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Passenger Car Unit (PCU) is a metric used in Transportation Engineering, to
assess traffic-flow rate on a highway.
A Passenger Car Unit is a measure of the impact that a mode of transport has on
traffic variables (such as headway, speed, density) compared to a single
standard passenger car.
This is also known as passenger car equivalent.
For example, typical values of PCU (or PCE) are:
Table 1:
Values of PCU
| Car |
1.0 |
| Motorcycle |
0.5 |
| Bicycle |
0.2 |
| LCV |
2.2 |
| Bus, Truck |
3.5 |
| 3-wheeler |
0.8 |
|
Highway capacity is measured in PCU/hour daily.
The table below shows the volumetric data collected at an intersection:
Calculate the peak hour volume, peak hour factor (PHF), and the actual (design)
flow rate for this approach.
Table 2:
Volumetric data collected
| From |
To |
HCV |
LCV |
CAR |
3W |
2W |
| 2.30 |
2.40 |
4 |
10 |
6 |
38 |
24 |
| 2.40 |
2.50 |
8 |
12 |
9 |
63 |
33 |
| 2.50 |
3.00 |
7 |
13 |
8 |
42 |
27 |
| 3.00 |
3.10 |
6 |
13 |
15 |
37 |
32 |
| 3.10 |
3.20 |
7 |
14 |
10 |
51 |
28 |
| 3.20 |
3.30 |
6 |
10 |
9 |
63 |
41 |
| 3.30 |
3.40 |
8 |
11 |
8 |
48 |
38 |
| 3.40 |
3.50 |
10 |
6 |
15 |
47 |
21 |
| 3.50 |
4.00 |
9 |
7 |
9 |
54 |
26 |
| 4.00 |
4.10 |
10 |
9 |
11 |
62 |
35 |
| 4.10 |
4.20 |
12 |
11 |
12 |
61 |
39 |
| 4.20 |
4.30 |
8 |
8 |
10 |
54 |
42 |
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The first step in this solution is to find the total traffic volume for each 15
minute period in terms of passenger car units.
For this purpose the PCU values given in the table are used. Once we have this,
we can locate the hour with the highest volume and the 15 minute interval with
the highest volume.
The peak hour is shown in blue below with the peak 15 minute period shown in a
darker shade of blue.
Table 3:
Solution of the problem
| From |
To |
Flow in PCU |
| 2.30 |
2.40 |
84.4 |
| 2.40 |
2.50 |
130.3 |
| 2.50 |
3.00 |
108.2 |
| 3.00 |
3.10 |
110.2 |
| 3.10 |
3.20 |
120.1 |
| 3.20 |
3.30 |
122.9 |
| 3.30 |
3.40 |
117.6 |
| 3.40 |
3.50 |
111.3 |
| 3.50 |
4.00 |
112.1 |
| 4.00 |
4.10 |
132.9 |
| 4.10 |
4.20 |
146.5 |
| 4.20 |
4.30 |
119.8 |
|
The peak hour volume is just the sum of the volumes of the six 10 minute
intervals within the peak hour (743.6 PCU).
The peak 10 minute volume is 146.5 PCU in this case.
The peak hour factor (PHF) is found by dividing the peak hour volume by four
times the peak 10 minute volume.
The actual (design) flow rate can be calculated by dividing the peak hour
volume by the PHF,
 , or by multiplying the peak 10
minute volume by six,
 .
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