This Safety Awareness Bulletin (SAB) is intended for Power System Operations (PSO) but is provided to all TVA
organizations for information.
A recent vehicular accident involving an employee hand injury during the airbag deployment, underlines the need to
provide updated information on recommendations for driver’s hand positioning on the steering wheel of a vehicle
equipped with Supplemental Airbag Restraint systems.
How Air Bags Work
To have a frontal (driver or passenger) air bag deploy, certain criteria must be met. One of these criteria is that the frontal
impact must be within a 60-degree window, occurring within 30 degrees from the vehicle's centerline. Another key
element is that the crash forces are equivalent to a head-on collision with an immovable barrier at 10-15 miles per hour.
Because a typical automobile accident only lasts about 0.125 (1/8th) of a second, air bags deploy within 15 to 20ms after
the initial crash impact. To create a protective cushion between the occupant and the vehicle's interior, the air bag inflates
at speeds up to 200 mph within approximately 30ms after impact. This allows the occupant to contact a fully inflated bag
within approximately 45 to 50ms after the initial crash impact. Approximately 100ms after impact the bag deflates.
The entire deployment and deflation cycle takes place in less than one second.
Updated Recommendations for Hand Placement on Airbag Equipped Steering Wheels
Steering: Proper Hand Position
Opinions vary as to exactly what constitutes proper hand position on the steering wheel. You probably grew up with the
10:00/2:00 position. This position is no longer acceptable because deploying airbags may throw the drivers hands into his
face. We recommend the 9:00/3:00 position. Now that driver side airbags are standard equipment in the steering wheels
of new cars, the 8:00/4:00 hand position has become an acceptable option. Either of these positions, or anywhere
between them, is a good hand position as long as you are comfortable. Try several hand positions while
parked. Point out the pros and cons of each and share your expectations with new drivers. Do not allow new drivers to
drive with only one hand on the steering wheel, wrists crossed, or both hands at the 12:00 position. Again, airbags are the
factor. Should the airbag deploy, you want to be sure the hands are directed out or down, not in the drivers face.
We recommend that drivers steer using the modified hand-to-hand method. We call it “modified” because you never
actually bring your right hand to contact your left hand. You were probably taught hand-over-hand and, prior to driver side
airbags, that was acceptable. In today's automobile it is important to keep your hands away from the top of the steering
wheel. If the airbag deploys, you will likely punch yourself in the face with the force of the airbag's deployment as well as
the force of your own forward motion in the vehicle.
When using modified hand-to-hand steering to turn, the left hand grasps the wheel between 7 and 8 o'clock and the right
hand grasp the wheel between 4 and 5 o'clock. Depending on the direction of the turn, the right or left hand pushes the
wheel up and the opposite hand slides up, grasps the wheel and pulls down to continue the turn. Never bring your hands
above the 11 and 1 position. While the pulling hand moves down, the hand that initially pushed up slides back toward its
original position to make adjustments as needed. Simply reverse the modified hand-to-hand process to bring the vehicle
onto your intended path. Initially, drivers may be confused about modified hand-to-hand steering. If they are shuffling the
steering wheel, encourage them to use the full range of motion. It may also help to have them focus on the smoothness of
the turn.
With the new driver's hands positioned at 7/9 and 3/5, a more natural seated position, there tends to be less muscle
stress, hence less weaving in a lane. With the arms next to the body, it is more natural to keep both hands on the wheel at
all times. Since the hands and arms never cross over the steering wheel there is less chance of injury to the face induced
by the hands or arms in the event of a frontal crash in a vehicle equipped with a driver side air bag.
Practice proper hand position and steering method using a Frisbee, paper plate, or other disk or wheel before new drivers
get behind the wheel of a car.
This bulletin was prepared by: Daryl Smith
Submitted by SL Breeden
