To Fight Gridlock, Los Angeles Synchronizes Every Red Light

[cletus]

New York City clearly uses a similar system if you've spent any time in Manhattan at all.

North of 14th Street the city is almost entirely on a grid (Broadway runs diagonal and there are a couple of other exceptions). This has, at least from my observations, had three distinct advantages:

1. Building subways has been relatively easy (a lot were built by digging long straight tunnels and building the avenue over them);

2. Almost all streets are one-way, which greatly simplifies lights. A lot of cities have gone away from one-way streets because it "confuses" drivers despite it being clearly better; and

3. The lights are synchronized.

Now not all city's have NYC's regularity but the Manhattan grid has to go down as one of the greatest forethoughts in urban planning ever (IMHO).

Anyway, it's interesting to see this work so well in cities that are less regular.

[DannoHung]

And yet getting across town is still a pain and a half.

[seanmcdirmid]

Next step: all cars are driven automatically and completely synchronized within the city. The capacity gains we could achieve would be astronomical, while parking would become a thing of the past (just treat them like taxis).

I'm very excited about what cities will look like in the future!

[StavrosK]

Sometimes I like to imagine what the world would be like if we could have portals. Imagine a door with a keypad, you dial the number of the door you want to connect to, the other end authorizes it and you get portals between the two. Tourism would instantly stop existing, because everyone would live everywhere. The super market would be, literally, next door. The post office would stop existing, Amazon deliveries would be next-second. You might not even need stuff, just pool them with your friends in a shared storage locker for all of you to use.

It'd be amazing.

[sk5t]

Every time I'm waiting to move past a red light, I wonder what the gains would be if all the dopes in front of me (and piloting my car, and the ones behind me) accelerated more-or-less in concert. It is very, very annoying to wait for the "wave" of moving to work its way back, once you become aware of it...

[mmanfrin]

This is my hope for Google cars. Autodriving taxis -- make them with all electric vehicles that stop for recharge when they're low and are replaced by another fleet vehicle? Perfection.

[swah]

In your future, why do we still have to move?

[thrownaway2424]

How does one synchronize every light? Imagining a grid, I can think of how every 1-way northbound and southbound street can be individually synchronized, but then in my imagination the east and west streets are befucked. So how does it actually work? And how do you synchronize a 2-way street?

[moocow01]

Id imagine that you are attempting to move cars down every street in "waves". It almost might be more helpful to think of it as a series of trains on each street. You likely can stagger the trains going north to south as well as the trains going east to west so that they miss each other. Its probably more complex than this but I'd imagine this is the basic concept.

[lobster_johnson]

I suspect that by "synchronized" they simply mean "coordinated" -- that they are automatically controlled by a computer that attempts to optimize for flow.

So for example, an intersection will be kept open in one direction as long as there are no crossing traffic. And if the same is the true about the next intersection, the light will be green there too; based on the sensors, the system can gauge the amount of traffic going towards the next intersection, and prioritize the flow. So if there are a lot of cars going towards an intersection, and a single car arrives that needs to cross their lane, the system may favour the group and prolong the green light.

In that sense it's synchronization, as "adjacent" lights will be considered by the algorithm.

[vacri]

It's bad terminology. The lights aren't synchronised, they're centrally managed or centrally co-ordinated.

[thatcherclay]

This is great - wish the government would go the next step and open up the traffic optimization to the general tech/data community to help. Think of Netflix recommendation challenge, but helping millions of people cut down on their commute.

[gamblor956]

Quite effectively, too. My average commute is now 10 minutes less each way. The difference after they got every light into the system was immediately noticeable.

[melling]

Average speed has increased to 30mph? Sure, it sounds like a great system, but wouldn't it be even more helpful to have a few hundred miles of subway/rail? LA seems to be expanding but for city of that size, it should probably have more rail than NYC.

http://en.wikipedia.org/wiki/Metro_Rail_(Los_Angeles_County)

http://en.wikipedia.org/wiki/New_York_City_Subway

[dmnd]

This is offtopic, but it caught my eye.

> President Obama’s visit here in August 2010, for example, forced the closing of a major thoroughfare, unleashing gridlock on the entire west side of the city.

Is it really necessary for the passage of one person to cause so much delay for everyone else? Why would a thoroughfare close for the president, anyway? Security?

[ricardobeat]

Yup. It's amazing how a small interruption (or even closing a single lane) in a crossing can snowball into huge traffic jams.

[NathanKP]

I agree it would be nice if this was open sourced, but I think the biggest barrier most cities would face stopping them from implementing a similar system would be the colossal hardware costs, not the software.

[salem]

Fact Check: "the first major metropolis in the world to do so" N.S.W. Australia has had a coordinated traffic system since the 60's, lights have been coordinated across Sydney for decades. They may not be synchronized to the extreme that LA's system could be, since Sydney doesn't have such as massive grid of streets, but there is a system wi view of state. http://www.scats.com.au/product_history.html

[jessriedel]

Slow down, mate. New York City's lights have been synchronized for years too, and I doubt the NY Times missed that. The first part of the sentence you quote contains the key detail: "Los Angeles has synchronized every one of its 4,500 traffic signals across 469 square miles..."

[chrsstrm]

The real issue here is the queue of cars waiting to get on the freeway. Any street that crosses a major freeway and offers an onramp can be backed up for miles in both directions. Synchronized lights may help with purely street-level congestion, but increasing throughput on the freeways is what will really clear the streets. I've clocked travel times of anywhere from 1-1.5 hours to go 8 miles, and all of the wait was due to congestion at the onramp.

[bprater]

You have to wonder why they are using magnetic strips -- in an era with tons of computing power, video would make more sense. Especially with a $400mm investment!

Not only could a human agent watch the street from a command post, but computers could make decisions based on what people are currently doing in their cars down the street.

[gcr]

I disagree. What advantage would video provide over magnetic strips?

Magnetic strips are (likely):

- Cheaper than setting up and powering video cameras

- Resistent to harsh conditions (eg. good luck hiring someone to go around town and wiping all the foggy camera lenses during a rainstorm)

- Likely to last longer than a video sensor

- Probably more accurate than video, too

- Doesn't need a huge computing infrastructure to monitor and interpret

- Respects pedestrians' privacy more

[khuey]

Nit: they're inductive loops, not "magnetic strips".

[sixothree]

My city has the exact opposite. The signal lights have antennas and communicate with one another, but it only guarantees that a pack of cars leaving one light will always sit through the entire duration of the next light.

It's horribly inefficient, which is one reason I suspect it is like this - gas taxes.

[mmanfrin]

SF does this with the Fell/Oak one-way avenues. I absolutely love them, with the exception of when people stop in one of the three lanes to try to park, which gums up the entire system.