A simple mathematical model for how traffic flows along a road is introduced. The resulting first-order ordinary differential equations can be used as an application of solution techniques taught at A-level and first year undergraduate level, and as a motivator to encourage students to think critically about the physical interpretation of the results which the equation produces.
McCartney, M., & Carey, M. (1999). Modelling traffic flow: Solving and interpreting differential equations. Teaching Mathematics and its Applications, 18(3), 115-121. https://doi.org/10.1093/teamat/18.3.115