In this section we shall use a narrow definition of Traffic Engineering. Here we shall look at the vehicular traffic on roadways. We shall study in traffic engineering how to analyze vehicular traffic on roadways and how to design various facilities which aid in the smooth flow of traffic.

First, however, we shall recapitulate some things we learnt in Transportation Engineering I

	L1 L2
Figure-1: A two lane one-way road where L1 and L2 are two lanes.

In the above example there are two streams moving in the same direction. This type of road is called a one-way road.

	L1 L2
Figure-2 : A two lane two-way road where L1 and L2 are two lanes.

This is a two way road; the streams move in opposing directions. Strict adherence to lanes is referred to as maintaining proper lane discipline. In India often drivers do not maintain proper lane discipline.

Let us now look at Vehicles A and B in Figure3 (press the arrow button). Let us also assume that distance of a vehicle is measured from the line marked L-L. Let us also assume that time = 0, when vehicle A is at L-L. Hence as vehicles move up they trace a path on a corresponding Time-Distance plot.

Similarly, if we trace the path of many vehicles, we get a distance-time plot, as shown in Figure 5. The figure also explains various other traffic engineering terms.