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LA In Sync: Traffic Signals To Cut Travel Times

losangeles.cbslocal.com

31–40 of 47 posts

Re: LA In Sync: Traffic Signals To Cut Travel Times

#31

Earlier quoted context omitted.

When you say "other forward looking cities" I say "every city in existence". Seriously, why isn't EVERYONE doing this?

We have had this in Houston, TX for nearly a decade. They work pretty great if everyone is driving at the speed they're designed for. Otherwise you have to deal with red light runners, people parked at green lights texting, metro bus drivers parking their buses on the road while they go on break, people speeding and getting to the lights too early and people driving too slow. That said at off hours they're absolutely…

I love it when they're actually in-sync. I'm not sure of the cause, but they always seem to de-sync after a period of time. I remember we used to have a set speed, I think it was 26mph or so, that if you held, you'd cut right through downtown if someone didn't get in your way.

I'm with you on the surface streets, 45 at the Pierce Elevated (and 10 feeding into it) is its own little hell.

Re: LA In Sync: Traffic Signals To Cut Travel Times

#32

So kinda like this: http://en.wikipedia.org/wiki/Green_wave ?

Fascinating quote from the Wikipedia page: "In the UK, in 2009, it was revealed that the Department for Transport had previously discouraged green waves as they reduced fuel usage, and thus less revenue was raised from fuel taxes" :)

I wonder if any of the planners have been thinking the same way about this project.

EDIT: let me guess.

Burn 1 US gallon of petrol = 17.68 US pounds of CO2 (see http://www.eia.gov/tools/faqs/faq.cfm?id=307&t=11) = 8.02 kg. 1,000,000 tonnes is 1,000,000,000 kg, so 124,688,279 US gallons of petrol (so 471,996,258 litres, or 3m barrels, or something like 0.04% of all US annual consumption).

The California petrol tax per US gallon is $0.36 (http://www.boe.ca.gov/sptaxprog/spftdrates.htm), so this amounts to $44m. (Don't forget my calculations are quick and dirty.) So that's hardly nothing, but compared to the rest of the budget, a mere drop in the ocean, and probably worth doing if it speeds traffic flow and if reduced spew of noxious poisons and greenhouse gases is a policy goal.

(The same calculation run across the whole of the UK would probably produce more compelling numbers, suggesting that the green wave is a poor idea for the government - but reduction in greenhouse gases is a current policy.)

Re: LA In Sync: Traffic Signals To Cut Travel Times

#33
post #32

So kinda like this: http://en.wikipedia.org/wiki/Green_wave ?

Fascinating quote from the Wikipedia page: "In the UK, in 2009, it was revealed that the Department for Transport had previously discouraged green waves as they reduced fuel usage, and thus less revenue was raised from fuel taxes" :) I wonder if any of the planners have been thinking the same way about this project. EDIT: let me guess. Burn 1 US gallon of petrol = 17.68 US pounds of CO2 (see http://www.eia.gov/tools/…

[deleted]

Re: LA In Sync: Traffic Signals To Cut Travel Times

#34

Something that puzzled me when I came to the US was that traffic lights (including a majority of pedestrian lights) just cycles through a certain schedule. Where I come from, traffic lights have sensors in the ground that manages the traffic. Also, all pedestrian crossings have very responsive buttons that truly work. The crossing light won't come on unless someone presses the button. In the US, I can rarely tell if…

Spent a bit of time playing with traffic and parking. One of the issues with the dominant traffic sensor tech (inductive loops in the ground) is that they can fail in cold weather: frost heaves in pavement sometimes crack the loop wires.

In the south, southwest and the pacific northwest the incidence of loops is much higher than in the northeast. There's also more driving, so the incentive to optimize that part of the experience is much higher than say, in the Boston area, where they really just want you to give up the car and use public transportation.

Re: LA In Sync: Traffic Signals To Cut Travel Times

#35

I read the comments on the site and have pretty much lost my will to live. What a cornucopia of ignorance. Who let these people on to the Internet?

Nothing you wouldn't see at the appropriately named Yahoo News. Perhaps you can still read similar comments there.

Re: LA In Sync: Traffic Signals To Cut Travel Times

#36

"L.A. is about to become the first major city in the world to synchronize all of its traffic signals." For such an obvious way to improve traffic, safety and reduce pollution, it seems very odd that this hasn't been done before in other forward looking cities.

When you say "other forward looking cities" I say "every city in existence". Seriously, why isn't EVERYONE doing this?

I did my college senior design on this.

To put things in perspective, the city of San Jose, CA is currently doing a similar upgrade to the city's traffic signals and controllers at a cost of ~25 million dollars. While it is expected to save money in the long run, that's a serious chunk of change. The project (as government contract jobs tend to do) has also gone several years past its due date.

Re: LA In Sync: Traffic Signals To Cut Travel Times

#37
post #21

I live in LA, and today I honestly noticed a significant reduction in my commute time (from 45min down to about 30min), but this is the first I've heard of this. I thought I was just hitting all the lights, but interesting to find out it may become a more common occurrence! Looking forward to gathering more experience with the system.

How many miles is your commute?

A little over 9 miles, all surface streets. Marina del Rey to Beverly Hills. For what it's worth, I canvased about five people today and asked them the untainted question "Did you notice anything about your commute today?" and all of them said it was notably faster than usual.

Re: LA In Sync: Traffic Signals To Cut Travel Times

#38
post #21

Earlier quoted context omitted.

How many miles is your commute?

A little over 9 miles, all surface streets. Marina del Rey to Beverly Hills. For what it's worth, I canvased about five people today and asked them the untainted question "Did you notice anything about your commute today?" and all of them said it was notably faster than usual.

Hmm. Do you actually travel in the city of Los Angeles on that trip?

Re: LA In Sync: Traffic Signals To Cut Travel Times

#39
I'm a little surprised to learn the city of Los Angeles only has 4400 traffic signals. Though I've never tried to estimate the number.

I do remember reading only a small percentage of lights have a left turn arrow. Even major intersections can be missing them. Hence the LA unofficial practice of "two cars can turn left just as the caution expires". It's the only way you'd get through some intersections at all.

Re: LA In Sync: Traffic Signals To Cut Travel Times

#40
It's actually a fascinating problem. Naively, it seems you can't sync traffic in both directions of a 2-way street at the same time -- e.g. eastbound and westbound.

Two things I've thought of that would work for both directions:

1) if it's a square grid, you could pick some streets that are optimized westbound, and some eastbound, for example. And then carefully arrange those so the north-south streets also mesh with it.

2) if you can space the lights the right distance apart, you could create a "standing wave" where it is actually optimized both ways. But you'd have to space them farther apart and more regularly than in real cities. For example, you could set lights apart by 1 minute travel time at 30mph, if the signal cycle is 1 minute.

I'm curious what other solutions are to this, and how they do it in a place like LA in practice!

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