Types of ROPS (Roll-Over Protective Structure)

The most common ROPS is the two-post ROPS, with two upright posts (may be vertical or slightly tilted) mounted to the rear axle. Some vineyard or orchard tractors have a mid-mounted two-post ROPS, where the ROPS is mounted to a frame on each side of the tractor engine, ahead of the operator. There is the four-post ROPS, less common than two-post ROPS, with mounts both on the axles and on the frame ahead of the operator, or sometimes with all four posts mounted to the tops of specially-reinforced flat-top rear fenders. There is also the ROPS cab, where the cab structure is designed to act as the ROPS. As more tractors are sold with cabs provided by the tractor manufacturer, the ROPS cab makes up a greatly increasing proportion of all ROPS. Regardless of the type of ROPS, they all have specially designed mounting plates and mounting points for structural integrity.

Two-post ROPS are constructed in a variety of configurations. A common configuration uses a crossbar welded to the posts, making the ROPS a large one-piece structure. Another configuration uses a bolted crossbar, so that each post and the crossbar are separate pieces and can be installed piece by piece. A third type uses one piece of steel, either flat or tubing, which is formed into a ROPS by bending it into a U-shape. Another configuration, seen on some compact utility tractors, uses a plate mounted to the rear of the transmission housing, extending up behind the seat, to which is bolted a rectangular formed loop of steel that serves as the actual ROPS uprights and crossbar.

Foldable two-post ROPS are available for many tractors. These use a carefully-designed hinge on each post, or in the case of the small ROPS mounted to the rear of the transmission housing, a single hinge, with pins to hold the ROPS upright. Mid-mount ROPS on vineyard or orchard tractors fold down at the tractor frame. In all cases, the ROPS is designed to be folded down only when used in low-clearance areas, and kept upright up the rest of the time to provide rollover protection.

Seat Belts

When a tractor overturns, the ROPS is designed to do two things. First, in many situations, the ROPS will limit the overturn to roughly 90 degrees. In other words, when a tractor overturns to the side, the ROPS prevents the tractor from rolling farther than just landing on its side. If the tractor overturns to the rear, the ROPS will often limit the overturn to roughly 90 degrees, so the tractor stops with its nose pointed up into the air. Second, if the overturn has enough energy to cause the tractor to roll over onto its top, or in the case of a side overturn on a steep slope, even continue rolling past that point and make one or more complete rolls, the ROPS is designed not to crush, but to create a “zone of protection” that keeps the tractor from crushing the operator.

The seat belt is intended to keep the operator inside that zone of protection. The more violent the overturn, the more likely the rotating force will throw the operator outside the zone of protection. Many operators think they can jump clear, and while that has happened on occasion, overturns usually occur so quickly that a person cannot jump clear of the tractor. Seat belts also have the added benefit of protecting against falls from the tractor when going over rough ground, or if the tractor is struck by another vehicle on the road.

It is often assumed that the seat belt must be worn for the ROPS to be effective. For the ROPS to be effective in all situations, this is true. However, some tractor owners who have decided they will not wear the seat belt then decide not to retrofit a ROPS, because they think without the seat belt buckled, the ROPS will not provide any protection. This is a false assumption. A ROPS without the seat belt is better than no ROPS at all. Don’t decide against a retrofit ROPS just because you doubt you will wear the seat belt.

There are two reasons why a ROPS without seat belt is better than no ROPS at all. First, as mentioned previously, in a rear overturn, tractors with ROPS will usually rotate about 90 degrees and stop with the nose up in the air. The operator would most likely still be in the seat even without fastening the seat belt. Without a ROPS, the tractor will go all the way over and crush the operator. If a tractor with ROPS does roll all the way over in a rear overturn, the tractor will not land flat on top of you. Second, many side overturns are slow enough that the tractor only rotates about 90 degrees and ends up on its side. While it is still possible for the operator to fall from the zone of protection and land beneath the tractor or the ROPS, it is also quite possible to stay in the seat or operator’s station and not be injured, or suffer only minor injuries. Of course, wearing the seat belt is the safest thing to do.

ROPS Standards and Certification for Wheeled Agricultural Tractors

In the United States, the federal government does not regulate agricultural tractors and other farm equipment, unlike automobiles, which are regulated by the National Highway Traffic Safety Administration (NHTSA) of the U.S. Department of Transportation. The Occupational Safety and Health Administration (OSHA) does not regulate tractors and farm equipment, despite what some people believe. OSHA regulates employers; whether it is a punch press in a factory, a forklift, or a tractor, it is the employer who is responsible for meeting OSHA standards, not the equipment manufacturer.

