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Devon Partnership Trust, who run mental health services across most of Devon, planned to implement a “choose and book” telephone booking system for mental health assessment. This would book patients into available diary slots for the appropriate local team. As this system was new, the trust requested help in forecasting the number of appointment slots to schedule into the diary to provide good waiting times for patients but without allocating excessive spare capacity to the system.
PenCHORD were asked to advise on how many appointment slots were needed in each team to meet waiting time targets. Simulation was used to assess the choose and book system and to demonstrate the principle of queue sharing, where waiting times may be reduced by allowing teams to share work when appropriate. Using simulation to examine the sharing of work between teams also allowed the system to avoid breaching waiting time targets. As a result of this work, the trust has significantly reduced waiting times for mental health assessment in Devon.
A simulation model was developed. Patients arrive at random and in proportion to the demand in each team region. The simulation model contains a virtual diary of appointment slots available for each team, with patients allocated to these diary slots. Patients can be seen by any team as identified in a “pooling matrix”. This was used to limit patients being seen only by their local team or by being seen by close neighbouring teams. In addition, a hypothetical model was tested where any patient may be seen by any team in order to understand the maximum beneficial effect of queue sharing.
Scenarios were tested with varying capacity within each team and also with varying strategies of sharing of work. The example below shows one example of queue-sharing between teams and demonstrates how most of the potential benefits of queue sharing can be obtained with local sharing between neighbouring teams.
The choose and book system has been implemented with local queue sharing. Appointment slots within the target time and within the local area are available for booking by patients. There was a significant reduction in waiting times achieved during the roll-out of the first area (with sharing between two teams as necessary), and once rolled out across Devon, the system resulted in a halving of the time patients had to wait for an initial assessment.
Devon Partnership Trust