Highway Engineering

The Design of Highway Intersections 115

Example 5.2 Contd

Estimate the ratio of flow to capacity for each of the opposed movements
and, for the one with the highest ratio, estimate the average queue length and
delay per vehicle during the peak hour.

Geometric parameters:

The width of the major carriageway (W) is 9.5 m.

The lane widths for traffic exiting the minor road turning both left and right
(wba,wbc) are 2.5 m.

The lane width on the major road for traffic waiting to turn right onto the
minor road (wcb), is 2.2 m.

Visibility to the right and left for traffic exiting the minor road turning right
(Vrba,Vlba) is 30 m and 50 m respectively.

Visibility to the right for traffic exiting the minor road turning left (Vrbc) is
30 m.

Visibility to the right for traffic exiting the major road, turning right onto the
minor road (Vrcb) is 50 m.

Solution

When using Equations 5.1 to 5.3 for estimating the ratios of flow to capac-
ity for the various opposed turning movements, the design reference flows
shown in Fig. 5.13 should be multiplied by 1.125 in order to allow for short-
term variations in the traffic flow. (These short-term variations are allowed
for in PICADY.)

Factored flows:
qab=169 (150 ¥1.125)

qac=619 (550 ¥1.125)

qca=844 (750 ¥1.125)

qcb= 84 (75 ¥1.125)

qba=197 (175 ¥1.125)

qbc=141 (125 ¥1.125)

Contd