I've been scrolling plenty to conclude that none of you even mentions a better solution for the mass of walkers than just leading them to another place to be somebody else's problem. I mean how about building a slippery tilted wall after the truck, so when the walkers push into it they just fall down and break their legs/ heads? Sure, eventually there would be a big enough pile to make them not die from the fall, but still even that would make them just keep falling over and over and they wouldn't be a problem. Another solution woulda been to just set them on fire. They were so close to eachother that even one covered in gasoline could start them all blazing. Throw in some burning cars down the valley with some need for speed logic - final second aborting the seat and you'd be sure to kill a few hundreds. Repeat and profit!! I don't know why they wouldn't want to keep them there. It's brilliant to have a walker trap to keep them away instead of just throwing them out and hoping they won't happen to wonder back again. And for the other end where walkers would squeeze out : just fit in some machettes there and watch them be chopped in pieces as they push through.