The Izzard Equation for calculation of roadway flows is often presented without any explanation of its derivation or any justification for its likely accuracy. It is in fact the familiar Manning Channel Flow Formula applied to a channel of triangular shape. For that reason channel roughness coefficients to be used are the familiar Manning coefficients.
This bulletin looks at the derivation of this equation and gives a solution for calculation of flows for the roadway cross section shown above.
To read more or download Roadway Flow – Technical Bulletin No 6, click on the link below.
