What are the options for adaptive driving controls for people with disabilities
By Mark Smeiska, Assistive Technology Specialist   

There are many types of adaptive driving controls and many different operations to be controlled to operate a vehicle. The primary functions are steering and the brake and throttle. These are three things that the operator must have complete control of to safely drive. The top level of secondary driving functions is the operations that need to be accessed when the vehicle is in motion. These functions include directional signals, the horn, lights, dimmer and windshield wipers and washer. The next level of secondary functions are the things that the driver needs to control but that can be done when the vehicle is not in motion such as ignition/start, transmission, parking brake, door locks, windows and climate control. Other things the driver may want to be able to access are cruise control, the radio, a phone and more. 
This article will deal with different methods of operating the throttle and brake. This article is not intended to cover all methods of operating the throttle and brake, but is intended as a general overview of the most common options available. This article is also not intended to recommend any particular type of driving control for use. The only safe way to determine appropriate driving equipment is by having an evaluation completed by a certified driver evaluator.
There are many alternatives to operate the throttle and brake. One of the most basic adaptations is pedal extensions. Pedal extensions consist of adding some type of material to the existing throttle, brake or clutch pedal to extend it closer to the driver for better access. This modification is intended to help people who have a difficult time safely reaching the factory equipped pedals. Most commonly used for people under five feet tall, pedal extensions have been as simple as clamping, screwing or taping blocks of wood to the pedals (taping a pedal extension on is never a good idea). On the other end of the spectrum, there are custom pedal extensions that are easily removed to make it simple and safe to switch between drivers with different needs. There are also pedal extensions that mount to the floor and can be folded out of the way when not in use. Good pedal extensions must be of an appropriate length for the driver and firmly attached to prevent unintended movement. They must also have a slip-resistant surface to prevent the operator’s foot from sliding off the pedal unintentionally. Pedal extensions should be removed when the vehicle is taken in for service to prevent use by untrained drivers.

Pedal extension
Pedal extensions allow people
who cannot otherwise reach the
throttle and brake to drive.

Left-foot accelerators are a device that transfers the operation of the throttle from the right side of the brake pedal to the left. These are intended for use by people who have had a stroke affecting the right side and people with right leg mobility issues or amputations. Most modern left-foot accelerators are removable or can be deactivated when other people drive the vehicle. Some vendors do not install left-foot accelerators because of the difficulty in obtaining liability coverage for the vendor. 

Left Foot
A left-foot accelerator may be a
good solution for a person who
can't use their right foot but can
use their left. 

Hand-operated driving controls come in many different varieties. Mechanical hand controls have a direct mechanical connection between the operator’s hand and the throttle and/or brake pedal. Servo-operated driving controls are operated via an input device that controls the movement of servomotors that are attached to the throttle and brake pedals. Most hand controls are used to operate both the throttle and brake, but some are used to operate only one function. Single-function hand controls are rarely used, but can be a perfect solution to fill the needs of some drivers. 

Hand controls
There are many types of adaptive
hand controls for driving, including
the push/rock type pictured here.

Mechanical hand controls are the most common and most reasonably priced option available. With most mechanical hand controls the brake operation is done by pushing the input device toward the front of the car to activate the brake. The majority of hand controls are mounted below the steering column, with rods and/or cables attached to the throttle and brake pedals. For many years there were only three possible actions that were used to operate the throttle. There are now additional methods available. The most common method is a pull-down-type action in which the driver pushes a lever toward their lap to engage the throttle. Another early method to operate the throttle is a pulling motion in which the operator pulls the lever towards their chest. The last of the early throttle operation methods is a twisting motion of the lever to operate it. This twisting motion is very similar to that of a motorcycle throttle. A more recent adaptation of the twist-type throttle was created by adding a vertical lever. This is referred to as a rocking-type throttle. This later entry into the market has become a very popular type of hand control. 
Another more recent type of hand control to enter the market is a vertically-mounted lever attached to the floor between the driver and passenger. This type of driving control also pushes towards the dash to operate the brake. A pulling or twisting motion is used to operate the throttle. The advantage of this type of hand control is that it leaves the area below the steering column unobstructed, which can be a significant advantage for people who have long legs or need added space when transferring in and out of the driver seat. Some modern cars have very little space available below the steering column.   
Servo-operated hand controls have used three different types of servomotors. Servo-operated controls use an external power source to amplify the input from the operator, minimizing the amount of effort required to drive. Vacuum- and air-pressure-operated servomotors require a pump to create the vacuum or compressed air to apply the throttle or brake. This is controlled through an input device that typically consists of a small push/pull-type lever. The third type of servo-operated hand control uses electronic motors to operate the throttle and brake. This hand control has several sizes of lever depending on the user’s strength and range of motion. Although rarely seen in the United States there is another type of servo throttle input available. To activate the throttle on this style of hand control there is a ring a little smaller than the steering wheel that is placed on the steering wheel. This ring is pushed with the driver’s thumb to engage the throttle.
To prevent accident, injury or death, all of the equipment discussed above should never be operated by people untrained in its use. All driving controls should be inspected, lubricated and properly maintained for the safety of the driver and others. 
Future articles will cover many of the options available for controlling the vehicle steering and many of the secondary functions needed to operate a motor vehicle. 
For more information, call 414-291-7520 V/Relay.  

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