Preprint: Final version of paper available from:
W O N G , W. & BLANDFORD, A. (2004) Information Handling in Dynamic Decision Making Environments. In D. J. Reed, G. Baxter & M. Blythe (Eds.), Proceedings of ECCE-12, Living and Working with Technology. York: European Association of Cognitive Ergonomics. 195-202.
Information Handling in Dynamic Decision Making Environments B.L. William Wong
Ann Blandford
Interaction Design Centre Middlesex University Trent Park Campus Bramley Road London N14 4YZ
[email protected]
UCL Interaction Centre University College London Remax House, 31-32 Alfred Place, London WC1E 7DP
[email protected]
ABSTRACT
In this paper we describe our observations about information handling in the complex and dynamic decision making environment of ambulance control, more formally known as Emergency Medical Dispatch. Our findings suggest that the information handling capacity of individual dispatchers and of the system as a whole is affected by the difficulties they face in handling information, and this is exhibited in an increase in the time taken to activate ambulances as workload levels increase. We identified 18 information handling difficulties from which we extracted 12 information design features that are expected to improve the information handling ability of the dispatchers in this study. KEYWORDS
information handling, dynamic decision making, emergency medical dispatch, ambulance control. INTRODUCTION
Information handling refers to the physical and cognitive activities performed by individuals to process, collate and extract information about processes or situations that they might need to make decisions about. Such activities include the grouping of related information so that they can be compared, or the updating of information about a situation. Information handling is particularly demanding in dynamic decision making environments, such as ambulance control, more formally referred to as emergency medical dispatch (EMD). In such domains, the operators of the systems that control the processes frequently have to make sense of often incomplete, uncertain, and voluminous amounts of information that arrive from different sources, such as different screens in the computer control system, different modalities such as verbal utterances and spatially meaningful placements of artefacts, and over a period of time
1
where information is received in incomplete units and out of sequence. The less able the supporting systems are in collating and integrating necessary information, the greater the likelihood that more time will be required by the operators to collate and integrate required information before they can make sense of it and then act on it, causing delays in what are often time-critical situations. Delays in response can aggravate a situation, or even loss of life. In EMD, for example, every delay of one minute can reduce the chances of survival for a person with Sudden Cardiac Arrest by 10% (National Center for Early Defibrillation, 2002) Such information handling difficulties represent a misfit between intention, and the means available to carry out those intentions. In information work, these indications are often difficult to overtly identify as they pertain to the goals (and hence information needs) of the decisions being made. Such difficulties also adversely impact the information handling capacity of the individual operators and of the system. In this paper we describe our observations about the information handling difficulties faced by dispatchers at one of the largest and busiest ambulance control centres in the world, and hypothesise about the relationship between the information handling capacity of the system, and the difficulties experienced. We suggest that the time taken to activate an ambulance may be used as a surrogate measure as an indicator of the information handling capacity of the EMD process. This paper is based on research into the nature of decision making and information representation in complex dynamic environments. Other aspects of this work have be reported elsewhere (Blandford, Wong, Connell, & Green, 2002; Blandford & Wong, 2004; Wong & Blandford, 2001a; Wong & Blandford, 2001b).
BACKGROUND
The ambulance control centre in which this study was based is among the largest in Europe. It receives more than 3500 emergency calls a day. It is staffed 24-hours a day, every day. The control room is divided into a call-taking area and a dispatching area. The call-taking area can be staffed by 22 call-takers. The control area is divided into seven sector desks that mirror the seven geographical areas of ambulance operations. Each sector desk is staffed by a team of three dispatchers. The most senior is the sector controller, or allocator. The allocator is assisted by a radio operator who communicates with ambulance crews who are attending an incident, and a telephone dispatcher who communicates primarily with ambulance crews that are still at their stations, and other agencies such as hospitals and other emergency service control rooms. All emergency calls are received by the call-takers who record the necessary details such as location of incident and nature of the emergency into a computer system. These critical pieces of information are electronically and immediately conveyed to the appropriate sector desk. In the meantime, the call-taker will ask the caller a structured set of questions, known as the Advanced Medical Priority Dispatch System (AMPDS), to prioritise the medical emergency. Over at the sector desk, the allocator reads the details that arrive on his or her computer screen, and then prints the details to a job card, allocates an ambulance, and instruct the radio operator or the telephone dispatcher to send the ambulance. The job cards are used to record events and changes in status of ambulances assigned to that job. The job cards are laid on the allocator’s desk to help them visually compare information or to act as reminders, and placed in a metal-slotted allocator’s box once the job is under way. At the time of this study, situation updates were hand-written on the job cards. METHODOLOGY
Observations and Contextual Inquiry. 4 allocators, 5 call-takers, 3 dispatchers, 4 radio operators and staff working on two specialist desks were initially observed and interviewed each for 60-90 minutes using the Contextual Inquiry approach (Beyer & Holtzblatt, 1999). Observing dispatchers at work allowed us to gain some familiarity with routine work and to study observable patterns of work. It also gave us an appreciation of the layout of facilities in the room and work areas, the positioning of information resources such as an electronic notice board that showed the number of calls waiting, and how information artefacts such as the job cards and the slotted metal allocator’s box, are handled, shared, and managed. The Contextual Inquiry approach was useful for asking probing questions about the reasons why things were done in particular ways. For example, when allocators placed two cards back to back, it indicated that the ambulance assigned to the first job, on completion, would proceed to the second. The physical placement of information artefacts held special meanings that were discovered largely because the study was based in the context of
2
work in the control room. However, due to the constant and heavy workload, discussions were frequently interrupted and hence not possible to probe deeply into any particular issues. Critical Decision Method interviews. In addition, 9 allocators and 4 radio operators were interviewed individually to investigate in detail the decision making strategies involved with 11 different major incidents. We used a retrospective protocol analysis interview method called the Critical Decision Method, or CDM, (Hoffman, Crandall, & Shadbolt, 1998; Klein, Calderwood, & Macgregor, 1989). During the one-toone, 60 minute long interviews, they were asked to recall a particularly memorable incident that they had personally experienced in the course of their duties. A time line of each incident was developed then used as a framework to probe the interviewees’ memories about what they did, what cues they attended to and considered, and the actions they took at each decision point. The data from the observations, Contextual Inquiry and CDM interviews, was analysed using a qualitative data analysis technique called Emergent Themes Analysis (Wong, 2004). Workload analysis. Response time data was acquired from the management information department and analysed with the statistical analysis software SPSS to profile the workload that dispatchers face. WORKLOAD CAPACITY
AND
INFORMATION
HANDLING
The analysis of the time taken to convey dispatch instructions to ambulances, i.e. activation time, was found to increase significantly once a particular workload threshold is crossed. The average activation time increased from 2 min 8 sec to 3 min 38 sec as workload increased from a low workload band of 2991 calls per hour, to a high workload band of 105-156 calls an hour. A t-test showed that the difference in activation times is significant between the two workload bands (p
