Re: How do road flares work?

Road flares are just a variation on pyrotechnic devices.  All are made up 
of an oxidant (to supply oxygen), fuel, and inert filler.  They differ in 
the amount of each.  These devices can also have minerals added to them to 
produce colors.

In a road flare, the red color is produced by strontium compounds, 
normally the nitrate.  The mixute of fuel, fillers, and oxidant varies 
dependending on the type of flare.  I have recently seen cheap flares that 
have very little fuel and oxidant and burn cool.  Other flares will burn 
hot depending on the blend.  The speed depends on the oxidant level.  
Think about a piece of wood.  When you blow on it (more oxidant, it burns 
faster.  If you need more info, look in books on fireworks.