DIRECTION OF TRAVEL

nvestigating road lighting, Yang and Wei's pilot study examines whether an improvement in visual performance can be achieved by enhancing the chroma of target objects, using light sources with a larger gamut area. The experiment involved a calibrated computer display to provide a 1.5 cd/sqm uniform background with a fixation point at the centre of the display, while an off-axis target was displayed in a random direction at 13.5 degrees from that point. Twelve observers aged between 22 and 28 years with normal colour vision took part. The luminance, hue and chroma of the target was varied, and luminance values chosen to provide a negative (0.5 cd/sqm), neutral (1.5 cd/sqm) and positive (5.0 cd/sqm) contrast. Four hues were used, red, green, blue and yellow. The quantity of chroma levels varied subject to the hue and luminance due to the gamut of the display.

It was found that for both negative and positive luminance contrast the observers' detection rate was 100 per cent and reaction time was short. However, when the luminance contrast was zero, lower detection rates and longer reaction times were experienced, except for when the target had a higher chroma value. In these instances the detection rates and reaction times were similar to those with a negative or positive luminance contrast. The authors therefore note that enhancing colour contrast can be as effective as enhancing luminance contrast in improving visual efficiency.

Fotios and Robbins present a research note on illuminance on P-Class, or subsidiary, roads. The authors begin by presenting the evolution of British Standards in their approach to the specification of road lighting, dating as far back as 1927. The latest standard, BS 5489-1:2013 gives requirements for average and minimum illuminance for six classes of P-class roads.

The authors note that road lighting documents tend to state 'average illuminance' but do not clarify which type of average – I

Iain Carlile looks at three of the most recently published Lighting Research and Technology papers on the lighting of roads and train stations

while it normally refers to mean, it could also refer to median or mode. They note that mean has the disadvantage of the value being susceptible to outlying values (unusually small or large in comparison to the rest of the data set). They also note that median is less affected by outliers.

From an analysis of illuminance at 30 subsidiary road locations it was found that median would be a more appropriate measure as the illuminances in the array of measurements did not have a normal distribution. Typically the median illuminance was 16 per cent lower than the mean. While mean and median are strongly correlated, the authors found the median was a more appropriate measure of central tendency. They further recommend that design recommendations should state if the mean or median is required and not just the average.

Hughes et al investigate methods of using lighting to influence passengers’ movement and behaviour in UK train stations. This poses many challenges, with rail stations varying in size, operating hours, fluctuating peak/off-peak times, and varying types of spaces (indoor, outdoor, modern, heritage). These can all influence passenger movement and cause overcrowding on platforms, bunching at intersections, and blockages on stairways and bridges.

From a review of 36 research papers and three review papers on the subject of behaviour and lighting, the authors identified a number of ways of using light to subtly guide and influence passengers to move through the station and use platforms more efficiently. These included varying intensity, colour (both CCT and hue), flicker/flash rate, position/direction and source/operation. Working with stakeholders and lighting technologists, the findings of the literature review were used to identify applications of light to influence train passengers, including: • Zones of light to identify effective boarding positions • Zones of light to encourage passenger dispersion along the platform • Zones of light to indicate optimum routes • P ulsing/chasing lights to determine bi-directionality in crowd movements • P ulsing/chasing lights to indicate appropriate walking pace • C hanges in properties to affect subjective mood/feelings of wellbeing and safety The authors suggest these six applications be used to inform future research.

Iain Carlile FSLL is a past president of the SLL and a senior associate at dpa lighting consultants

Lighting Research and Technology: OnlineFirst

In advance of being published in the print version of Lighting Research and Technology (LR&T), all papers accepted for publishing are available online. SLL members can gain access to these papers via the SLL website

Road lighting: A pilot study investigating improvement of visual performance using light sources with a larger gamut area

B Yang and M Wei

Research Note: Describing average illuminance for P-class roads

S Fotios and C Robbins

Identifying new concepts for innovative lighting-based interventions to influence movement and behaviours in train stations

N Hughes, B Ryan, M Hallewell, N Coad, A Grant, N Parrott, S Roberts and K Thompson