In addition to rearview radar functions, the RTL515 also works as a tail light. During the daytime it be seen up to a mile away. It also includes ‘peloton mode’, providing a low-intensity flash that is easier on other cyclists’ eyes while riding in a group. The Varia RTL515 can last up to 16 hours on ‘day flash mode’ and 6 hours on ‘night flash’ or ‘solid’ mode.