Speed limits are restrictions on the minimum and maximum speeds vehicles may travel on a given stretch of road. Speed limits are designated by signs and are used in many countries. In the United States, speed limits are used to protect drivers and regulate unruly or dangerous behavior on the roads.
There is no guarantee that posting speed limits has any effect on driver behaviors, as most drivers will ultimately travel at the speed that they feel the most comfortable going. However, law enforcement does monitor the speed of motorists and failure to adhere to posted speed limits can result in fines and, depending on how fast a driver is going, arrest.
Speed limits vary between states and are often different for rural interstates, urban interstates, and other types of roads. Montana has different speed limits for day and night on certain types of roads. Some states, such as California and Arkansas, have different speed limits for trucks and cars.
There are three main categories of roads: arterial, collector and local. Arterial roads have higher speeds and fewer access points, such as on- and off-ramps. Collector roads have high speeds and are balanced to have more access points. Local roads have lower speeds and more access points, such as intersections and cross streets. The difference between these three types of streets is the reason why there are different speed limits. Roads with fewer travelers and fewer vehicles attempting to cross one another can sustain higher speeds, while roads with more volume of travelers and have more bikers or pedestrians need to have lower speeds.
South Dakota has the highest speed limits in the United States. Rural and urban interstates both have a speed limit of 80 miles per hour and other roads are posted at 70 miles per hour. Hawaii has the overall lowest speed limits in the United States. Rural and urban interstates in Hawaii have a speed limit of 60 miles per hour and other roads are posted at 45 miles per hour.