It's not just safety concerns in general (though it could be in DC): the other problem is that road damage is approximately proportional to the fourth power of

It's not just safety concerns in general (though it could be in DC): the other problem is that road damage is approximately proportional to the fourth power of axle weight. So doubling the weight of a car causes 16 times the road wear. And a car twice the size takes up twice as much road room and parking area too. So there are externalities with bigger vehicles that are beyond that of mangled pedestrians and which their owners could reasonably be required to pay for. Of course, these are even more true of large trucks, which we would find much more difficult to eliminate, even if we wanted to. So it's always going to be a matter of judgement how to proceed.