Vision information > Vision and driving

When driving a motor vehicle a driver has to continuously monitor not only what is happening on the road but also the data on the panel board. The tilting of his head (in average around 30 degrees) leads to reduction of the sharpness of the image of events happening on the road which is caused by the movement of the eyes. When looking at the speedometer the movement of the eyes exceeds the target by 5 degrees in average and it is immediately balanced with the subsequent movement of the eyes. The creation of sharp image on the retina leads to its processing and to the realization of what is seen. However, we suppose that the size of the figures, which are being read, has to be at minimum 5 times bigger than the minimal size which enables them to be differentiated. Therefore the look can return to the original position only after the processing and implementation of the information.

Duration of this process is influenced by numerous factors such as age, physical condition, vigilance and experience. In average it is from 0.5 – 3s. At the speed of 100 km/h the vehicle travels from 14 – 86 m; at 160 km/h it travels 22 – 132 m. During this time the driver does not see anything and it is like the vehicle was controlled by a blind person.

Even a completely healthy person needs the time around 0.1 s for the visual input to be processed on the retina, registered and identified in the visual centers of the brain. During this time the vehicle will travel around 4.4 m at the speed of 160 km/h. Considering the blackouts of the stimulus from the periphery of the retina the distance can be increased to 7m. This means that the driver would register a rabbit coming from the side at the speed of 80 km/h not before the rabbit would be dead. Paradoxically it would be considered as the accident with an absent object.

A participant of the road traffic should be able to distinguish colors normally. The disorder of color vision is more common in men (8%) and less in women (0.4%). Around 80% of color-blind people have a minor disorder of perception of green and 25% have a more severe one. 10% of people have a minor disorder of perception of red and 15% suffer from more severe disorder. According to the new research around 1.5 – 2% of participants of the traffic suffer from disorder of the perception of red. We have to remember that the exceptionally dirty brake lights and sidelights will be recognized by them later or not at all. At the moment the treatment of this genetically conditioned disorder is not possible.

The easy legibility of the data on the panel board also contributes to the safety of road traffic. Different automakers use various colors for the panel board. The automaker SAAB prefers green, Ferrari substituted white for red-orange and then for green and Porsche uses yellow diodes with the wavelength of 588 nm. The concern Fiat prefers green and orange color. Ford considers calming green to be the best choice whereas Opel prefers neutral white. Renault did not choose any color as the typical one for the company. Daimler-Chrysler uses yellow but it also uses blue for the number of clocked kilometers and the outside temperature. BMW and Rover have been using orange since 1987 because they misbelieved that the right combination of red and green compensates both of the most common disorders of the color vision. Audi has white fittings with gray or bluish figures and VW has blue diodes with the wavelength of 465 nm and richness of 80-85%.

All companies argue that they are doing their best for the customers' benefit. In general it holds true that:

1. Disorder of the ability to distinguish red is accompanied by distinctly shortened spectrum on the long wave end.
2. The maximum of the brightness is moved from 555 nm to 520 nm. Yellow and green colors are perceived better in case of this disorder. Red fittings do not interfere with the adaptation to darkness but they worsen the close-range vision for people with presbyopia.
3. Green fittings are suitable for people with presbyopia. They allow them sufficient vision to the close range and also to the distance when using eyeglasses.
4. Blue is the least suitable for older drivers. Their ageing intraocular lens loses the elasticity and becomes yellowy or brownish. Incident light is then strongly absorbed and dispersed. Blue light causes also a mild myopia.
5. White light can dazzle. Bright signs on dark base improve the contrast. The ability to distinguish colour signs can be negatively affected by disorder of the eye ( cataracts, retinopathy) or by taking some medications.

The US navy can be the illustrative example of the change in opinions on the importance of colored indicators. Red color, which was used in submarines during the World War II, was the major cause of common headaches, blurred vision and difficulties in reading which were all caused by relative myopia. The subsequent change to blue color did not lead to expected positive effect on the adaptation and that is why they switched to neutral white that makes the adaptation easier when controlling devices.

It follows from the information listed above that the automakers should devote much more attention to the development of illuminated panel boards. Not only the drivers would benefit but it would also contribute to the road traffic safety.