Speed limits in the United States are set by each state or territory. Highway speed limits can range from an urban low of 35 mph (56 km / h) to a rural high of 85 mph (137 km / h). Speed limits are typically posted in increments of five miles per hour (8 km / h). Some states have lower limits for trucks and at night, and occasionally there are minimum speed limits. Most speed limits are set by state or local statute, although each state allows various subdivisions (counties and municipalities) to set a different, generally lower, limit.
who sets the reasonable safe speed limit on any roadway
each state or territory