The hypothesis that cars with reflective sunshades have the lowest interior temperature, is proven to be true.
The use of sunshades inside a car on bright sunny days hels to reduce temperatures by about 8 to 10 °C. They certainly make quite a difference! Besides helping to keep the cabin at comfortable temperatures, they also help to protect our car’s interior from discoloration and cracking.
What would happen if the experiment were to be repeated by using cars with tinted glass?
The experiment can also be repeated by using cars with different colors and sunshades.
Is your car an oven? - http://www.roadandtravel.com/autonewsandviews/2005/sunshades.htm
Cool your wheels - http://editorial.autos.msn.com/article.aspx?cp-documentid=434615
Ensure that cars are driven by persons with valid driving licenses.