Active travel for the home to school commute is an ideal opportunity to improve pupils physical activity levels. Many studies have looked at how pupils travel to school and the motivating factors behind these decisions. This paper applies an innovative methodology to model each pupil’s individual route to school and then evaluates how different policy changes could increase the uptake of active travel. The changes are quantified in terms of the proportion using active travel, CO2 emissions and criterion distances- a method of measuring how far pupils are willing to travel using a certain mode of transport. Findings suggest that the greatest reduction in CO2 and increase in health benefits can be made by encouraging more primary school pupils to use active travel and targeting schools with existing low levels of active travel.