This gives a good insight of the hazards with an emergency landing on a highway.
If the wide straight road makes it very convenient, you have plenty of bridges, little visible powerlines crossing the highway, lights, road signs...
But above all, and despite of a rather medium density of traffic, people in cars are totally unconscious of what's happening and what could have happened after touchdown.
First of all, the guy who is filming is far enough to have spotted the aircraft quite early, but the plane has probably been out of the field of view for most drivers ahead until abruptly dropping from the sky and touching down, while the pilot has nearly zero view of cars below or behind him.
Then, no ones seems to give a sh...t, they don't even slow down or try to get out of the path despite a wingtip could have collided anything or a gear leg collapse or whatever causing a sudden loss of control of the aircraft. Instead you could almost hear some of them yell "hey ! don't land right in front of me! I was first, get out of my path you %&*@!!!"
They only brake when forced to, make a hook to pass the aircraft and resume their cruise without wondering if anyone might need assistance.