Accident prevention
Making streets safer for drivers and pedestrians
Improved visibility makes a major contribution to road safety. White light helps drivers to detect movement at the roadside faster and from a greater distance. It also gives them precious extra time to stop should a child, cyclist, pedestrian or animal unexpectedly cross their path, preventing serious injury or even fatalities.
Protecting pedestrians
The converse is also true; pedestrians are more likely to see oncoming traffic and react accordingly. There is even emerging research which proves that better visibility also lowers accident rates among pedestrians, because they are less likely to trip over obstacles or uneven surfaces on footpaths and pavements.
Driving down response times
 Research carried out at the Lighting Research Center in Troy, New York examined whether white light improves the (peripheral) vision of motorists. A special board was placed beside a stretch of road which simulated movement towards and away from the road. 13 subjects underwent a series of tests during daytime and then at night-time with CosmoWhite and yellow high-pressure sodium illumination.
The results are clear
 A total of 686 separate trials were carried out with the board moving in random patterns. Moved away from the road the correct response was to accelerate, moved towards it the driver was expected to brake. The results showed a statistically significant difference in response times between white and yellow light for braking and accelerating. In both cases, the response time with white light was lower.
The science behind the story
In order to see an object, there has to be a certain luminance difference (i.e. contrast) between the object and its background. The contrast detection threshold is the minimum difference required so you can make out the object (without necessarily being able to perceive the colour or detail). A lower contrast threshold means that it is easier to detect an object. Test show that white light gives a lower luminance threshold than yellow light, especially at large off-axis angles and low luminance levels. This means that it is easier to see people or other objects with white light, which contributes to improved safety for the driver as well as for other road users.
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