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Comment by gojomo | Hacker News Reader

Rather than having the traffic lights sending invisible signals to special receivers, they could just have digital countdown timers, visible from a distance, on both red and green lights.

I've saw a bunch of these in China, but not yet in the USA. (The closest I've seen commonly in the USA are the countdown timers, instead of blinking lights, on more recent pedestrian crosswalk signals.)

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So audi spent who knows how much on a complicated solution - when there already is a perfectly workable simple one.

Reminds me of the pen vs pencil joke about nasa vs russia.

The countdown counters are about the same size as one of the lights whereas to be able to comfortably see the counter from a moving vehicle from at least 100 meters, the numbers on the counter should be humongous. After all, the main idea behind this is knowing beforehand (long enough beforehand) what the light will turn into and when so that you can accelerate just enough to make it through just before the green ends, or decelerate enough to make it to the intersection just as the green comes on so that there's no need for braking, stopping and starting again.

I found them quite large and readable from long distances. Here's an image I found online of a countdown traffic light in Shenzhen, China:

http://bbeled.com/project/images/dongguan.JPG

And even Thailand:

http://bbeled.com/project/images/taiguo.JPG

Come on, USA, let's get with the 21st century already!

(Photos in context at http://bbeled.com/project.htm , click the second 'Traffic signal light' tab.)

Mandatory link about a space pen: http://www.snopes.com/business/genius/spacepen.asp

Yep, these are commonplace in India too. It seems like an easier & cheaper solution. Only thing is the government needs to invest in new lights. Audi got tired of lobbying/waiting, and took things into its own hands.

two questions:

1. at what distance can you see the time left?

2. this still does not solve for calculating the speed necessary (for which to utilize as a benchmark if you're actually going to make it through the light).

in pedestrian crosswalk signals, ability to accelerate is probably an order of magnitude greater -- you go from walking to running to beat the signal.

not so with traffic lights, even if you have a visible countdown timer (and as i mentioned above, how will a human calculate the baseline speed at which it is necessary to drive in order to be able to safely cross).

I hope that the ones for cars are actually accurate, unlike the pedestrian ones which drastically underestimate the time, causing people to ignore it completely and just look both ways.

All the pedestrian crosswalk countdowns I've seen seem to tick off true seconds, with perhaps one extra second at '0'.

Well... the seconds are appropriately long, there just aren't enough of them, so there's plenty of time left to cross after 0. Or maybe it's just Porter Square's weirdness, to go along with the striped sidewalks and windmill and boulders...

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