Every state has their own traffic laws. However, I think most states are very similar to California in this regard:
Basic Speed Law
California’s Basic Speed Law states that drivers must not exceed a safe speed based off road and weather conditions. This means that driving the speed limit may be considered too fast in relation to your environment. Important factors to pay attention to during your drive include:
General Traffic Flow. Is everyone going the speed limit or are other drivers slowing down because of rush hour or an accident nearby?
Weather. Is it raining or snowing, and you need to slow down for your safety? Or is it sunny with 100% visibility?
Number of Vehicles on the Road. Are there a lot of drivers around you? Is the 65 mph speed limit too fast in comparison to the traffic?
Pedestrians. Are there pedestrians or bicyclists near your lane? Can you switch lanes to give them more space and prioritize safety?
Road Surface. Are you driving on hills or flat surfaces? Are there speed bumps nearby?
Animal Signage. Are there warning signs for animals in the area? Should you be more cautious?
Construction Zones. Is there construction occurring on the freeway or a business district? Are there speed limit signs or detours to your destination?
Nearby Accidents or Cars Pulled Over. Are you on a two-lane road? Is it possible for you to merge over to the other lane?
If you are a commercial driver operating a towing vehicle, bus, or large truck, the Basic Speed Law applies to you as well. There are, however, a few extra conditions to ensure you are driving safely. With a larger vehicle, you should be driving in the right-most or second rightmost lane, depending on the number of lanes on the road or highway you are on. In addition, there is signage about reduced speed limits for commercial vehicles around the state serving as a precaution due to the extra weight your vehicle holds. Wherever you are driving, remember that your vehicle may create large gusts of wind that may impact cars or pedestrians around you.
Prima Facie Speed Law
The Prima Facie Speed Law mandates maximum speed limits in areas where speed limit signages may not be posted but should be known and followed. If you do not abide by this speed law, you are at risk for a citation. For instance, if you are on a street in a neighborhood with no posted speed limits and you are driving 30 mph, you are breaking Prima Facie.
In school zones, residential areas, and business districts, the Prima Facie speed limit is 25 mph. If there are marked signs that say otherwise, follow those. For instance, some school zones may regulate their speed to 15 mph. The basis of the Prima Facie Speed Law is to ensure everyone is driving at a safe speed based on the environment they are around even if there are no marked signs.
The Prima Facie speed for alleys and railroad crossings is 15 mph. This is of utmost importance if you are unable to see oncoming traffic or trains in both directions for 400 ft each side to prevent any harm and keep you safe.
Maximum Speed Law
The Maximum Speed Law may be the most known speed law in California. This law simply states that you cannot exceed the posted speed limit, which applies when you are trying to pass slow drivers. You may not exceed the speed limit or ‘go with the traffic flow’ because it puts others at risk for potential harm.
A common myth with this law is that officers use speed traps to patrol driver’s speeds. A speed trap is a practice where you calculate the time in between each checkpoint and determine the speed the driver was going between the two. With this process, if you were speeding in between the two, you would get a ticket. Speed traps are not legal in the state of California. This does not give individuals a right to speed, however; radar devices are still legal and if caught speeding, you receive a citation.
Minimum Speed Law
Contrary to what some may believe, it is possible to get a citation for driving too slowly. California’s Minimum Speed Law prohibits that drivers be too slow, as this interrupts traffic flow and poses a threat to other drivers. Though it is not common, there are some minimum speed limits posted throughout the state.
Regarding the Basic Speed Law, it is okay to reduce your speed while driving; it is significant reductions that create potential danger. Consider the environmental factors that may impact your speed and remember to always utilize safe driving practices.