1 – Power consumption within the vehicle becomes higher. This gives a comparatively higher load to the magneto/alternator, which is transferred to the crankshaft. Consequentially there will be a drop in mileage in the vehicles with this type of AHO, by as much as 1 kmpl. This is in case of halogen bulb for low beam. After a year or two, when every vehicle (especially two-wheeler) on road has around 1 kmpl drop due to wear & tear, the collective consequence of burning more fuel could really high.
2 – In India the duration of vehicle idling is significant due to excessive traffic. If the reflector dome within the headlamp is not redesigned, the prolonged high heat from the bulb will cause the reflector to fade and deteriorate much earlier, especially during vehicle idle condition. This consequence will be more negligible when LED DRL is tuned to be AHO.
3 – AHO would be more useful on highways than in city. In cities with dense traffic, AHO seems less needed.
4 – If the vehicle doesn’t have the throw/angle of low-beam adjusted properly, it will cause irritation to the pedestrians and on-coming drivers. This has the potential to cause accidents. In case of an LED DRL, such an incident is less likely to happen.
5 – There is another potential disaster that could be accelerated by AHO in India – Global Warming. After a year or two, when most of the vehicles in the city would have the halogen lamps always lit, think of the collective heat that will be emitted. At a traffic signal, where heat radiation is already felt high, those hundreds of vehicles would contribute to much higher heat because of always ON halogen lamp. This will accelerate the rise in temperature of the region.
6 – In European countries, as said before, DRL was implemented as the weather is foggy most of the time. India is a very diverse country. Foggy roads are witnessed mostly in North India and rarely in South India. This is why Solar Farms are setup mostly in the central and southern part of the country, given the closer vicinity to the equator and brighter days. So, AHO will have good purpose in the North, but not at all in the South.
7 – When the battery of the vehicle is down, or when the fuel is very low, the user may not be able to crank the vehicle as many times as he would be able to in a vehicle that doesn’t have Always ON Headlamp with halogen bulb. For instance, if you could crank the engine 10 times before, with AHO, you would be able to crank the engine only 7-8 times now. This is just a vague example.