Definitely a contender for worst intersection in America, and possibly the best argument for mandating self-driving cars in cities.

My take is that it's a combination of engineering failure and user error.
- Engineering failure: During rush hour, the E-W green light on Trumbull & Orange (to get on the highway) allows cars in at a lower rate than they feed from Phelps Triangle (via Whitney/Temple/Trumbull), and Trumbull St at the southern end of the triangle (between the light at Temple and the light at Whitney) can only fit ~3 cars at a time without blocking either intersection, and anyone trying to make a lefthand turn from Trumbull onto southbound has the potential to hold up all westbound traffic at that choke point. Also, green-lit right turns from Whitney (northbound) onto Trumbull (eastbound) are set up to be inherently in conflict with pedestrian crossing, so when there's a high volume of both (e.g. around 5pm), drivers inevitably get frustrated.
- User error: Drivers trying to get home from work are like rabid dogs; some of them would rather take their chances at causing gridlock -- or what the hell, even hitting a pedestrian! -- then wait one more turn at one of those damn lights. Eastbound and westbound drivers are constantly trying to turn a 1-lane into a 2-lane to speed around or squeeze in. Northbound drivers start exhibiting aggressive and risky behavior when pedestrian crossings take up most of the green light they want to use to turn right onto Trumbull. Lots of drivers misjudge (or lie to themselves about) how much time they'll have to cross the intersection and whether traffic will start to move by the time they get across, causing frequent gridlock.