The Power of Points
Tank trucks have rounded ends so that loads do not accumulate at one end.
More than two hundred years ago, scientists observed that a conductor with a pointed region on its surface hardly remains electrified, as the electrical charge supplied to it escapes through this tip. However, those scientists did not have a satisfactory explanation for the fact.
Today we know that the power of the spikes occurs because, in an electrified conductor, the charge tends to accumulate in the sharp regions. As a result, the electric field in these regions is stronger than in the flatter regions of the conductor.
It is due to this fact that it is not recommended, on rainy days, to take shelter under trees and in higher places.
In the case of tank trucks, their Ca, preventing a spark from being generated, which would cause a large explosion.