Seeing that using vehicles to commit mass murder, I have an idea:
Plant poles and posts between sidewalks and streets. These need only be in places where high pedestrian traffic is likely.
They should be placed so that a vehicle travelling at high speed could not negotiate between them, They could be
wooden telephone poles or weak-looking posts constructed of solid steel and implanted in about five feet of concrete.
They could also be placed in front of entrances to buildings, Pedestrians and delivery vehicles could easily avoid them,
but not high-speed attack vehicles.