Interpretation ID: 2853o
Administrative Manager, Engineering
FWD Corporation
Clintonville, WI 54929-1590
Dear Mr. Steenbock,
This letter responds to your letter of last year asking whether it is permissible under Federal motor vehicle safety standard 124, Accelerator Control Systems (Standard 124), to install a locking hand throttle control in a new motor vehicle. I apologize for the delay in this response. The answer to your question is no.
While you do not describe what you mean by a "locking hand-throttle control" in your letter, I understood you to mean the following. Some vehicle design configurations have a hand-operated device on the steering column that connects to the throttle lever. In most design configurations, a driver may operate this device either by a turning or push-pull action. This device is commonly referred to as a "hand-throttle control."
These hand-throttle controls have two common applications. First, vehicles designed to be operated by physically disabled persons sometimes use a hand-throttle, rather than a foot-pedal, as the means for applying the actuating force that regulates the throttle valves and vehicle acceleration. Second, on some commercial vehicles, a hand-throttle control can be part of a system that allows a driver to use a hand control to regulate the engine fuel supply, and so to operate a power-driven accessory such as a generator while the vehicle is stationary with the transmission out of "drive." While the intended use of a hand-throttle control in a commercial vehicle may be only to power such an accessory, a driver still could use the throttle to control vehicle acceleration. Nothing in Standard 124 prohibits a manufacturer from installing a hand-throttle control in its vehicles.
Some hand-throttle controls have a mechanism that permits the driver to lock the throttle valves open in a position other than idle even after the driver removes the actuating force. When you asked about "locking hand-throttle controls," I understood you to be referring to this type of design.
These "locking hand throttle controls" are expressly prohibited by Standard 124. Paragraph S5.1 of that Standard requires that the throttle valves must be capable of returning to the idle position whenever the driver removes the actuating force. The purpose of Standard 124 is to minimize the risk of accident due to engine runaway. (37 FR 7097, April 8, 1972.) Consequently, a locking hand-throttle control would increase the risk of the very harm Standard 124 was adopted to address.
I hope you find this information helpful. If you have further questions, please feel free to contact Joan Tilghman of my staff at (202) 366-2992.
Sincerely,
Erika Z. Jones Chief Counsel
ref:124#571 d:3/17/88