It is the law in NSW that all bike riders have the following in low light or hazardous conditions :
(a) a flashing or steady white light that is clearly visible for at least 200 metres from the front of the bicycle, and
(b) a flashing or steady red light that is clearly visible for at least 200 metres from the rear of the bicycle, and
Thanks to LED technically, the brightness and range of bike lights has really increased. You can pick up a bike light reasonably priced, that will do the job.
If you are riding in places with no street lights at night, such as rural roads, we encourage you to have a bright enough light that you could see potholes, animals or any other obstacles.
Also, remember to keep your lights charged or carry a spare set with you.