Speed limit signs, maximum speed limits that is, are seen all over town, in the city, and in the country. Some types of roads have “statutory” maximum speed limits, and the limit signs need not be posted; for example residential areas have a statutory limit of 25mph.
The sign simply says “SPEED LIMIT” along with the number which must be in multiples of 5mph (due to MUTCD). The speed limit establishes the maximum speed at which a driver is considered to be driving at a reasonable and prudent speed; though slower speeds than posted may be required, depending on conditions. Anything above that speed is considered to be prima facia evidence of speeding. Arizona’s speed law is §28-701A and is often referred to generically as the “basic speed law”. Violation of this law if often called “SPEED GREATER THAN REASONABLE AND PRUDENT”, or, particularly in the event of a collision may alternately be referred to as “FAILURE TO CONTROL SPEED”, both referring to the same statute:
28-701. Reasonable and prudent speed; prima facie evidence; exceptions
A. A person shall not drive a vehicle on a highway at a speed greater than is reasonable and prudent under the circumstances, conditions and actual and potential hazards then existing. A person shall control the speed of a vehicle as necessary to avoid colliding with any object, person, vehicle or other conveyance on, entering or adjacent to the highway in compliance with legal requirements and the duty of all persons to exercise reasonable care for the protection of others.
Minimum Speed Limits
Minimum speed limits may be established “where engineering judgment determines that slow speeds on a highway might impede the normal and reasonable movement of traffic” (MUTCD, though the Arizona law is even more stringent). Where so established, they are signed with a placard, that is they must be used in conjunction with a maximum speed limit sign, not alone (there is also a combo sign). Here is the statute which supports minimums:
§28-704B. Minimum speed limits… If the director or local authorities within their respective jurisdictions determine on the basis of an engineering and traffic investigation that slow speeds on any part of a highway consistently impede the normal and reasonable movement of traffic, the director or local authority may determine and declare a minimum speed limit below which a person shall not drive a vehicle except when necessary for safe operation or in compliance with law.
Posted minimum speeds are rare. There are NO KNOWN posted minimums on any street in Arizona other than perhaps on limited-access highways (which is also unusual; I don’t recall ever seeing any in the Phoenix metro area). See comment below regarding the State Highway System.
Why am I telling you this?
Because, appallingly, some police either intentionally (lie or tell falsehoods) or through poor training insist that maximums are minimums. Like this Flagstaff PD officer.
Are Bicyclists subject to posted minimums?
Nobody knows, it may be the case, e.g. this is a rule which “by their nature can have no application”. In which case it wouldn’t apply.
Happily, we don’t need to ever find out or test this because as mentioned above, there are no known streets anywhere in Arizona where bicyclists aren’t prohibited (or restricted. Meaning limited access highways) that have established minimums.
Besides bicycles, there are many classes of vehicle permitted on any street in Arizona with limitations as noted. These road users, and bicyclists, are sometimes going to be going slower than the “normal speed of traffic”. This is by design, and is the expected use of these roads. [content and examples moved to new article slow-by-nature ]
In Arizona, the highest maximum speed limit anywhere is 75mph. Also note that anything in excess of 85mph is not just a speeding ticket, but automatically becomes a crime; §28-701.02A. The highest posted limit anywhere in the US is 80mph, except for a small area in Texas with 85mph.
SIDEBAR: The way the automobile industry designs and markets cars... Tesla says its Tesla Model S P100D in Ludicrous mode (ludicrous is one step higher than insane mode -- this is according to Tesla) is among, if not *the*, fastest production car in the world in terms of acceleration. Its motors develop something like 762 horsepower. Its maximum speed, limited through software, is only 155mph. But maybe this is just a one off? The Ford Mustang is available with "Four Engines. One Soul", according to Ford; offering from a low of 300 horsepower up to 526 horsepower. Some or all of them are limited to a top speed of 155mph. But it isn't just Ford, there's GM's Camaro and Corvette, and Chrysler's Charger. But it isn't just "muscle" cars, innocuous sedans, the Accords, Camrys, Taurus all sport multi-hundred horsepower engines and are capable of extra-legal speed (2016 Camry 2.6L SE "Top speed -- governor limited -- 112 mph")
Index of Arizona speed laws
For reference, here are all the laws in ARS chapter 28 relating to speed:
|Article 6||Speed Restrictions|
|28-701||Reasonable and prudent speed; prima facie evidence; exceptions|
|28-701.02||Excessive speeds; classification|
|28-702||State highway speed limits|
|28-702.01||Urbanized areas; waste of a finite resource; civil penalties|
|28-702.03||Maximum speed limit violation on interstate highway system in another state; effect|
|28-702.04||Maximum speed limit on interstate highways outside urbanized areas; definition|
|28-703||Alteration of speed limits by local authority|
|28-703.01||End of speed zone; signs required|
|28-703.02||Establishing speed on multiple lane highways|
|28-704||Minimum speed limits; requirement to turn off roadway|
|28-705||Special speed limitation; motor driven cycles|
|28-706||Special speed limitations|
|28-707||Charging speed violation; burden of proof; findings|
|28-708||Racing on highways; classification; exception; definitions|
|28-709||Maximum speed limit for large vehicles and vehicles with trailers|
|28-710||State highway work zone safety; civil penalty; fund|