A broad comparison of Passenger car unit for Indian and American traffic conditions

1. Comparison of Passenger Car Equivalent (Passenger Car Unit)
on Urban Arterial Roads between India (Chennai & Mumbai)
and U.S. (Lincoln, NE)
Jianan Zhou (UNL), Noorul Sharik (IITM) ,
Priyanka (IITM), Raghupathi Kandiboina (IITB)
April 25, 2016

2. Content
Introduction
Methodology for PCE determination
Data Collection
PCE Calculation
Comparison Analysis
Conclusion
1
2
3
4
5
6

3. 1. Introduction
Definition of Passenger Car Equivalent (Passenger Car Unit)
• A Passenger Car Equivalent is essentially the impact that a mode of
transport has on traffic variables (such as headway, speed, density)
compared to a single car.
• PCE plays a crucial role in capacity analysis.
• In U.S., the term “PCE” is used, while in India, the term “Passenger Car
Units” (PCU) is used instead of “PCE”.

4. 1. Introduction
Research Objective
• Focus on PCE of trucks (for India: HCV; for U.S.: single + heavy truck)
• Compare PCEs at midway on urban arterial roads between India (Chennai)
and U.S. (Lincoln, NE)
• Compare PCEs at intersections on urban arterial roads between India
(Mumbai) and U.S. (Lincoln, NE)
• Give recommended PCE value for midway and intersection on urban arterial
roads in India and U.S.

5. 1. Introduction
Research Procedure and Task
• Task 1: Literature review for different PCE determination method
- after that, we find using headway, delay and speed-area
method to calculate PCE in this research
• Task 2: Data collection
• Task 3: PCE calculation
- Headway and speed-area method for PCE at midway
- Delay and speed-area method for PCE at intersection

6. Research Procedure and Task
• Task 4: Statistical analysis for PCE comparison
- Midway during off-peak/peak hour between U.S. and India
- Intersection during off-peak/peak hour between U.S. and India
- Midway during all time between U.S. and India
- Intersection during all time between U.S. and India
1. Introduction
• Task 5: Discussion and draw conclusion

7. Content
Introduction
Methodology for PCE determination
Data Collection
PCE Calculation
Comparison Analysis
Conclusion
1
2
3
4
5
6

8. Headway-based Methodology
2. Methodology for PCE Determination
𝐻 − 𝑃𝐶𝐸 =
1 − 𝑝) ℎ 𝑝𝑡
+ ℎ 𝑡𝑝 − ℎ 𝑝𝑝) + 𝑝 ∗ ℎ 𝑡𝑡
ℎ 𝑝𝑝
≈
ℎ 𝑡.
ℎ 𝑝.
where:
𝑝= percentage of trucks at a mixed traffic stream;
ℎ 𝑝𝑡 = Mean headway in seconds for passenger cars following trucks;
ℎ 𝑡𝑝 = Mean headway in seconds for trucks following passenger cars ;
ℎ 𝑝𝑝= Mean headway in seconds for passenger cars following passenger cars ;
ℎ 𝑡𝑡 = Mean headway in seconds for trucks following trucks;
ℎ 𝑝. = Mean headway in seconds for passenger cars following passenger cars or trucks;
ℎ 𝑡. = Mean headway in seconds for trucks following passenger cars or trucks.
*This method was proposed by Krammes in 1986. Until now, it has been used in PCE determination
at highway and freeway in U.S., but has not been used in India. Theoretically, this method performs
well for conditions that vehicles strictly following lane disciplines.

9. Delay-based Methodology
2. Methodology for PCE Determination
where:
∆𝑑 𝑡= additional delay caused by per truck
𝑑0= average delay per vehicle of passenger car when truck percentage is 0%(base delay)
𝑛 𝑡= number of truck in mixed queue in one cycle
𝑗= position of vehicle in mixed queue in one cycle
𝑝, 𝑚= position of first truck and last vehicle in mixed queue in one cycle
𝑇𝑇𝑗
𝑡
, 𝑇𝑇𝑗
0
= travel time for jth vehicle in mixed queue and in all passenger cars queue
𝐷 − 𝑃𝐶𝐸 = 1 +
∆𝑑 𝑡
𝑑0
= 1 +
𝑗=𝑝
𝑚
𝑇𝑇𝑗
𝑡
− 𝑇𝑇𝑗
0
𝑛 𝑡 𝑑0
*This method was proposed by Zhao in 1996. Until now, it has been used in PCE determination at
intersection in U.S., but has not been used in India. Theoretically, this method performs well for
conditions that vehicles strictly following lane disciplines and high speed difference between trucks
and passenger cars.

