You can also view previously answered questions in the HSW Question Archive . For several years now Canada has required all new cars sold to have daytime running lights. Any time the car is running the headlights are on, but the taillights and other lights are off. You have to turn on these other lights from the dashboard at night. The US has not adopted this law, but if it did they would definitely consume gasoline.
Headlights require power, and a car's engine produces power using gasoline.
If you make a few assumptions, it is possible to estimate how much gas the law would consume. Let's say the daytime running lights use 100 watts since there are two bulbs. To calculate the energy used, we need to figure out how much time people will spend with their lights on. We need to make a guess at the average speed people drive including stops in order to figure out how much time people spent driving their cars. Let's guess 30 mph, which means each mile takes two minutes.