Human Oriented Procedure Design

Robert Mauro

Standardized operating procedures provide one of the most effective safeguards against errors in any technical profession.  Through standard operating procedures, safe practices can be taught and enforced.  However, to be maximally effective, these procedures must be designed to take into account the larger operational context.

Modern airline operations are highly standardized.  Standard operating procedures guide the pilots’ work from gate to gate.  However, these procedures are frequently sub-optimal.   Many procedures were originally developed from aircraft flight manuals modified to fit operational requirements.  Rarely was much thought given to the cognitive limitations of the humans operating the systems.  Over time, as aircraft and operations change, operating procedures must change as well, but frequently they change organically, growing new appendages to take into account the peculiarities of a new aircraft or operation.

Typically, changes in existing procedures are made gradually.  Individual procedures are modified to accommodate changes in the environment and equipment.  When the environmental and equipment changes are small, this process usually produces efficient adaptations.  However, over time this evolutionary process can produce unwieldy and even dangerous outcomes as old procedures continue to be revised and modified to accommodate more and more changes.  Periodically, the entire system of procedures must be evaluated to determine whether the accumulated modifications of individual procedures have generated problems.  If so, the system as a whole must be revised to produce an optimal set of standardized operating procedures.


To generate a set of maximally effective operating procedures, the current needs of the system as a whole – including the human operators and the operational environment must be considered.  We have developed a system for incorporating in the procedure redesign process, a process for ensuring that the engineering requirements of the aircraft flown, the operational needs of the airline and airspace system, and the psychology of the human operators are considered.  This system was developed and tested in conjunction with a major US airline.  This project had three phases.  During the initial phase, a team of pilots produced a detailed description of the airline’s normal operations and identified points at which there were known problems.  Researchers trained in cognitive science then assisted the pilots in identifying the situations and psychological mechanisms that may have produced these problems.  Based on basic psychological principles, new procedures were then designed to avoid these problems without creating new ones.


In some cases, the differences between the old and new procedures were quite dramatic.  For example, many procedures normally performed during approach and landing (a high workload phase of a flight) were moved to cruise (a relatively low workload phase of flight) or eliminated, thus allowing the pilots to focus their attention on critical items at a critical time.  To evaluate the new procedures, the Federal Aviation Administration approved a test run.  First pilots flying their normal routes were observed by a group of pilots trained as observers.  Then, some of the previously observed pilots were trained in the new procedures and observed as they flew actual passenger-carrying operations using these procedures.  The observers sat on the “jump seat” behind the crews and recorded the crewmembers’ behaviors on a detailed log.  An immediate drop in errors was observed.  The procedures were then adopted by the airline and the effect of the new procedures was examined 4 months and 8 months later (see Figure 1).  Analyses revealed a decrease of approximately 80% in procedural errors.  Similar results were observed for routine items and items identified as critical for safe flight.