I guess you didn't see the roadblock searches on Friday. In one lane, LE was stopping the car before any white van, to block it in. I kept thinking about the drivers of the cars in front, in back and on the sides of each van. If I were on one of those road-blocked highways, I'd be jockeying for position away from any white vehicles, since LE obviously hasn't considered your scenario.
Glade that you pointed this out. You have to remember that an LEO's primary responsibility is "Officer Safety". The vehicle in front is the LEO's cover...God help the driver caught in a firefight. If that driver tries to move his vehicle out of position, he will be jailed for refusing an offical order from a PO and possibly endangering a PO.