Freight Truck Blocker Lot

[Kevin1a]

I know about the blocker lots that block everything except for buses.  I'm looking for freight truck blocking lots that let everything else through.  Basically I want to force the sims in my city to move the freight via rail or port.  By using the blocker lots on all roads out of the city, the shortest route, and the only remaining route for freight traffic will be through a freight station.  I ran some Google searches, but I'm having a hard time finding something like this.  Thanks to anyone who can point me in the right direction.