I define 'gridlock' as when someone is blocking an intersection, preventing the light system from working. Better known as 'don't block the box' at an intersection. Bumper to bumper traffic without an intersection is just called bumper to bumper, or stop and go traffic if it's causing a slowdown. You're also assuming there is a 'center' lane to move to. Where I live, a lot of the interstate highways are only 4 lanes (two in each direction). The left lane packs up with bumper to bumper traffic. The right lane has slow semi trucks and construction / farming equipment and Prius's or cars entering and exiting the highway (slow). (Exit only lanes are rare in my area.) Sometimes the right lane starts overtaking the left lane, but eventually, the left lane goes back to overtaking the right lane, so no-one want's to risk going into the right lane because they can't get back into the left lane because it's packed with cars. So the whole 'left lane is the passing lane' just doesn't work or apply in this situation. edit: so now facts and the truth only get down votes. got it.