With the growing number of private vehicles, there is an increasing concern about traffic congestion and pollution problems resulting from cars.
You begin with the general description of "private vehicles" and end with refering specifically to "car".
Some believe that increasing the price of petrol is the most effective way
to reduceof solving those problems
To begin with, it is undeniable that imposing a high fuel price may reduce the number of private car users.
it's the usage that gets affected, not the number of users...pay more attention to the alignment with the topic;To begin with, it is undeniable that higher petrol prices discourage people to use their private cars.
You display very good writing skills.... make sure you keep a good alignment with the topic throughout your essay :)