Final answer:
Tankers can turn over at the posted speed limits on curves due to tire friction and steeply banked curves.
Step-by-step explanation:
Tankers can turn over at the posted speed limits on curves because of the tire friction that enables vehicles to take the curve at higher speeds than the ideal speed. Some curves on race tracks and test tracks are steeply banked, which further assists in allowing vehicles to take curves at very high speeds.