Riding mowers, lawn tractors, lawn and garden tractors and garden tractors are covered by several safety standards that are designed to protect you, the operator.
 
The standards for riding mowers and small tractors are industry consensus standards developed by engineers and safety specialists working for the manufacturers and universities. Manufacturers are not required to adopt or conform to these industry consensus standards, although most reputable companies will do so and will so certify. The United States Consumer Product Safety Commission has developed federal regulations for walk-behind mowers but not for riding mowers.

American Society of Agricultural and Biological Engineers (ASABE) -- formerly American Society of Agricultural Engineers (ASAE)
ASABE has several standards dealing with this type of equipment, although many elements of the ASABE standards cover issues other than safety. Standards issued by ASAE prior to the name change remain ASAE standards. ASAE S440.2, Safety for Powered Lawn and Garden Equipment, covers safety aspects of operators’ manuals, control locations and operation, operator’s station, servicing issues, stability on slopes, shields and warnings, and braking requirements. Other ASABE standards cover the design of drawbars, 3-point hitches, sleeve hitches, hydraulics and PTOs. Safety factors specific to each of these areas are covered in the appropriate standard.

American National Standards Institute (ANSI)
ANSI standard B71.1, Walk-Behind Mowers and Ride-On Machines With Mowers - Safety Specifications, is the primary safety standard for homeowner riding mowers and small tractors. This standard requires the use of an operator presence control, a device that will stop the mower blades if the operator leaves the seat without disengaging the blade drive (PTO). This prevents an operator from being down on the ground around a mower while it is running.
 
One of the most important features of this standard is a requirement that the blades must stop turning within 5 seconds when the PTO is disengaged or the operator leaves the seat. This requires an automatic brake on the blade drive. ANSI also requires that mowers be tested to strict performance standards for thrown objects.
 
A seatback height of at least 4½ inches is required to keep operators from falling backward. There are requirements on dynamic turn and sudden traction performance to improve machine stability. There are requirements for braking performance. There are also requirements on guarding and safety labeling. The blade tip speed is limited to 19,000 feet per minute.

Outdoor Power Equipment Institute (OPEI)
OPEI is a trade organization whose member companies manufacture more than 95 percent of the power lawn and garden equipment on the market. Although OPEI is not a standards-issuing organization, OPEI led in the development of ANSI B71.1, and equipment that complies with ANSI B71.1 will carry an OPEI decal certifying compliance. This OPEI decal is your proof that the equipment you are considering complies with the latest industry standard and has been certified by an independent testing company.

Although riding lawn mowers and small tractors incorporate many safety features and conform to industry standards, they can still cause injury if misused. It is your responsibility as an operator to use your equipment safely.