If the angle of merging is low, then the relative speed will be ______

What is the most vulnerable part of the traffic?

The specifications for road signs are specified by ______

The speed at which the value of time headway is lowest represents the ______

The traffic population is estimated by ______

In trial cycle method, the average time headway is assumed as ______

If the velocity of a vehicle is 60kmph and the other vehicle velocity is 20kmph, then the relative velocity is?

In traffic engineering, the elements are classified into how many categories?