Sure more lives are at stake, but I think the probability of physical harm to them is pretty low because
a) The bridge has been hit tons of times, and I don't think anyone in a train has been hurt yet.
b) The bridge is probably a lot stronger than the truck, so while the bridge may take damage and need to be repaired, the damage is probably not enough to harm train traffic.
c) If the bridge is damaged enough to harm train traffic, there's probably not a train coming immediately; any on-route trains can be likely stopped before they reach the bridge.