10. Speed-area Methodology
2. Methodology for PCE Determination
𝑆𝐴 − 𝑃𝐶𝐸 𝑆𝐴 − 𝑃𝐶𝑈) =
𝑉𝑐 𝑉𝑡
𝐴 𝑐 𝐴 𝑡
where:
𝑉𝑐 = Mean speed for passenger cars
𝑉𝑡 = Mean speed for trucks
𝐴 𝑐 = Projected rectangular areas (length*width) on the road for passenger cars
𝐴 𝑡 = Projected rectangular areas (length*width) on the road for trucks
*This method was proposed by Chandra in 2000. Until now, it has been used in PCE determination
at highway and intersection in India, but has not been used in U.S. Theoretically, this method
performs well for conditions that vehicles do not following lane disciplines.

11. Summary for Methodology
2. Methodology for PCE Determination
Headway Method → H-PCE at midway for India and U.S.
Delay Method → D-PCE at intersection for India and U.S.
Speed-area Method → SA-PCE at midway and intersection
for India and U.S.
Longitudinal Effects
(effects on followers)
Lateral Effects
(effects on adjacent
vehicles)

12. Content
Introduction
Methodology for PCE determination
Data Collection
PCE Calculation
Comparison Analysis
Conclusion
1
2
3
4
5
6

13. Data Collection Time, Duration and Location
3. Data Collection
Country Location Time Duration Remark
India Midway - Chennai Off-peak 2 hours One direction, 7:00 am to 9:00 am
India Midway - Chennai Peak 2 hours One direction, 9:00 am to 11:00 am
U.S. Midway- Lincoln, NE Off-peak 2 hours One direction, 2:00 pm to 4:00 pm
U.S. Midway- Lincoln, NE Peak 2 hours One direction, 5:00 pm to 7:00 pm
India Intersection-Mumbai Off-peak 2 hours
Signalized intersection, one approach, through movement,

14. Data Collection for Midway in India (Chennai)
3. Data Collection
• Data Collection Site:
- Tidal Park
• Data Collection Device:
- Infra-Red Traffic Logger (TIRTL)
• Collected Data:
- Traffic volume, instantaneous
speed, leading and lagging headway
data, vehicle type, length and width of
vehicles, percentage of trucks

15. Data Collection for Intersection in India (Mumbai)
3. Data Collection
• Data Collection Site:
- Vashi Rd & Jambul Marg
(Intersection on urban arterial roads)
• Data Collection Device:
- Video camera + manual + Timer
• Collected Data:
- Traffic volume, clearance time, clearance
length, vehicle type, length and width of vehicles,
red/green signal length, cycle length

16. Data Collection for Midway in U.S. (Lincoln, NE)
3. Data Collection
• Data Collection Site:
- S 84th Rd (urban arterial roads)
• Data Collection Device:
- Video camera + Video detectors
• Collected Data:
- Traffic volume, instantaneous
speed, leading and lagging headway
data, vehicle type, vehicle length,
percentage of trucks
Video Detectors

17. Data Collection for Intersection in U.S. (Lincoln, NE)
3. Data Collection
• Data Collection Site:
- N 27th Rd & Cornhusker Hwy
(Intersection on urban arterial roads)
• Data Collection Device:
- Video camera + Video detectors
• Collected Data:
- Traffic volume, instantaneous speed,
headway, vehicle type, vehicle length,
red/green signal length, cycle length
Video Detectors

18. Content
Introduction
Methodology for PCE determination
Data Collection
PCE Calculation
Comparison Analysis
Conclusion
1
2
3
4
5
6

19. PCE Calculation for Midway
4. PCE Calculation
• Method:
- Headway and Speed-area method for both India and
U.S. for both off-peak and peak hours
• Aggregation Interval:
- PCEs are calculated every 10 minutes, and 12
observations for each combination of time, location and
method, 8 combinations and 96 observations in total.

20. PCE Calculation for Midway
4. PCE Calculation
observation
PCE-Midway
Off-peak hour Peak hour
India(2h) America(2h) India(2h) America(2h)
Speed-area Headway Speed-area Headway Speed-area Headway Speed-area Headway
1(0-10min) 1.70 1.82 1.16 1.52 2.48 3.40 1.12 1.90
2(11-20min) 1.59 3.42 1.24 1.96 1.78 2.17 1.22 1.56
3(21-30min) 1.62 2.96 1.14 1.57 2.04 2.52 1.37 1.99
4(31-40min) 1.91 2.47 1.16 1.56 1.95 2.40 1.12 1.79
5(41-50min) 1.25 1.50 1.16 1.68 2.75 2.53 1.14 1.77
6(51-60min) 1.80 2.90 1.38 1.78 2.78 2.45 1.20 1.90
7(61-70min) 1.55 3.56 1.26 1.97 1.45 2.83 1.13 1.56
8(71-80min) 1.64 2.15 1.24 1.94 2.34 3.20 1.14 1.32

