Speed Limit

​Share this page​

​Will a Lower Speed Limit Help Reduce Speeding?

A common myth ...

...Installing a lower speed limit will cause drivers to slow down and reduce accidents.

Facts indicate otherwise. Research conducted throughout the country over several decades has shown that drivers are influenced by the type of street and the current traffic conditions, and not the posted speed limit. 

When a speed limit sign is not posted, Arizona's Basic Speed Law (ARS 28-701) still applies. It requires that a person drive at a speed that is reasonable and prudent under existing conditions. In every event, speed must be so controlled as to avoid colliding with any object, person, or vehicle on the highway. It is the duty of ALL persons to exercise reasonable care for the protection of others.

Under Arizona law, the maximum speed limit...      

...in Phoenix is 55 miles per hour (mph). Other maximum speed limits established by law include the 25 mph limit on local streets in residential areas and business districts, and the 15 mph limit in alleys. Even though these speeds are not always posted, all motorists are required to know the basic speed laws.

Speed limits between 25 and 55 mph may be established on the basis of traffic engineering studies. These studies include roadway conditions, accident records and the prevailing speed of prudent drivers.

If an unreasonably low speed is posted, most drivers will ignore the signs, while a few may try to stay within the posted speed limit. This causes real safety concerns because of the difference between faster and slower drivers.

Setting unrealistically low speed limits...

... has two adverse effects.

  • They make violators out of reasonable and otherwise law-abiding citizens.

  • Most importantly, police enforcement is diminished, which plays a vital role in controlling the speed limit. Unrealistic speed limits create a difficult situation for the police and the community and citations are not upheld in court. Often the police will not return to the site to reinforce the law.

Speed limits approaching yellow school crosswalks are 15 mph when the portable signs are placed on the street. These zones may only be established based on traffic engineering studies and used only for children going to and from school, when school is in session (ARS 28-797).

Remember, unreasonably low speed limits




A traffic safety message from the Phoenix Street Transportation Department. For more information, call: 602-262-6235 TDD 602-534-5500