Why shut down the interstate that has a lot of truckers, interstate commerce, people travelling through?

The vast, vast majority of mourners are the local citizens. Shut down local roads, allow people to line both sides to pay respects in a safer manner. Let' the trucker doing his job and trying to get from Los Angeles to Boise do his job. Rather than slowing them down and forcing them to get off and detour through a place they aren't familiar with?