The use of DRL increases fuel consumption. Obviously, when the lights are switched on, a bigger load is placed on the dynamo. However, there is a large difference between using the customary dipped headlights and using low-energy LED lights. We will first take a look at the customary dipped headlights. Although the extra consumption due to switching on the dipped headlights is the same per car (2x55W), the relative differences are large.
A fuel efficient car using 6.7 litres per 100 km (1:15) with DRL by using dipped headlights has an extra consumption of 3%. A 10 litres per 100 km (1:10) car, for example, uses 2% more, and a lorry using 33 litres per 100 km uses 1% more (ETSC, 2003).
At the same time, increased fuel consumption causes an increased emission of harmful materials which is bad for the environment. The CO2 emissions of car traffic would increase by 0.6-1.4% (Elvik et al., 2003). Saving fuel and reducing CO2 emissions can be achieved for more than 50% by using special DRL lamps (21W per lamp) and for 90% by using LED (about 5W per lamp).
Another disadvantage of using conventional dipped headlights for DRL is that headlamps burn out faster, because they are switched on longer. This problem is only small if LED lamps are used.
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