Ever since freeways and (toll) turnpikes with grade separations were invented, there have been "bombings" from sidewalks. The solution was chain link fences the full lengths of the sidewalks; and sometimes the non-sidewalk sides. Suggest watching for them.

Bombing from overcrossings of railroads in the Northeastern United States was common starting with the invention of diesels with front or near-front cabs. The missiles were sometimes kitchen or laundry appliances. Most commuter units have prison-grade bars over the cab windows. More recently bullet-proof glass, such as a certain limousine. Some overpasses have guards during rush hours

Some crossings over railroads outside the Northeast may already be protected by chain link fencing. A lot more will be.

Railroads and highways in trenches are particularly vulnerable. The miscreants disappear much more quickly than on overcrossings.