000 from 2007 to 2011, and then back above 325,000 from 2012 to 2013.

If these graphics don’t make sense, there are some simpler line graphs at the bottom of the post showing the same freeways for years 2002, 2007, and 2013.

the10-contour

What can we see? Traffic declined across the whole freeway from Santa Monica to downtown LA as a result of the recession. West of La Brea, traffic volumes have not recovered or have declined even further, though east of there, traffic has started to recover. No boom in traffic on the Westside on the 10.

Here’s the 405 between the 90 and Mulholland (Sepulveda Pass). Information is the same, but the rotation is a little different to better show different patterns. I left the interchange with the 10 off the plot because it made a large, confusing dip between Olympic and Santa Monica.

the405-contour

From Wilshire to Sepulveda Pass, traffic volumes on the 405 haven’t increased noticeably either. There has, however, been a large increase in traffic between the 90 and Santa Monica since 2007. This correlates to both the economic recovery and the project that widened the freeway between the 90 and the 10 (induced/latent demand is real!).

Since some Westside arterials are still Caltrans-numbered routes (Lincoln, Santa Monica, and Venice) we can also look at trends on those facilities. Here’s Lincoln from the 90 to the 10.

Lincoln-contour

From the 90 to Washington, traffic volumes fell in the recession and have not yet recovered to previous peaks. The stunning thing here is the drop of 10,000+ vehicles per day between Venice and the 10 freeway. It seems possible that the completion of the widening project on the 405 shifted some traffic from Lincoln to the freeway.

Further evidence for that conjecture comes from Venice between Lincoln and La Cienega.

Venice-contour

Roughly coinciding with completion of the freeway project, Venice saw a considerable increase in traffic in the vicinity of the freeway and points east.

Lastly, here’s Santa Monica.

SM-contour

Nothing really jumps out here. Traffic declined during the recession, and consistent with national experience, has not recovered to previous peaks.

There’s no clear pattern of increasing traffic on these roads, but that doesn’t necessarily mean the story about worsening traffic on side streets is wrong. Technology like Google Maps and Waze makes information about the road network more accessible, and it’s certainly possible freeway and arterial traffic growth has been muted by people using the side streets. The city’s traffic data is also available through the Navigate LA website; maybe some enterprising person with programming skills can figure out a way to pull it out! Either way, it’s apparent there have been some shifts in traffic patterns, which we’d expect to make congestion worse in some places.

Note: 2009 data was missing, so I made it the average of 2008 and 2010.

the10-line the405-line Lincoln-line Venice-line SM-line

Sepulveda Pass and LAX Transit

Since both of these topics have been in the news a lot lately, it’s about time for a look at north-south transit on the Westside.

Sepulveda Pass in Context

Before we start laying out transit lines, we need to understand the urban context of the area in question. This is especially important for rail transit and other high capital cost projects, because bad decisions will haunt us for a really long time. So…

First, in terms of network design, Sepulveda Pass is a world-class bottleneck, right up there with San Francisco Bay and the Hudson & East Rivers. Your reaction to that, might be, “well, duh”, but we need to realize the implications for network design. Jarrett Walker goes into more detail in Chapter 4 of Human Transit but the chief points here are that (a) more deviation from straight routes is acceptable at bottlenecks and (b) bottlenecks are natural locations for transfers between parallel transit lines.

Second, in terms of engineering and cost, Sepulveda Pass is a very challenging and expensive area. We’re looking at a 7-mile tunnel from Westwood to Sherman Oaks, hundreds of feet deep in the middle. Vertical access between the tunnel ends is difficult at best for ventilation, and impossible for a station or emergency exit. This suggests that within the current planning time frame, we’re only going to get one shot at transit through Sepulveda Pass, so we’d better do it right and get a ton of capacity out of it. In 106 years, New York has managed to build only seven crossings of the Hudson, to connect all of Manhattan, the Bronx, Brooklyn, & Queens with all of New Jersey.

Therefore, any tunnel through Sepulveda Pass should serve multiple transit lines on both sides, and provide as much capacity as possible. The stations at each end will be natural transfer points between the lines. It doesn’t make sense to go to the expense of building a tunnel that long if all it’s going to serve in the Valley is one LRT line on Van Nuys. The tunnel should serve at least two lines on both sides, and probably more. We don’t have to actually build all of the lines right away; the important thing is that the piece from Westwood to Sherman Oaks is built properly at the outset. This is probably a great location for one of Alon Levy’s large diameter TBM tunnels, with four tracks running from Westwood to Sherman Oaks, since there won’t be any stops in between.

This also means that the tunnel should serve rail traffic exclusively and have no auto lanes. In addition to having a lower capacity, auto lanes have much heavier requirements for ventilation. There’s also the question of what facilities auto lanes would connect to at each end, since it’s not like there’s a ton of spare capacity kicking around on the 405, the 10, and the 101. (Note: you could argue for a bus tunnel, using dual-mode buses, with exclusive lanes on arterials for the rest of the lines. I’m not going to get into a bus vs. rail analysis here, since the quality of the ROW is more important than the technology.)

Transit Lines Through Sepulveda

Now that we’ve established what the facility through Sepulveda Pass should look like, we can lay out some transit lines to go through it. In my mind, the logical candidates for north-south transit in the Valley are Reseda, Sepulveda (Valley section), Van Nuys, and maybe Balboa. (Anything east of Van Nuys, at least IMHO, is a future north-south line to connect to La Cienega.) There’s also the potential for east-west lines on Venutra, west to Warner Center and east to Burbank. On the Westside, the north-south candidates are Lincoln, Bundy/Centinela, Sawtelle, Sepulveda (Westside section), Westwood/Overland, and maybe, as a stretch, Avenue of the Stars/Jefferson.

