One of the most basic, though frequently violated, rules of the road is the speed limit. Speed limits are intended to protect drivers and pedestrians from accidents that can occur when a car is driving too fast for conditions. While following a speed limit is usually straightforward, there are more complicated situations where speed limit signs need to be read carefully.
Most states have a maximum speed limit that applies to all state roads. This does not mean the maximum speed limit is always legal, nor does it mean that it is never legal to drive faster than this speed. Rather, it is the speed limit that applies on roads that are unmarked and may play a part in insurance rates or highway safety regulations. Most states have a state speed limit between 65 and 75 miles per hour; these are the speed limits posted on open highways.
Certain roads have especially low speed limits, which may be posted along with the reason for the lower speed. School zones and hospitals are places where drivers are required to reduce their speed. In the case of school zones, speed limit signs will indicate whether the lower speed limit must be observed only on school days, only between certain hours of the day or only when children are actually present. Likewise, residential neighborhoods where pedestrians are common may have speed limits of 45, 35 or even 25 miles per hour. Some parking lots may also have speed limits as low as 5 or 10 miles per hour.
Speed limits are almost always lowered in work zones. This is done in the interest of the safety of the workers and to prevent drivers from speeding through an area where rough roads, lane shifts or debris in the road may create dangerous conditions. Work zones on a highway may have signs indicating a speed limit of 55 or 45 miles per hour. On other roads, work zones may simply be marked with signs that read "slow" requiring drivers to exercise discretion based on the specific conditions. For violating speed limits in a work zone, fines are often increased.
In some cases, different speed limits will be posted on the same road. This is most common on highways. Speed limit signs sometimes require trucks, or cars towing trailers, to adhere to a lower speed limit or use a special truck lane. Also, some roads will be marked with a lower speed limit that drivers of trucks must follow at night when visibility is reduced. Reading such signs carefully is essential to understanding which speed limit applies.
There are some cases where speed limits are enforced without being posted on roadside signs. Some cities of neighborhoods require a special speed limit in all residential areas. Such speed limits may be posted at the entrance to a gated community or neighborhood, but not posted on each individual road. In addition, special locations such as intersections or railroad crossings often have speed limits or 15 miles per hour, which drivers are required to be aware of even if the speed limit itself is not posted. Most states also explicitly require drivers to slow down under special circumstances, such as extreme weather, when the legal speed limit may become a practical safe speed rather than the maximum speed that is posted.
