Preventing Overturns with Riding Mowers and Lawn/Garden Tractors

Figure 1. Lawn tractor. When operating on a slope, the rear wheels should be on the uphill side.

You might think that riding mowers and lawn/garden tractors are small and low to the ground so overturns are not a problem. Unfortunately, this is not the case.

Riding mowers and small tractors can overturn to the side or rear fairly easily. Manufacturers have minimized overturn problems, and ANSI Standard B71.1, which deals with safety for these consumer machines, has extensive coverage of overturn safety and testing. Nevertheless, the operator has primary responsibility for preventing overturns. There are several things you can do to minimize the hazard.

Operate up and down slopes, not sideways!
It is safer to operate up and down a hill than sideways because normally the fore-and-aft wheel spacing is greater than the side-to-side wheel spacing. In other words, a tractor will roll over to the side more easily than it will roll over forward or backward.

Point your tractor downhill!
If you must operate on a slope, it is safest to point your riding mower or tractor downhill. Pointing the front of the tractor downhill puts the drive tires on the uphill side of the tractor. If you point the tractor uphill, the drive tires will be on the downhill side, and the torque reaction on the drive tires will tend to lift the front and cause the machine to roll over. As the front starts to lift, traction on the rear increases and the rollover tendency increases. By aiming the tractor downhill, if the uphill wheels (the rear wheels of the tractor) start to leave the ground, they will immediately lose traction and the rollover will stop. Mowing while backing up is normally not recommended, but, in the case of mowing slopes, it is safer to back up the hill and drive back down rather than driving up and down or driving sideways on the slope.

If a problem occurs, steer downhill - fast!
In some situations, it just isn’t possible to mow up and down a slope, and you must mow across a slope. If you are doing so and feel any instability, always steer the tractor downhill to stabilize it. Never turn uphill when the tractor feels unsteady. That will almost guarantee a rollover!

Watch out for holes or bumps!
When operating on a slope, dropping a wheel into a hole or lifting a wheel by driving over a bump can be enough to trigger a rollover. Be especially careful of rough ground on slopes.

Keep your speed down on slopes!
If you are moving slowly and your tractor starts to feel unstable, you may be able to correct the situation. If you are moving fast, the tractor may roll before you can do anything.

If you have to load your tractor on a trailer or truck, back it on!
The same principle of keeping the front pointed downhill applies when going up a ramp onto a truck or trailer. One of the biggest hazards comes not when going up the ramp, but when starting back down. If the operator is doing it wrong and backing down and hits the brakes, the torque reaction of the tractor can easily cause an overturn. Keep the front pointed down while loading and unloading.

Drive smoothly!
Many overturns are the result of fast turns or sudden stops. If you drive smoothly and minimize jerky operation, you will minimize the risk of overturns.

Don’t drive on slopes with loaded grass catchers!
Be sure your grass catcher is empty or nearly empty before mowing on a slope. A loaded grass catcher can have a big effect on the center of gravity of the tractor.

Don’t try to stabilize the tractor with your foot!
If the tractor feels like it might overturn, don’t put your foot on the ground to try to stabilize it. That is a good way to lose a foot to the mower blade. Just turn downhill.

Rollover Protective Structures (ROPS) are not required by the ANSI standard for consumer turf equipment, but the addition of ROPS would improve safety. A ROPS is especially important on zero-turn mowers.

12/1/2004 10:49:23 PM
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