Personally, I’d leave Ventura alone as a separate east-west project. Sawtelle is too close to Sepulveda (Westside), so it doesn’t make the cut. The appeal of the Avenue of the Stars/Jefferson route is that it would serve Century City directly from the Valley, but the resulting line has such poor overall geometry that it wouldn’t be very useful for anyone not going to Century City, so I think it’s out as well.

The other intriguing option, which has been suggested by Henry Fung elsewhere, is having the Westside Subway Extension turn north in Westwood and go to the Valley. Assuming the other lines would be LRT, extending the Purple Line would create some technical challenges (including differing vehicle width). I’ll leave that for a future post focusing on that alternative. This option would take care of Century City.

Here’s a rough plot of these options with reasonable stop spacing:

SepulvedaLAX-alllines

Don’t worry too much about the stop spacing for now; we’ll take a closer look at that in future posts. Remember, the important thing at the outset is to serve the right area and choose logical overall route alignments. You also might guess from this graphic that I’ve got some changes in mind for Metrolink in the Valley. Yet another topic for yet another future post.

In terms of sequencing, the consensus is that Van Nuys is the top priority in the Valley. On the Westside, Sepulveda (Westside) and Westwood/Overland are only ½ to ¾ of a mile apart, so whichever of the two is built first, the other should be built last. I’d do Sepulveda (Westside) first, if only because it’s more centrally located and spreads the wealth. It’d be useful to some future users of the Bundy/Centinela and Westwood/Overland lines, whereas those two lines wouldn’t help each other’s riders much. The argument for Westwood/Overland first is that it’s closer to Palms and Culver City, which are denser than Mar Vista, and it’s a good enough argument that you could probably talk me into it.

I’d sequence the lines as follows:

  • Van Nuys and Sepulveda (Westside)
  • Reseda and Lincoln
  • Sepulveda (Valley) and Bundy/Centinela
  • Balboa and Westwood/Overland (no Westwood/Overland if Purple Line is extended)

The benefits start immediately with the first line completed, and are amplified as additional lines are finished. To the south, future phases could extend the lines out Florence, Manchester, Century, Hawthorne, Sepulveda/PCH… more than enough possibilities to leave for a future post.

LAX Transit

Note that all these lines naturally converge near Sepulveda & Century, right at LAX’s front door, and would serve far more people than any LAX rail transit proposal on the board now. So in addition to serving LAX, basically at the future Terminal 0, this project would directly serve a couple million other people who might or might not be going to LAX. In other words, this plan would follow one of Jarrett Walker’s main principles: be on the way!

You might have noticed in the first graphic that I didn’t show any connection from the new lines to the Green Line & Crenshaw Line. Clearly, you’d want to provide that link somehow.

Here’s one option for an initial build with two lines. In this scenario, the Crenshaw Line would take over the Green Line’s route south of Aviation/Imperial, and the Green Line would be extended a mile west to meet up with the new Reseda-Lincoln Line. This gives the combined Reseda-Lincoln-Green Line and the Van Nuys-Sepulveda (Westside) Line front door access to LAX, with decent geometry and without making any through passengers go out of their way.

SepulvedaLAX-2line

I’ve violated my own rules on stop spacing in El Segundo, going to half a mile to provide a Green Line stop at Maple and a Sepulveda Line stop at Mariposa. With this level of transit service, easy access to LAX, the 105, and the 405, there’s no reason El Segundo’s business district couldn’t become LA’s third downtown.

Here’s an option for full build with four lines.

SepulvedaLAX-4line

In this case, I’ve routed Balboa and Bundy/Centinela together, and the line could be extended out Florence towards South LA, HP, Bell, Cudahy, Bell Gardens, and Downey – all dense cities that should get good transit use. I’ve also shown the Purple Line being extended to the Valley and up Sepulveda.

Again, don’t worry too much about the specific stations and routings – we’ll go into more detail on each option in the future.

To Bore or Not to Bore

The decision to tunnel is one of the biggest ones that must be made. Tunneling results in faster speeds and more reliable operations, but the higher cost can push project completion further into the future. Obviously, we’re tunneling through Sepulveda Pass, but on either side, it would be possible to do full tunnels, surface running with selected grade separations (like Expo Line and Crenshaw Line), or full surface running.

Any surface running segments are dependent on the ROW of the arterial roads. Contrary to popular conceptions of LA, the north-south arterials on the Westside are somewhat underpowered. Lincoln and Sepulveda (Westside) are two lanes each way with a center turn lane. Bundy/Centinela and Westwood/Overland are cobbled together, with pieces where the second travel lane is only provided during peak periods by sacrificing on-street parking (always a sign of desperation).

The situation is much the same on Reseda and Balboa, which have the same basic configuration as Sepulveda (Westside), but with more generous proportions. On Balboa, there are three lanes each way with no parking. Sepulveda (Valley) and Van Nuys are wider, at least three lanes each way with a center turn lane plus parking. In many places they’re even wider (presumably where there used to be transit ROW in the middle).

I was going to go into detail and compare grade separation options for each branch, but that would make this post much too long. Now that we’ve got the basic framework set up, we can come back and give each branch the attention it deserves in future posts.