What's in a road flare?

Search: road flare

Why: Just saw a little part of one between lanes on the freeway, still blazing.

Answer: Road flares (also called highway flares or ground flares) are known as fusees, and burn 10-60 minutes with a bright red light. Flares produce light through the combustion of a pyrotechnic composition. The ingredients are varied, but often based on strontium nitrate, potassium nitrate, or potassium perchlorate and mixed with a fuel such as charcoal, sulfur, sawdust, aluminium, magnesium, or a suitable polymeric resin. Flares may be colored by the inclusion of pyrotechnic colorants. Calcium flares are used underwater to illuminate submerged objects.

Source: Wikipedia

The More You Know: In the days before train radio communications, fusees were used to keep trains apart on un-signaled lines. A railroad fusee was timed to burn for 10 minutes and then dropped on the tracks behind a train. If a following train encountered a burning fusee, it was not to pass until the fusee burned out. Fusees made specifically for railroad use have a sharp steel spike at one end, used to embed the fusee upright in a wooden railroad tie.