White light is the right light

Given the much-publicised rising crime figures in the UK ('Gun Law Britain?', SMT, November 2003, p3), it's hardly surprising that organisations in both the private and public sectors are paying more attention to – and investing further in – security and related safety measures. The noticeable rise in the installation of CCTV systems, the growing deployment of private security officers and a greater emphasis on security alarm systems are all in direct response to this escalation.

That said, the major contribution that high quality lighting can make – both as a security measure in its own right, and as a contributor to making other security systems that much more effective – is frequently overlooked when companies are considering new protection measures. This is partly due to the fact that many security and safety initiatives have tended to be purely tactical. That particular status quo is set to change with the advent of recent legislation and a raft of new initiatives.

Under Section 17 of the Crime and Disorder Act 1998, all local police authorities have a duty to consider crime and disorder reduction while exercising any of their duties. Some legal experts believe that this particular Act, allied to the Human Rights Act 1998, could lead to actions by citizens against local authorities and organisations if appropriate security and crime reduction measures aren't enforced.

There are a number of initiatives out there designed to help encourage the end user in planning crime prevention measures. One such scheme is 'Secured By Design', organised by the police and endorsed by the Association of Chief Police Officers (with the backing of the Home Office).

Security planning reflected by 'Secured By Design' principles makes a clear distinction between reducing the opportunity for crime and the fear of crime. Effective lighting can play a highly important role in both of these areas.

Assessing a lighting scheme
There are a number of guiding principles that might be used to assess a given lighting scheme. These are as follows:

• consider the total area to be lit, and how the lighting will integrate with adjoining developments;
  
• assess specific high risk areas such as walkways, steps, ramps and parking bays, etc;
  
• beware of crime 'hot spots', where the very nature of a building might influence crime and social behaviour traits;
  
• think about the needs of the likely users of the space;
  
• assess links and short cuts joining two or more popular places;
  
• appraise the availability of suitable locations for light fittings;
  
• look at the need for lighting controls/timers;
  
• consider the environmental factors at play (including energy efficiency and light pollution... whereby too much unwanted light is projected into the night sky).

Finally, think about the lamps (ie the light sources) to be used in the luminaires (light fittings) as your decision here can have a fundamental impact on the quality and colour of light emitted from the final design.

Remember that the human eye judges lighting subjectively. The latest research suggests that the old lumens per Watt method of judging lamp efficiency is incorrect, since it's not the amount of light produced that's important but how well the eye can see using that light (in particular when overall light levels are reduced).

In this situation, our eyes' sensitivity to yellow and red light greatly reduces, while the response to blue and green light increases. Sodium-based light produces most of its light output in the yellow spectrum. While in theory its light output is high, what's actually seen by the eye under such yellow lighting is comparatively low.

Alternatively, while its lumen output is slightly lower, the white light of metal halide lamps is spread more evenly over the whole visual spectrum, helping to improve the accuracy of identification and reducing anonymity. Looking straight ahead, the effective lumen output is 100% higher for metal halide lamps than for high pressure sodium sources. For peripheral vision, detection and reaction to visual stimuli is six times higher.

Colour identification is also improved under white light. The best light source is the sun, which is given a score of 100 using a measure known as the Colour Rendering Index (CRI). Other lamps are measured as a percentage against this benchmark. High pressure sodium lamps boast a CRI of only 20, while metal halide lighting will typically score around the 70 mark. Hence CCTV is far more effective when used in conjunction with the white light of metal halide or fluorescent lamps.

By taking a long, hard look at the lighting scheme your business provides, and considering whether or not it's effective from a security and safety point of view, it's possible to make a real and genuine difference to the potential risk and fear factor.