ESTIMATING COMPLIANCE WITH
THE 15-SECOND RULE FOR
DRIVER-INTERFACE USABILITY AND SAFETY

Paul Green

September 1999

This paper describes SAE J2365 (Recommended Practice for Calculating the Time to Complete In-Vehicle Navigation and Route Guidance Tasks), a draft procedure to estimate if the requirements of SAE J2364 (Navigation Function Access) are met. Application of these practices will enhance the safety, ease of use, and customer convenience of driver interfaces. SAE J2364 specifies that drivers should not be allowed to perform navigation-system tasks in a moving vehicle that take more than 15 seconds to complete when measured staticly. Tasks are defined to start when the driver's hands begin to move from the steering wheel and end when feedback from the final-switch actuation is processed.

The 11-step calculation procedure of J2365 involves determining exactly how each task (e.g., destination entry) is carried out, developing a pseudo-code description of the goals and methods used, determining the associated elemental tasks, and adding up the task times. Elemental times [reaching for a device, keying (cursor, letter, space, enter), mental activity, searching, etc.] were derived from the Keystroke-Level Model (Card, Moran, and Newell, 1983) in the human-computer interaction literature, specific automotive studies of navigation data entry (Manes, Green, and Hunter, 1998), and MTM-1 (Barnes, 1968).

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