February 13, 2010
Hacking Traffic Signals
I noticed something funny on my walk tonight. The traffic signals in Pullman are timed funny for pedestrians.
I've always lamented how horrible "downtown" Pullman is for pedestrian traffic. Smash a crosswalk button and you often have to wait for 5 minutes for the lights to change. Most of our intersections have traffic flow sensors on the signals (cheesy little things, I honestly have no idea how they work). I sat at one intersection and tried a few experiments to see how the traffic flow affected crosswalk time.
Experiment 1: Hit the button while traffic is flowing steadily through the intersection. Time to light change (and my 'walk' sign lighting up): 3:30.
Experiment 2: Hit the button while one car is going through the intersection. Little to no traffic following this car (two more cars went through the entire time I waited for this change): 3:30.
Experiment 3: Hit the button while no traffic was flowing through the intersection. There was a ten second gap in traffic. The light changed in 0:15.
Conclusion: The traffic algorithm at this particular intersection is retarded. It must measure traffic flow at the moment the 'walk' button is hit, and decide how long to wait based on that single measurement. As a pedestrian, you should wait until there is a small break in traffic to hit the walk button. You'll probably save time by not hitting the crosswalk button right away...
Given your little experiment I suspect the developers were either stupid, cheap or both. We had to do the hardware timing for asynchronous traffic control, it's a pain, it also requires a more expensive chip. The lazy way is to just wait for the cycle to finish if it detects a car then inject a walk cycle.
Posted by: steve k on March 4, 2010 06:06 AMPost a comment
Further back...
ArchivesFriends and Family
Search
Previous Trips...
-
Hiking Mount Whitney, 2007 
Spring Break in West Virginia, 2005
New Year's in Paris, 2003-2004
Coming to America, 2003
Protesting in Berlin, 2003
Prague Bier-Tour, 2002
Dresden, 2002
Recent Reading
![]()
Stealing the Network
I first bumped into the Stealing the Network series when reading the exploits of Joe Grand, one of the book's many hacker authors.
The 'Stealing the ...' series of books follows a rather disparate group of computer hackers as they help a former NSA spook (many of them unwittingly) gather the money he needs to retire.
The stories themselves are not fantastic fiction. The writing is uneven and choppy, the characters are stereotypical and not very well thought-out. What is fascinating about this book series is the technical accuracy of the exploits (at some points *too* accurate, with screen shots and step-by-step instructions).
It's a great series to read if you're a system administrator, or just getting into the wonderful field of computer security.
Rated 
by reid
on March 06, 2011
by reid
on March 06, 2011
![]()
Close to the Machine
Ellen Ullman is one of those authors that somehow avoided my radar. Until now...
Close to the Machine is less a book than a collection of loosely related personal anecdotes from Ellen's time as a very rare thing -- a successful female bisexual independent computer programming consultant.
In the course of her work and relationship life, she learns hard lessons about programming, running a business, being lonely, and loving the wrong people. I found it particularly poignant being a crypto-nerd with difficult times in relationships and a more-or-less NDA'd, secret work life.
This book is a must-read for anyone into running their own business, programming, or anyone dating a person that is a business-a-holic or programmer.
Rated 
by reid
on November 23, 2009
by reid
on November 23, 2009
![]()
The Long Trip Home
I had the joy of dining with the author in Florida. We went to a little Brazilian BBQ where he spoke with our waitstaff in (what I can only assume was) flawless Portugese.
Brian Wyllie spent 1969-1971 living in Brazil working for the Peace Corps. His recent book outlines his trip back to the United States via Bolivia, Peru, and the Carribean chain, by way of bus, train, and sailboat. The format comes spattered with observations from the modern day, and makes me think, "this must be what John McPhee's journal looks like."
The trip sounded like a fantastic one, but I was left wanting more detail...where did the gun (being snuck through customs in a variety of places, no doubt) come from? And how did Geneve's hair smell? Alas, we'll have to wait for another book to find the answers.
Rated by reid
on April 16, 2009
by reid
on April 16, 2009
Time to get out of Pullman, for your sanity!
Posted by: Erik on February 14, 2010 04:55 AM