Commercial-size riding mowers, including the popular zero-turning-radius mowers (Figure 1), are covered by a safety standard promulgated by the American National Standards Institute (ANSI).
 
Even though many of these mowers are used by homeowners, those that are designed primarily for commercial use are considered commercial machines. Thus, they fall under a commercial mower standard.

ANSI/OPEI B71.4-2004 Commercial Turf Care Equipment - Safety Specifications
This standard was developed by the Outdoor Power Equipment Institute (OPEI), an organization composed of manufacturers of this type of equipment, with assistance and input from more than 20 other technical organizations including the American Society of Agricultural Engineers. It was then reviewed and approved by ANSI. This is an industry consensus standard, meaning that manufacturers voluntarily comply with it; it is not enforced by any government agency.

Riding mowers that comply with this standard may have a decal on the machine certifying compliance (Figure 2). Compliance certification is often done by an independent testing organization, not the manufacturer. The manufacturer has to pay for the compliance testing. Not all manufacturers of commercial mowers choose to comply with this standard or obtain certification; only fully compliant mowers should be considered for purchase.

Guarding and Shielding
The standard lists specific areas that require guarding, such as rotating components, hot surfaces, pinch points, etc. and includes requirements for functionality and durability of the guards.

Labels and Instructions
The standard contains detailed requirements for safety signs and operator’s manual content. Durability of labels and safety signs is prescribed.

Operator’s Zone and Controls
The standard requires that the operator’s zone be protected from engine exhaust, moving components and battery, fuel, oil and coolant system components or reservoirs. A finger-probe test is required to ensure that an operator cannot reach into a dangerous area from the operator’s position. Operator-presence controls are required. This control must automatically stop the mower when the operator leaves the operator’s position. This is usually accomplished with a switch under the seat that disengages the mower clutch and engages a blade brake (or kills the engine) if the operator rises from the seat.

Stability and Overturn Protection
The standard requires testing of the mower on a tilt table to determine its susceptibility to side and rearward overturns. The mower must not start to tilt with a longitudinal slope of 30 degrees nor a lateral slope of 20 degrees. There are also requirements on braking on slopes. A rollover protective structure (ROPS) is recommended if the mower weighs more than 1,436 pounds and the tip angle is less than 40 degrees (many manufacturers now offer ROPS as standard on all zero-turning-radius mowers). This standard certainly does not prohibit the use of ROPS on smaller mowers, and some manufacturers do have ROPS as a standard feature on mid-sized as well as larger zero-turning-radius mowers. ROPS should be used on all zero-turning-radius mowers.

Mower Deck Safety Requirements
The standard has several requirements for mower deck safety including blade guarding, protection from thrown objects and blade impact resistance (when striking a solid object). A foot probe must be used to verify efficacy of the guarding. Blade tip speed is limited by the standard to 19,000 feet/minute (216 mph).

Other Features of the Standard
The standard also covers many other safety areas involving fuel, hydraulics, control layout, etc.

This standard, like most industry consensus standards, is constantly evolving. Industry committees work to update and improve the standard as new technology is developed. This effort includes making the standard relevant to new equipment designs and also requires that manufacturers constantly improve the safety features of their machines to meet new versions of the standard.

Although no standard can completely anticipate all hazards or prevent all accidents, this industry consensus standard goes a long way toward improving the safety of mower operators. Be certain that any mower considered for purchase is certified to be in compliance with the current version of ANSI/OPEI B71.4.