Rush-hour gridlock is as much fun as doing taxes. Especially peeving are those drivers who slide into the intersection before there’s room on the other side. “Don’t block the box,” say signs. But drivers do it anyway. Then the cars don’t move because of block-boxers at the next intersection, so everybody’s jammed. Here’s my solution: Sensors that change the light to red when the lane ahead is full. They calculate if the end car in each lane isn’t moving, and *red light* no more cars allowed here. As soon as the tail end clears, the light changes back to green. OK, detering scofflaws, that’s a problem. But if some people obey, traffic flow should improve. If not, more drastic measures, in escalating order: Add an LED sign that flashes “Don’t block the box” above the red light. Cameras at the intersection snapping license-plate numbers. Barriers that pop up, blocking folks from blocking the box. And treadles that’ll poke your tires out if you dare block the box. Of course, that’s not just over the top, it’s crazy: Giving a flouter four flats is no way to clear an intersection. Someday, it’ll all be computerized, with intelligent lights deciding which intersection needs to clear next, so the snarls make fewer drivers snarl.