London Ambulance Service Failure

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The London Ambulance fiasco


The London Ambulance Service (LAS) Computer Aided Despatch (CAD) system failed dramatically on October 26th 1992 shortly after it was introduced: • • • The system could not cope with the load placed on it by normal use; The response to emergency calls was several hours; Ambulance communications failed and ambulances were lost from the system.



A series of errors were made in the procurement, design, implementation, and introduction of the system.

©Ian Sommerville 2004

Software Engineering Case Studies

Slide 1

London Ambulance Service




Managed by South West Thames Regional Health Authority. Largest ambulance service in the world (LAS inquiry report) • • • • Covers geographical area of over 600 square miles Resident population of 6.8 million people (greater during daytime, especially central London); Carries over 5,000 patients every day; 2,000-2,500 calls received daily, of which 1,3001,600 are emergency calls.

©Ian Sommerville 2004

Software Engineering Case Studies

Slide 2

Computer-aided despatch systems


Provide one or more of the following:
• • • • Call taking; Resource identification; Resource mobilisation; Ambulance resource management. CAD software & hardware; Gazetteer and mapping software; Communications interface (RIFS). Radio system; Mobile data terminals (MDTs); Automatic vehicle location system (AVLS).



Consist of:
• • • • • •

©Ian Sommerville 2004

Software Engineering Case Studies

Slide 3

The manual system to be replaced


Call taking
• Recorded on form; location identified in map book; forms sent to central collection point on conveyor belt; Form collected; passed onto resource allocator depending on region; duplicates identified. Resource allocator decides on which resource to be mobilised; recorded on form and passed to dispatcher; Dispatcher telephones relevant ambulance station, or passes mobilisation instructions to radio operator if ambulance already on road;



Resource identification




Resource mobilisation




Whole process meant to take < 3 minutes.
Software Engineering Case Studies Slide 4

©Ian Sommerville 2004

Concept/design of the CAD system


Existing systems dismissed as inadequate and impossible to modify to meet LAS’s needs • Intended functionality “greater than available from any existing system”. To consist of Computer Aided Dispatch; Computer map display; Automatic Vehicle Location System (AVLS); Must integrate with existing MDTs and RIFS (Radio Interface System). Near 100% accuracy and reliability of technology; Absolute cooperation from all parties including CAC staff and ambulance crews.



Desired system:
• •



Success dependent upon:
• •

©Ian Sommerville 2004

Software Engineering Case Studies

Slide 5

Problems: Procurement (i)


Contract had to be put out to open tender
• • Regulations emphasis is on best price; 35 companies expressed interest in providing all or part of the system • Most raised concerns over the proposed timetable of less than 1 year until full implementation.



Previous Arthur Andersen report largely ignored
• • Recommended budget of £1.5M and 19 month timetable for packaged solution. Both estimates to be significantly increased if packaged solution not available; Report never shown to new Director of Support Services.



Only 1 out of 17 proposals met all of the project team’s requirements, including budget of £1.5M. Software Engineering Case Studies Slide 6

©Ian Sommerville 2004

Problems: Procurement (ii)


Successful consortium
• • • Apricot, Systems Options (SO), Datatrak; bid at £937k was £700k cheaper than the nearest bid; SO’s quote for the CAD development was only £35k • Their previous development experience for the emergency services was only for administrative systems.

Ambiguity over lead contractor. Systems manager: Career ambulance man, not an IT professional,...
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