Highways let you move fast only as long as they're intact and no one is shooting at you; otherwise, they make you an easy target. Russian army experienced that first-hand in the first two months of their invasion of Ukraine.
my point was that they tried and they failed. wagner has a bunch of manpads and few pantsir sam systems. they tried to bomb them on highway from planes but missed and kill civilians in track. they also tried to shoot at them missles at voronezh but blew up some petrol refinary. they also tried to bomb some bridge to block road to moscow - but also missed
No, I believe the oil refinery got blown up by a Wagner surface to air missile. The Wagners were trying to shoot down a federal Ka-52, the helicopter successfully deployed countermeasures, and the missile flew off target into the backstop - which happened to be a refinery.
There are two videos of the event from different angles circulating on telegram, it's pretty clear.