An additional disadvantage compared with halogen or LED lights is that the HID lamp does not tolerate repeated strikes, and in many cases does not relight immediately after shutting down. Likewise, should the battery level fall too low, the lamp will shut down rather than dimming. But the longer battery life than halogens tends to negate these problems, as many riders simply switch the light on and leave it running throughout the ride. If using a HID lighting system on the road, lights should be adjusted to avoid dazzling oncoming traffic. The only real advantage to these is that they are often omnidirectional, a quality useful in running lights which must be visible through a very wide arc. Newer LED lights have this feature, removing even this final advantage. Energizer once made a 2.4W halogen rear lamp, which was essentially a headlamp with a red lens, but most rear lights only need to be around 0.5W. Most LED lights will work in either flashing or steady modes. Some LED lights have multiple banks of LEDs allowing both flashing and steady light at once. This can also be achieved by having one flashing light and one steady one. In many countries, LED flashers are the norm for rear lights. In others such as Germany and the Netherlands flashing lights are forbidden by law. In the UK flashing LEDs (front and rear) are legal from October 2005, provided that the lights conform to the requirements of the current Road Vehicles Lighting regulations. Many vendors claim EU compliance, however, this provides no consistent safety or legal value across the Union. The most common power source for rear LEDs is a set of alkaline cells and rechargeable cells. In both cases the battery tends to fail quickly when it goes; it is widely considered a good practice to have two rear lights in case a battery fails en route. "Advantages of LED rear lights"  An innovation in bicycle lighting, though common in industrial applications, xenon strobes are brighter than LEDs and are used by some as rear lights. "Advantages of xenon strobes"  "Disadvantages"  The introduction of the Low self-discharge NiMH battery (LSD-NiMH) in 2005 made rechargeable AA and AAA sized batteries more viable for powering LED bicycle lights. Previously, the self-discharge effect of NiCAD and NiMH batteries caused the battery to run down over a period of weeks or a few months, even when not in use. This was particularly a problem for low powered LED lights, and for users who only used their bicycle lights occasionally.