A set of bike lights is essential for riding at night and in other conditions where visibility is poor or it is generally dark. There are two main types of front lights - those which help you be seen, and those to see by. With developments in LED technology over the past few years even lights for city riding are a lot brighter than they used to be, but if you want a light to see by either on unlit country roads or off-road routes, look to higher powered options like those made by Exposure. Road and off-road specific options are available to suit all types of riding.
For rear lights, look out for convenient mounting options, different brightness or flash modes and long battery life.