SMV emblem

Identification of Slow Moving Vehicles

It sounds like a word problem straight out of a math textbook: If a car is traveling 60 mph and approaching a tractor traveling 20 mph, how long does it take for the car to travel 400-foot and reach the tractor?
The answer is less than 6.5 seconds; not a lot of time for the driver of the car to slow down, unless there is sufficient warning. The slow-moving vehicle (SMV) emblem, a fluorescent orange triangle with "retroreflective" borders, does just that. It warns approaching motorists to slow down.

The SMV emblem is required by the Ohio Revised Code when moving "implements of husbandry" and farm machinery on public roadways. Implements of husbandry are vehicles designed and adapted exclusively for agricultural, horticultural, or livestock-raising operations. Additionally, SMV emblems are required on other specific vehicles, including horse-drawn vehicles.

SMV Characteristics
  • Must meet ASABE standards: Look for highest ‘dot #’ on the “ANSI/ASAE S276.#” label when purchasing an SMV emblem. For example, a S276.7 would be preferred over an S276.3
  • Visible 500-feet to the rear; readily identifiable both day and night
  • Condition of the emblem: clean, undamaged, not faded. SMV’s fade over time and need to be replaced periodically
SMV Emblem Mounting
  • Visible to the rear
  • Triangle point facing upward
  • 10 degrees from vertical
  • 2 to 10 feet above the ground
  • In center of vehicle or as near left-center as practicable
  • Securely or rigidly attached (not required to be permanently mounted)
Restrictions on SMV Use

MAXIMUM vehicle speed = 25 mph
Emblem not to be used when transporting equipment with motor vehicles such as on a truck or trailer or at speeds greater than 25 mph; the SMV should be removed or covered when being hauled.

Emblem is not to be used on stationary objects such as fence posts, gates, etc.

It is common to see the SMV emblem hanging on mailboxes or fences as a roadway marker. The International Society for Agricultural Safety and Health (ISASH) has drafted a letter encouraging SMV manufacturers to place a removable label stating the intended use of the SMV (to identify Slow Moving Vehicles). Please encourage your neighbors to use other reflective devices and preserve the heritage of this rural icon for roadway use as it was intended.

High Speed Tractors Traveling Faster Than 25 mph

The scope of the Speed Identification Symbol (SIS) standard is primarily to identify farm machinery traveling at ground speeds greater than 25 mph.  The SIS also identifies the farm machineries’ maximum speeds. The SIS needs to be visible 300-ft-100-ft to the rear, used in conjunction with the SMV emblem and comply with ASABE standards. These emblems are reserved for machinery meeting the definition of “High Speed tractors” as declared by the manufacturer.

What does the SIS law change for Ohio farmers?
  • Allows farm machinery to operate above 25 mph when displaying both SMV and SIS emblems. Requires the operator to possess documentation of manufacturer’s stated maximum speed of the vehicle. The SIS of both the vehicle and the implement in tow may not exceed this documented speed
  • Requires the operator to possess a driver’s license to operate any equipment above 25 mph
Where can you get an SIS?

All SIS emblems must be ASABE approved.  For more information about obtaining an SIS, contact your implement dealer.


History of the SMV Emblem

In 2013, the SMV celebrates 50 years as a safety symbol to alert the motoring public when sharing the roads with agricultural equipment and horse-drawn vehicles.

In the late 1950s a 10-year retrospective study of fatal tractor accidents was conducted by Walter McClure and Ben Lamp, both of the Department of Agricultural Engineering at The Ohio State University (AEOSU), to understand the nature and causes of highway tractor collisions. The research indicated a significant number of fatalities related to highway travel of slow-moving vehicles (SMVs). A research proposal written by Ken Harkness (AEOSU) and funded through the Automotive Safety Foundation (1961-62) further focused understanding of SMV accidents and resulted in the development of a unique SMV emblem. Early data estimated that 65 percent of the motor vehicle accidents involving SMVs were rear-end collisions. The Ohio State Highway Patrol, county sheriffs, and municipal police cooperated in the research by gathering detailed data on 708 SMV accidents.

In 1962, under the supervision of Ken Harkness, the design and testing of the SMV emblem was completed. A 1/16 scale highway simulator had been constructed to test human recognition rates of different shapes and colors mounted on simulated SMVs. After testing various designs, a triangular-shaped emblem with a 12-inch-high fluorescent orange center and three 1 3/4 inch wide reflective borders was determined to be the most effective design for day and night visual identification.

The Goodyear Rubber and Tire Company sponsored initial public exposure to the SMV emblem in 1962. An emblem mounted on the back of a farm wagon and towed by a Ford Tractor made a 3,689 mile trip from Portland, Maine to San Diego, California.

The first formal introduction of the SMV emblem was at a University of Iowa Invitational Safety Seminar in 1962. Carlton Zink of Deere and Company then became an avid promoter of the SMV emblem and played a major role in the adoption of the emblem by the American Society of Agricultural Engineers (ASAE).

In 1963 Novice G. Fawcett, President of The Ohio State University, dedicated the SMV emblem to the public. Also in 1963 the Agricultural Engineering Journal printed its first article with color illustrations about the SMV emblem. The National Safety Council promoted the adoption of the emblem and awarded a Certificate of Commendation to Ken Harkness.

In less than two years from the emblem’s first date of availability, Nebraska, Michigan, Ohio, and Vermont adopted legislation requiring the emblem to be used on SMVs. Safety Leader Bill Stuckey, an Ohio Farm and Home Safety Committee member, spearheaded the adoption of the SMV emblem in Ohio. In 1967 the Canadian Standards Association (CSA) adopted the SMV emblem as a CSA Standard. In 1971 the SMV emblem became the first ASAE Standard to be adopted as a national standard by the American National Standards Institute (ANSI).

In recognition for the research and development of the SMV emblem, Ken Harkness was selected as a Charter Member of the Ohio Safety Hall of Fame in 1992.

In 1992 the American Society of Agricultural Engineers designated the development of the SMV emblem as an ASAE Historic Landmark.

In 2013 the SMV celebrates 50 years of existence in the United States. It has been adopted for use in other countries, and is currently undergoing review to receive designation as an International Safety Standard. The SMV is one of the most recognized emblems used by farmers and ranchers around the world. It is with great pride that Ohio can boast the development of this emblem by OSU faculty and students. For 50 years, this emblem has been behind agricultural equipment and horse-drawn vehicles warning the motoring public of a Slow Moving Vehicle.