researchers of the University of Granada (UGR) They have designed a new method, much safer and cheaper than the one currently used, to calculate the lighting needs of a road tunnel. His work is especially interesting in those tunnels that are already open to traffic and whose lighting installations need to be renewed.
The economic, energy and environmental impact of tunnel lighting installations is enormous. A tunnel that is not excessively long can have a bill of several hundred thousand euros per year in lighting consumption, to which must be added the effect on the consumption of raw materials, the cost of the installation and derived greenhouse gas emissions. for the manufacture and installation of the hundreds of projectors needed in each tunnel.
The above figures become truly worrying if we take into account that, in the Spanish road network alone, there are more than 500 tubes without counting the underground passages, which depend on local administrations. It is, therefore, a problem of great magnitude.
Paradoxically, the energy consumption of the tunnels is much higher during the day than at night, since during daylight hours, lighting levels must be especially high to achieve good visual adaptation for drivers. If there were a sudden change from a sunny exterior to a poorly lit interior, the reduction in visual capacity due to the slow adaptation of the human eye would be unbearable if we take into account that a vehicle traveling at 100 km/h is traveling almost 28 meters per second. This means that the slightest delay in visual reaction time would result in tens of meters of uncontrolled advance.
The solution to achieve an acceptable visual adaptation consists in providing the tunnels with a powerful lighting installation, especially in the first hundred meters and which works at maximum power during the hours of high external light. The problem with this solution is the well-known impact mentioned above.
There are currently research groups in several countries that are actively working on strategies to reduce energy consumption in tunnel lighting installations. The solutions that are beginning to be implemented range from the introduction of sunlight inside the tunnels to the afforestation of the inlets with certain plant species with a low coefficient of reflection in sunlight, through the gradual introduction of LED projectors in those sections of the tunnel in which it is possible and viable (not all). As a result of these investigations, the lighting installations in many tunnels are currently being renovated.
These renovation operations require a prior evaluation of the lighting needs of the tunnel, which in many cases have changed since it was opened to traffic. To carry out these evaluations, it is necessary to have very precise images of the tunnel portal taken under controlled conditions and stipulated by current regulations. However, the requirements of the standards regarding the light evaluation of tunnels in operation are very difficult to implement accurately and in safe conditions for the operators.
An easy method to implement
Research carried out by UGR professors Antonio Pena and Juan Carlos Lopezproposes a rigorous but easily implemented method that establishes the methodology for the use of this type of photographs taken from vehicles or even from Internet maps (for example, Google Street View), so that the calculation method is equivalent to that of specified in the regulations for images taken under tightly controlled conditions.
The impact on the safety of workers and on the precision of the calculations (currently, due to traffic, approximations are taken that give rise to considerable errors), is very positive and makes it possible to address the necessary renovation operations with guarantees. lighting installations in tunnels.
“This is very important in tunnels that are already open to traffic and whose lighting installations need to be renewed,” explains the main author of the study, UGR professor Antonio Pena Garcia-. This is becoming more and more frequent due to the gradual entry of LEDs into tunnel lighting. Since the operators cannot take clear photos from a distance and at a height strictly determined by the standard, aiming at a specific point at the entrance of the tunnel and in the center of the road due to the enormous danger that this entails, currently these photographs are taken from the shoulder (also very dangerous) and from approximate distances with the consequent error. Our methodology provides some rescaling factors that convert the photos taken from vehicles in tunnels already open to traffic into equivalents to those recommended by the standard”.