OSHA does not certify ROPS. It is a common misperception that OSHA certifies ROPS. It is up to the ROPS manufacturer or supplier to certify that a ROPS meets a given standard. There are ROPS performance standards from OSHA, SAE (Society of Automotive Engineers), ASABE (American Society of Agricultural and Biological Engineers, formerly ASAE), CSA (Canadian Standards Association), ISO (International Organization for Standardization), and other international organizations, economic unions, and nations.

Regardless of the standard to which the ROPS is certified by the manufacturer or supplier, it should have a label specifying which standard was met.

Not all ROPS standards require seat belts. The OSHA, SAE, ASABE, and CSA standards require seat belts and seat belt mountings to be tested as part of the standard. The common standards used for ROPS certification in North America are OSHA 1928.52 or 1928.53; SAE J1194 or J2194; ASAE S383, which was withdrawn and replaced with SAE J1194; ASAE S478 (for compact utility tractors; also approved as an ANSI standard by the American National Standards Institute); and CSA B352.0 and 352.1. These standards require testing the seat belt mounting. They also require that on a suspended seat, which means the seat is on a suspension and moves up and down as the tractor goes over bumps, the seat belt must be mounted to the seat to move with the seat. In other words, when the operator buckles and tightens the seat belt, the belt keeps the same tightness as the seat moves up and down, and the seat and seat belt anchorage must be able to withstand the forces generated during an overturn.

However, the ISO standard for ROPS, ISO 5700, does not require seat belts. Thus a ROPS certified to ISO 5700 would not require a seat belt and would not require any seat belt supplied with the ROPS to be mounted to a suspended seat. Not having a seat belt attached to a suspended seat would not meet OSHA requirements.

Do Not Make Your Own ROPS or Have It Fabricated by a Shop

ROPS are carefully engineered structures designed to absorb some energy while maintaining structural integrity. Each ROPS is designed for a certain tractor weight range. ROPS use special steel to avoid cold weather brittleness and use hardened bolts to prevent failure at the fasteners. ROPS are designed with mounting plates that fit on the axle in such as way as to maintain axle housing integrity. All bolted or welded joints are designed and constructed with the necessary strength, and welds are of the highest quality in terms of penetration and size. ROPS are tested using a standardized procedure with very large forces, to assure the structure performs properly during an overturn. Even experienced machine shops or blacksmiths should not make a ROPS. ROPS are carefully engineered and tested so that every joint, every piece of steel, and every fastener, in conjunction with the appropriate tractor, withstands the necessary stresses and strains and performs properly, and does not deflect into the operator zone of protection as defined by ROPS standards. There is no guarantee that a homemade or shop-made ROPS will meet all these criteria.

FOPS (Falling Object Protective Structure)

In areas where falling objects pose hazards to a tractor operator, FOPS is specified to prevent those objects from striking and possibly killing the operator. Like ROPS, a FOPS is a carefully engineered structure that must meet certain performance standards. A FOPS is a canopy or cab roof that is specifically designed to meet certain standards by preventing penetration of a standard object falling from a standard height, and must protect a specified area. Typical fiberglass or steel canopies attached to ROPS, or typical cab roofs, are not FOPS unless they are certified by the manufacturer as meeting the appropriate FOPS performance standard. Of course, a FOPS gives the operator the advantages of sun and weather protection provided by an ordinary canopy. While FOPS are available for some two-post ROPS, they are more commonly found on four-post ROPS or ROPS cabs, particularly on tractors used for construction work.

When ROPS Became Standard Equipment on Tractors in the U.S.

As mentioned above, the federal government does not regulate agricultural tractors and machinery. The ROPS standards previously described are voluntary standards in the U.S., followed by manufacturers on a voluntary basis. Prior to 1985, the ASAE (American Society of Agricultural Engineers, now ASABE) standard for farm equipment safety, S318, said that ROPS “should” be provided. Thus since the late 1960’s and early 1970’s, tractor manufacturers have offered ROPS as optional equipment. Cabs built by the tractor manufacturers during this time were often ROPS cabs, and certainly by the mid-1970’s all manufacturer-supplied cabs were ROPS cabs. But ROPS was still an option.

Then, in 1985, the language in ASAE S318 was changed from ROPS “should” be provided to ROPS “shall” be provided, meaning that to comply with the standard, tractor manufacturers had to make ROPS standard equipment on all agricultural tractors. Again, this is a voluntary standard followed by the tractor manufacturers. Of course, prior to that time the OSHA standards required ROPS on agricultural tractors, but this only applied to farms that were subject to OSHA or equivalent state standards, and as explained earlier, applied to the farm operator, not the tractor manufacturer. A tractor made after 1985 that lacks ROPS would have had its ROPS removed by an owner.