Speed limits and the basic speed law

By the end of this topic you can

• You can find and obey the posted speed limit on any road.
• You can explain the basic speed law and apply it in rain, fog or heavy traffic.
• You can slow down correctly in school zones and other reduced-speed areas.
• You can tell an advisory speed sign from a speed limit sign.
• You can keep pace with traffic without exceeding the limit.

What you need to know and understand

• Speed limits are set by each state, not by the federal government. Varies by state: check your state manual.
• The basic speed law applies on every road at all times, even below the posted limit.
• Many states set default limits that apply when no sign is posted. California uses 25 mph in business and residential districts; Oregon uses 25 mph in residential districts and 20 mph in business districts.
• School zone limits vary: California's is 25 mph within 500 feet of a school when children are present, while Oregon's is 20 mph.
• Yellow advisory speed signs on curves and ramps recommend a safe speed; black-on-white signs set the legal limit.
• Exceeding the limit to pass is still illegal.
• IIHS research shows a pedestrian's risk of serious injury or death rises sharply with impact speed.

Posted limits and default limits

A white rectangular SPEED LIMIT sign shows the maximum legal speed in mph under good conditions. Where no sign is posted, state law sets a default for that type of area, such as residential streets, business districts or rural highways. These defaults differ between states, so learn the ones in your state manual.

Some highways use electronic variable speed limit signs that change with weather or traffic. When they show a lower number, that is the limit.

The basic speed law in practice

Ask yourself whether you could stop safely within the distance you can see to be clear. If not, slow down. California's handbook suggests slowing by 5 to 10 mph on wet roads, cutting your speed in half on packed snow and driving no faster than 5 mph on ice.

• Rain, fog, snow or ice
• Darkness and glare
• Heavy traffic or many pedestrians and cyclists
• Narrow, winding or hilly roads
• Work zones and crash scenes

School zones and other low-speed areas

School zones are marked by a five-sided school sign, often with a reduced limit that applies at certain times or when children are present. Read the signs carefully: some use flashing lights, some list hours. In California the limit is 25 mph within 500 feet of a school while children are outside or crossing, and some zones are as low as 15 mph.

Other low limits are common near alleys, blind intersections and railroad crossings. California, for example, sets 15 mph for alleys and for blind intersections.

Common mistakes

• Treating the limit as a target in bad weather. Adjust to the conditions under the basic speed law.
• Speeding up to pass. Passing never makes speeding legal.
• Missing the end of a school zone sign or the hours it applies. Read every part of the sign.
• Confusing a yellow advisory speed with the legal limit. Advisory speeds are guidance for that curve or ramp.
• Creeping over the limit to match fast traffic. Keep to the limit and stay right if you are slower.

Test yourself: Speed limits and the basic speed law

Answer each question, then read the explanation. Questions come in a random order each time.

Go deeper

• Basic Speed Law and US Speed Limits
• NY School Bus Law and Move Over Law Explained
• North Carolina School Bus Stopping Law