Highway Engineering

108 Highway Engineering

Ghost island

Single lane

dualling

Simple

Roundabout

8000

7000

6000

5000

4000

3000

2000

1000

5000 15000 10000 20000

Minor road flow (2-way AADT)

Major road flow (2-way AADT)

Figure 5.5Different levels of priority intersections for various major and minor road

flows in the design year.

Example 5.1 – Determination of flows at a priority intersection

An existing simple major/minor priority junction at the intersection of two

single carriageway 2-lane roads is to be upgraded. The major route is a major

interurban highway. Figure 5.6 shows the annual average daily traffic

(AADT) flow ranges predicted for each of the arms to the intersection in the

design year, assumed in this case to be 15 years after opening.

Taking the upper AADT flows of 10 250 for the major carriageway and

3 000 on the minor carriageway, Fig. 5.5 indicates that the junction must

7500 to 10,250 AADT

Minor road

2-lane single

Major road 2-lane single carriageway

7500 to 10,250 AADT

2,000 to 3,000 AADT

N

Figure 5.6AADT 2-way flows.

Contd