To Fight Gridlock, Los Angeles Synchronizes Every Red Light | Hacker News Reader

To Fight Gridlock, Los Angeles Synchronizes Every Red Light

nytimes.com

46 pointsolegious60 comments

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.

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

I was about to respond with a knee-jerk "Try it in Dallas around 5:30pm, or in Austin any time between 3pm and 6pm", but I guess it's all subjective.

I'd rather spend 45 minutes standing up in the subway, free to zone out or read a book, rather than 30 minutes stuck in stop-and-go traffic. (And definitely rather than 2 hours stuck in the same traffic.)

I think he meant getting "crosstown" meaning going east to west or vice versa. This requires taking one of 3 subways, a bus, taxi or walking. It is a pain compared to the myriad of ways to get north and south.

Oh, right. Yeah - I live on the west-most side of Harlem, and I'm basically resigning myself to never seeing any of my friends on the Upper East Side.

or in Austin any time between 3pm and 6pm

I think you mean "or in Austin any time between midnight and 11:59pm the next day.

Used to live in a condo with a direct line of sight to 35, it would be no shocker to wake up at 2am, walk to the bathroom and glance out my sliding glass door randomly to see 35 backed up.

When I lived in NYC over the summer, one of the things that blew my mind was how easy and cheap and quick it was to get anywhere in the city. YYMV though, I guess.

It's not that it's hard, it's just that a cab ride from 1st Ave and 34th to 10th Ave and 34th is gonna take like 15 minutes at least.

Which is ridiculous because it's about a mile.

Driving in Manhattan is great... when there's no traffic and you don't need to park.

New York can fix those problems easily, but they have some sort of Stockholm syndrome with their unbelievably terrible traffic situation. But when it's not rush hour, you can cruise twenty blocks at a time through Midtown before you hit a short red light. That's pretty nice. Everything's on a grid, one-way streets follow a pattern, and there's a lot of neat stuff to see as you drive.

I never experienced much bad traffic in NYC, at least nothing compared to Beijing at 9PM.

A walk from 2nd to 7th isn't that bad. Agree, though, could use another crosstown like the L somewhere else. I hate buses.

This is because the lights are synchronized to make north-south traffic fast, which is a smart trade-off made because of the island's shape.

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!

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

People like freedom of travel? It would be depressing to spend all day at home, even if it was possible.

If we're only travelling when we like, we might as well drive the cars :)

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...

There would still be some slack in the movement, we could just reduce it substantially. Couple auto car pilots with electric drive trains that provide dependable and fast acceleration...that slack could be very small indeed!

But then, if all your cars were controlled automatically, why would you even need to stop. They could mostly just slow down and hit the lights when they were always green! Perfect synchronization!

Or have no traffic lights and the cars intersecting detect and adjust speed accordingly/create gaps/etc (would look/be scary but it'd work).

The wave exists because you need following distance to drive safely.

Also, because people have relatively slow reactions. A computer could do much better, of course, and still preserve a reasonable amount of safety.

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.

You need to read The Stars My Destination by Alfred Bester.

I'll give it a try, thank you.

The Hyperion series by Dan Simmons also had a great envisioning of the use of portals (multidimensional houses, the endless river) and a secret downside.

I like the idea of making the cost of transportation negligable.

We'd waste less oil than we currently do.

Crime would be much simpler, too.

I imagine it would! You could rob a house and escape to the other side of the world right away. It would also be a great equalizer, as there would instantly be no borders. Countries would break down and lead to a single language before long. There would also probably be no sense of community, at least not based on where you live.

The Hyperion cantos has an exploration of a similar concept, if you are into sf. Although I can only truly recommend the first book, and to a lesser extent, the second.

Ah, it will probably interest me, thanks. I'll try the first book.

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.

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?

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.

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.

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

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.

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.

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

From Yonkers to Far Rockaway it's about 23 miles. From Mission Hills to Mission Viejo it's about 65 miles. LA is just a lot more spread out than NYC is, which makes public transit, especially such based on fixed infrastructure, that much more difficult.

Than again, I think one of the biggest costs for NYC public transportation is land costs. in LA, those would be a lot less.

NYC public transit was largely built (by private companies) a long time ago, when land was cheaper. Even the newer parts largely re-use existing ROW.

LA land how is more expensive than NYC land was then, even relative to inflation.

LA once had extensive rail lines--they were eventually bought by bus companies and turned into highways.

http://www.pbs.org/wnet/blueprintamerica/reports/america-in-...

http://articles.latimes.com/2003/mar/23/local/me-then23

The density of LA is still far too low for a NY style subway to be cost effective. Metro Rail is in some ways pseudo-inter-city-commuter-rail, similar to BART and the DC "Metro". Its also interesting due to its diverse type of trackae (heavy and light rail).

The density of the LA metro area is slightly higher than that of the NYC metro area.

The problem is vision: namely nobody has any. The folks who built NYC at the turn of the century had vision. They didn't just put in subway lines, they put in mostly four-track subway lines with room for express trains. They didn't just build commuter rail, they built a vast system (again with a lot of four-track to accommodate express trains) with stations in numerous little Westchester and Long Island town. Oh, and it was electrified in 1903 (kudos to Tesla, but all-electric commuting is very turn of the 20th century stuff).

Over 100 years later, we're still using that infrastructure. Today, of the 1.6 million people that enter Manhattan every day for work, 80% ride either commuter rail or the subway. This is a movement of people that would absolutely crush any other city despite their extensive highway networks, but New York handles it very well using ancient infrastructure.

FYI: all this visionary track was built largely by...wait for it...for-profit companies running competing tracks. The city socialized the subway in 1940.

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

They just have to build it and they will come eventually. Things will get denser near rail stops. The traffic situation is just not sustainable in LA and it's kind of pathetic. It takes time and it takes subsidization. Two things US democracies don't play well with.

they're working on it, with success.

http://en.wikipedia.org/wiki/Expo_Line_(Los_Angeles_Metro)

once this is running @ 100% (currently it's at 50% operation) for a couple of years there will be a major change in mindset on the west side and the wilshire line (subway to the sea) will be accelerated.

or at least i hope so.

Don't need rail, just rapid bus transit like Bogota. Have folks pre-pay so loading is snick-snick and give them an enforced lane to themselves.

Bogota does it right, here. NYC is starting to follow a bit with the Select bus lines, as well.

I'm really just shocked that all this time LA didn't synchronise their lights. What have they been doing?! NYC has scientists tuning our lights for a living, and cars aren't our thing.

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?

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

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.

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

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..."

OK sure, for all of NSW it's 3700+ intersections [1] (for a state with about half the population of LA), and 11000 across Australia [2] (about double the population of LA) with the same technology.

I can't find any reference that mentions every single intersection being hooked up, so I'll cede that one.

A very large grid might be a pathological case where it makes sense to hook up every single intersection, but in terms of scale, it is not unique or ahead of it's time, like the SCATS system was.

[1] http://www.rta.nsw.gov.au/usingroads/scats/index.html [2] http://en.wikipedia.org/wiki/Scats

I think it's just a case of the journalist defining the category to assure the subject of the story would be the sole qualifier.

Thanks for the intro links to SCATS. I hadn't known about it.

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.

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.

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

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

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.

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.

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