Here's a riddle for you: What's green and yellow, but most often red?

...Give up? It's a traffic light -- you know, those things you hit on your way into the office each morning. 

But how do they work? And why don't they ever seem to be synched up? 

This hour, we explore the science behind traffic light programming. We hear from engineers and experts in Connecticut and Utah. We also find out how new "smart" signals are improving traffic flow in Pittsburgh, Pennsylvania. 

Support the show: http://wnpr.org/donate

See omnystudio.com/listener for privacy information.