Ow do the cars effect the CO2 level of the air.

IB Environmental Systems IA. Basically I measured the level of CO2 in 2 busy areas: Car park and the school exit, here are the results:
Car park: 1)182 ppm 2)92 3)73 4)55 5)54
School exit: 1) 84 2)62 3)36 4)30 5)35
Here are the pictures of the plan: