The 15-Second Rule for Driver Information Systems

Paul Green

May 1999

The 15-Second Rule specifies the recommended maximum time for drivers to complete navigation-related tasks involving visual displays and manual controls in a moving vehicle. Compliance is determined by calculating task time assuming the vehicle is parked, a simplifying assumption. Task time is (1) correlated with crash risk, (2) much easier to measure than alternatives such as total eyes-off-the-road time, and (3) is computable early in development, thus supporting iterative design. This rule is the basis for a proposed Society of Automotive Engineers (SAE) standard (J2364) and a related international standard to promote the safety and usability of driver interfaces. A compliance standard (SAE J2365) and a related international standard for compliance are under development.

The 15-Second Rule (1) is consistent with existing national and trade association guidelines, (2) is consistent with accepted vehicle design practice and, (3) more generally, minimizes harm to drivers. Designers should realize that a good case can be made for lower task time limits (e.g., 10 seconds) to further reduce opportunities for interface-induced crashes, and achieving that limit is desired where feasible. A practical result of the 15-Second Rule is that most destination entry tasks will not be allowed in moving vehicles.

The process of developing this rule also provided useful insights into general practices for creating Intelligent Transportation System (ITS) standards. In particular, the use of consultants is recommended to accelerate standards development. Further, standards should be based on human factors guidelines and research as interpreted by human factors experts, not interested parties, and emerge from a process true to SAE Technical Standard Board rules.

Download ITSA-Green 1999 (.pdf)


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