A collar die clash is when the die accidentally strikes the collar die and this imparts an indent into the edge of the die. When this die strikes a coin it imparts this indent into the edge of the coin. If the coin has no reeding like a nickel or a cent then it looks like a double rim, if the collar die had reeding like a quarter or a dime then it looks similar to rail road tracks on the edge of the coin. Hence the nickname, "Rail Road Rim" for this particular error.
Collar dir clash is not to be confused with Finning. Finning is when the die is tilted or the coin is not properly seated and it causes greater striking pressure of the edge that moves metal up and above the rim. This creates a flange or double rim apperance but on reeded coins it has no reeding or railroad appearance since there's not die clashing.
People call dimes, quarters, half dollars and large dollars "Railroad" rims when they're clashed collar strikes and some of he edge reeding is struck out of place. It's not uncommon to find this with modern dimes and unless dramatic it doesn't add much if any value, and that includes the quarters and half dollars, but the larger the denomination the more valuable this will get.