Traffic Safety Spotlight – Speed Limits FAQs

Speed limits are more than a number on a sign. Engineers and traffic investigators set them to promote safe, consistent travel, and they can vary based on roadway characteristics, traffic patterns, surrounding development, and other conditions.

Speed Limits are More than a Number

Our latest Traffic Safety Spotlight FAQs take a closer look at how speed limits are determined, why they may change along the same roadway, what the 85th percentile speed means, when speeding penalties increase, Florida’s “Super Speeder” law, and why drivers should always adjust their speed for current conditions.

What is the purpose of a speed limit?   

A speed limit (posted or unposted) establishes the maximum and/or minimum operating speed that is considered reasonably safe in optimum weather and visibility conditions, which a normally prudent driver can perceive and react safely to driving problems encountered on the roadway.

How are speed limits established?  

Florida Statutes require an engineering and traffic investigation to be conducted for any alteration of speed limits, mandated in Sections 316.187 and 316.189 F.S.  The FDOT Speed Zoning for Highways, Roads, and Streets in Florida manual includes guidelines and procedures for performing traffic engineering investigations related to speed zoning in addition to information on the philosophy of speed zoning and the identification of some of the factors to be considered in establishing realistic, safe, and effective speed zones to which meaningful enforcement can be applied.

What does the 85th percentile speed mean?   

The 85th percentile speed is the speed at or below which 85% of the observed free-flowing vehicles are traveling.  Studies have shown that the observed 85th percentile speed generally reflects the collective judgment of the vast majority of drivers as to a reasonable speed for given traffic and roadway conditions.

Will lowering the posted speed limit make speeding drivers slow down?   

Not necessarily. Changing the number on the sign alone may have little effect on actual travel speeds.  A combination of engineering changes, enforcement, and education may be necessary to influence driving behaviors.

Why does the speed limit change along the same roadway?  

Roadways may consist of varying developments, intersections, roadway geometry, traffic volumes, pedestrian activity, access points, and operating speed changes that differ from one segment to another, supporting the establishment of different speed limits along the same roadway.

Who sets speed limits on Florida roadways?   

The Florida Legislature authorizes the appropriate roadway agencies to establish speed zones. FDOT establishes speed limits on State Highways, while counties and municipalities establish speed limits on roads under their jurisdiction in accordance with Florida law.

How do I get a speed limit reviewed?   

Contact the agency responsible for the roadway and request a speed limit review. For FDOT roads, contact the District Traffic Operations Engineer at the local FDOT District Office. The agency can determine whether an engineering study or additional review is warranted.  For county/city roads, contact their Public Works or Engineering Departments.  The existing speed limit within a speed zone will not be changed if the 85th percentile speed or upper limit of the 10 mph pace is within +/- 3 mph of the posted speed limit, unless a supplemental investigation identifies the need for a change.

When are speeding fines higher or doubled?   

Florida law increases speeding penalties in certain locations and circumstances. Fines may be doubled in school zones, qualifying construction zones, and properly posted toll collection zones. Additional penalties may also apply in enhanced penalty zones and for certain repeat violations involving excessive speeds.

What is Florida’s new “Super Speeder” law? 

Florida law calls the offense dangerous excessive speeding. Driving 50 mph or more over the speed limit, or driving 100 mph or more in a manner that threatens the safety of people or property or interferes with another vehicle, can result in criminal penalties, including fines and possible jail time.

Do I have to slow down when weather or roadway conditions are bad?   

Yes. A posted speed limit identifies the maximum speed considered reasonably safe under favorable conditions. Drivers must reduce their speed when weather, roadway, traffic, pedestrian, or other conditions make the posted speed unsafe.