In Pursuit of Improved Operator Performance

May 1, 2008
From Fighter Planes to Nuclear Power

The study of human factors engineering began in the World War II era, said David Stobhar of Beville Engineering, at the beginning of his presentation on enhancing operator performance this week at ABB Automation World in Houston.

“Current areas of study by the Center for Operator Performance include color usage in graphics and the effectiveness of simulators.” Beville Engineering’s David Strobhar related the process industry’s ongoing efforts to improve the effectiveness of operators.

“Military pilots were crashing fighter planes at an alarming rate in non-combat situations,” Strobhar explained. “Research revealed that well-trained pilots flying reliable planes were often confused by poorly designed control panels, especially in emergency situations.”

Further studies showed that pilots were overwhelmed with the amount of data presented, a situation similar to the alarm floods experienced today by many process plant operators. “Studies showed that pilots should focus on six particular parameters in trouble situations. Cockpits were redesigned and pilots were retrained based on these findings, and accidents decreased markedly,” he added.

Today, the Center for Operator Performance ( is an industry-academia collaboration formed to improve operator performance in process plants. The center was created to perform studies and provide process-industry-specific data to its members.

Membership is open to all individuals and organizations and currently includes major process end-user firms such as Nova Chemicals and process automation suppliers, including ABB. Wright State University in Dayton, Ohio, is the host university, and Louisiana State University in Baton Rouge, La., is also a member. The center performs small pilot projects to gather data and promotes the open flow of this information among members.

From Fighter Planes to Nuclear Power

After World War II, one of the next areas for human factors study was nuclear power plants. It was found that hard-wired alarms in nuclear plants were increasing at a rapid rate, from 300 alarms in 1968 to 1,200 alarms in 1978. This was another harbinger of alarm flooding, and the advent of digital control systems with CRT monitors increased alarms yet again to the point where operators were being assaulted with scores of alarms each minute during a process upset. Studies showed that a typical operator could only address 1-15 alarms per minute, the exact number depending on a variety of human factors.

Human factors that shape alarm response and other operator performance issues include interface/information system design, job design and automation/process demands. Other key factors include workspace/ergonomics, operator selection and training, and organization and staffing.

“Because there are so many factors affecting operator performance, problem study and analysis is very complex,” said Strobhar. “Each factor must be therefore be broken down and studied in detail to ascertain how changes can affect performance.”

In the area of workspace/ergonomics, it was found that colors and alphanumeric symbols are processed differently by the human brain. Colors are recognized very quickly by the subconscious, so a correctly designed color coding system can give operators nearly instantaneous recognition of trouble conditions. On the other hand, alphanumeric symbols are processed by the conscious brain at a much slower rate. The conclusion is that operator graphics should rely on colors to alert operators to conditions that need immediate attention.

Other studies have shown that operators often perform better when presented with abstract rather than realistic symbols. Military research again led the way by showing that pilots performed better when viewing graphic displays that represented an F-16 jet by a triangle with a 16 inside compared to a realistic depiction of the jet. The implication for process plants is that abstract representations of pumps, vessels and other components may work better than detailed drawings.

Other studies have shown that operators work better when information is presented to them in logical groups. Simply drawing lines around related alphanumeric information was found to greatly improve operator performance.

Research just completed by the center drew on military experiences in the area of decision-making. It was found that putting operators through simple and specific problem scenarios could greatly increase both the speed and the accuracy of critical decisions.

“Current areas of study by the Center for Operator Performance include color usage in graphics and the effectiveness of simulators,” concluded Strobhar. “Pending studies will look at alarm rates, knowledge management and virtual tools like 3D headsets.”