Room to manoeuvre

The design of CCTV workstations and the layout of the Control Room itself should all contribute to achieving the performance objectives set for your surveillance nerve centre. A so-called 'top down' approach provides a framework whereby vital decisions on such matters as equipment selection, operating practices, working environments and furniture selection are based on operational demands.

In practice, the limitations of CCTV operators are automatically included, and the potential mismatches between operator capabilities and system demands minimised by virtue of the aforementioned 'top down' approach.

When it comes to design, the start point is to spell out the goals of the Control Room, determine what systems are required to fulfil those goals and then begin what's known as an 'allocation of function'. This is basically a process involving the listing of those functions best performed by machines – such as speedy, repetitive calculations – and those for which a human touch would be somewhat superior.

The flow chart detailed in figure 1 presents the idealised path for the schematic introduction of ergonomics. In practical applications, many of the decisions have already been taken. It's worth bearing in mind that, however well designed a workstation might be, the overall system will fail if your CCTV operators are overloaded and required to undertake tasks for which they are poorly trained, or need to strain their eyes when attempting to read illegible monitor displays.

Basic principles of design
An ergonomic workstation design will ensure that equipment which is frequently used falls easily to hand and that displays – which need to be seen at all times – are both easily and clearly visible from the normal working positions. Arriving at a logistical layout can be achieved by following well-documented conventions in which controls are grouped by functions, the physical array of equipment takes account of comfortable reach zones and displays are located in such a way that they will maximise views for CCTV operators.

The workstation height should be designed so that the smallest operator can see over the top of any workstation-mounted equipment to either remote displays or mimic panels (figure 2). Meantime, the clearances underneath each worktop should allow for the tallest operator to sit comfortably. Bear in mind that the requirement for using non-electronic equipment must also be considered at this stage.

Layouts ought to have a built-in allowance for items such as log books, maps, clipboards and even coffee cups. An element of flexibility should be allowed for the positioning of such items as telephones, keyboards and writing areas. In this way, you'll enable your operators to change posture during their shift, thereby minimising the possible effects of fatigue.

On a practical note, when selecting workstation finishes it's best to choose low reflectance materials that are non-slip. Saturated colours should be avoided at all costs, while medium tone greys are strongly recommended.

When looking at the arrangement of monitors themselves, start your thought process by reviewing management objectives rather than attempting to discover how many monitors you might be able to pack around a given operator! This 'top down' approach recognises that the amount of information which can be handled by any one individual is limited. Therefore, there is a definite ceiling to the number of images that can be presented.

The maximum number of CCTV pictures which an individual operator can cope with really depends upon a combination of factors, including operator performance targets, the amount of activity associated with each picture and the level of detail which needs to be picked out. Even a single screen, with observations taking place every ten minutes or so, will mean that the detection of significant events is never hitting the 100% mark. Far less than that, in fact.

As a general Rule of Thumb, the maximum number of camera views that a single operator can use is likely to be 16 or less. Experimental evidence shows that, as the number of monitors increases, so the performance of observers undertaking detection tasks in town centres decreases. Even if the Control Room only has four monitors presenting views with a great deal of movement, detection rates will only be in the region of 83%.

In order to determine the most effective method of presentation, performance targets should be combined with picture information analysis and that information subsequently distilled into a number of monitors. Autocycling should always be avoided, as the soporific effects may seriously undermine operators' abilities to maintain a satisfactory degree of attention.

Monitors that are used for close inspection of CCTV images are commonly called 'incident' or 'spot' monitors, and positioned directly on the workstation(s). They should be sited directly in front of the operator at a distance of between 0.5 and 1.5 metres, and range in screen size from 9-16 inches across the diagional (figure 3).

Monitors may be mounted off the workstation, and are eminently useful in providing a general overview. Remember also that such monitors may well be placed at a greater distance away than those on the workstation, and can be of a larger size (this time around being – typically – 17-28 inches across the diagonal).

Design layout: the essentials
An ergonomic workstation layout will be based around a well-defined sequence of tasks, which broadly pan out as follows:

• determine the main tasks to be undertaken at the workstation;
  
• is the workstation to be used as an isolated unit, or in conjunction with overview displays (or indeed other workstations)?;
  
• establish the equipment to be used at the workstation, including priorities, frequency of use and the usual sequences of equipment operation;
  
• determine what sort of non-electronic job aids might be deployed (such as clipboards, log books and maps);
  
• for each type of equipment, consider the demands placed upon the operator in respect of displays and controls (for example, some displays might well be difficult to see at extreme angles, while certain controls – such as the keyboard – may need to be directly in front of the operator for touch-typing purposes, etc);
  
• develop a workstation layout based around acceptable reach zones and visual limitations;
  
• test out layouts with the operators themselves, including within that test period some typical simulations of task sequences;
  
• modify your ergonomic Control Room layout in the light of feedback from these trials;
  
• in finalising the workstation dimensions, consider the full range of users and the range of physical sizes they might exhibit (figures 4 and 5) – taking in very short women and larger men;
  
• take full account of all maintenance requirements and the removal of equipment from both work surfaces, such as larger visual display units and processors that may be stored within the workstation;
  
• look to provide those all-important footrests for operators where appropriate.

Good workstation design = improved operator performance
Environmental design can make a direct and tangible contribution to your CCTV operators' performance levels. For example, where speech communications are important for PA announcements, or the existing use of radio systems occurs, the auditory environment has to be appropriately specified. Ambient noise levels should be controlled by considering such factors as surface finishes, the noise output of all equipment in the Control Room and the control of external sources of noise.

Equally, air conditioning systems can be automatically set to increase the ambient temperature levels inside the Control Room in order to compensate for those times when that of the human body is naturally decreasing in the early hours of the morning. One of the most common criticisms of Control Room spaces is that they're either too hot or too cold, so make an effort to 'get it right'. Indeed, air quality and temperature can play an important part in keeping your operators awake in what is a sedentary yet taxing task.

Staying with the building services theme, lighting within your Control Room must be sufficient and suitable for all visual tasks. Where extensive arrays of CCTV monitors are used, together with visual display terminals, the potential for disabling on-screen/monitor reflections is high.

A lighting scheme largely based on indirect lighting, whereby the ceiling is used to reflect light down into the space, usually offers an effective solution (figure 6, left).

In designing the lighting scheme, attention must be devoted to the range of tasks undertaken (as well as the ages of the operators). Low lighting levels may be suitable for CCTV image monitoring, but will pose problems for paper-based tasks.

The type of space to be avoided
Some of the main considerations in Control Room layout are shown in figure 7 (below, left). Selecting the right shape and size of Control Room can go a long way towards ensuring that a workable space layout is achieved. If possible, rooms which are square should always be preferred. Conversely, spaces that are rich in pillars and/or strongly angled walls must be avoided at all costs.

As a rule, CCTV operators hate working in a windowless environment. Unless required for operational purposes, it's strongly recommended that a window or two is included as part of the Control Room design (primarily for psychological reasons). However, any such glazed areas will need to take account of security and the fact that, if positioned incorrectly, they may act as unwanted sources of both reflections and screen glare.