Road flares are an extremely bright light source that can be found all over the map. Road flares can attract zombies from large distances. Players can also see the light from a flare from far away. When used carefully, they can be used to distract both survivors and zombies.
An additional use for road flares is countering players using NV Goggles. Any source of bright light can temporarily blind someone using night vision goggles. Since road flares are so bright, they can instantly blind any night vision user, with the effect persisting even after the NV Goggles are taken off.