21. PCE Calculation for Midway
4. PCE Calculation
0
0.5
1
1.5
2
2.5
3
3.5
4
4.5
5
5.5
6
6.5
PCE
Observation
PCE at Midway by Headway Method
Off-peak, India Off-peak, U.S. Peak, India Peak, U.S.
0
0.5
1
1.5
2
2.5
3
3.5
4
4.5
5
5.5
PCE
Observation
PCE at Midway by Speed-area Method
Off-peak, India Off-peak, U.S. Peak, India Peak, U.S.

22. Summary of PCE Calculation for Midway
4. PCE Calculation
• Difference in PCEs between off-peak and peak hours in
both India and U.S. by both method may not be obvious.
• PCEs in India may be higher than U.S.
• There are more variance in PCEs in India than in U.S.
• Difference between headway-based PCEs and speed-
area-based PCEs may not be obvious for both India and
U.S.

23. PCE Calculation for Intersection
4. PCE Calculation
• Method:
- Delay and Speed-area method for both India and
U.S. for both off-peak and peak hours
• Aggregation Interval:
- PCEs are calculated every 4 cycles, and 11
observations for each combination of time, location and
method, 8 combinations and 88 observations in total.

24. PCE Calculation for Intersection
4. PCE Calculation
Observation
(every 4
cycles)
PCE-Intersection
Off-peak hour Peak hour
India(2h) America(2h) India(2h) America(2h)
Speed-area-4 Delay-3 Speed-area-2 Delay-1 Speed-area-8 Delay-7 Speed-area-6 Delay-5
1(1-4) 5.36 1.24 4.8 1.41 5.26 1.28 4.92 1.84
2(5-8) 3.91 1.20 4.86 1.34 5.53 1.36 4.82 1.87
3(9-12) 3.88 1.22 4.76 1.32 5.78 1.42 4.85 1.61
4(13-16) 5.29 1.37 4.73 1.49 5.44 1.46 4.87 1.73
5(17-20) 7.16 1.91 5.00 1.60 6.03 1.64 4.85 1.85
6(21-24) 6.27 1.44 4.94 1.38 6.56 1.48 5.00 2.11
7(25-28) 5.77 1.11 5.04 1.66 5.21 1.26 4.90 1.46
8(29-32) 7.63 1.25 4.98 1.98 2.64 1.19 4.91 2.11
9(33-36) 4.29 1.16 4.8 1.58 4.41 1.22 4.84 1.52
10(37-40) 6.33 1.54 4.77 1.47 7.29 1.63 4.8 1.93
11(41-44) 6.84 1.64 4.91 1.67 5.02 1.74 4.85 1.65

25. PCE Calculation for Intersection
4. PCE Calculation
0.8
1
1.2
1.4
1.6
1.8
2
2.2
2.4
PCE
Observation
PCE at Intersection by Delay Method
Off-peak, India Off-peak, U.S. Peak, India Peak, U.S.
2
2.5
3
3.5
4
4.5
5
5.5
6
6.5
7
7.5
8
PCE
Observation
PCE at Intersection by Speed-area Method
Off-peak, India Off-peak, U.S. Peak, India Peak, U.S.

26. Summary of PCE Calculation for Intersection
4. PCE Calculation
• For delay method, difference in PCEs between off-peak and
peak hours in India may not be obvious, but it may be obvious
in U.S; also, delay-based PCEs during peak hours in U.S. may
be higher than that in India.
• For speed-area method, there are more variance in PCEs in
India than in U.S; also, difference in speed-area-based PCEs
between off-peak and peak hours in U.S. may not be obvious.
• PCEs calculated by speed-area method may be much higher
than PCEs calculated by delay method in both India and U.S.

27. Box Plot for PCE Calculation
4. PCE Calculation

28. Content
Introduction
Methodology for PCE determination
Data Collection
PCE Calculation
Comparison Analysis
Conclusion
1
2
3
4
5
6

29. Introduction for Statistical Comparison Analysis
5. Comparison Analysis
• Experimental units:
- PCE. PCEs at midway and intersection are separately
compared.
• Treatment design:
- Three factors (hour, country and method) with 2
levels in each factor (hour: off-peak and peak; country:
India and U.S.; method: headway/delay, speed-area).
- 8 treatments in total.
- Analyze by SAS.

30. Statistical Comparison Analysis for PCE at Midway
5. Comparison Analysis
• Test effect of hour, country and method
Type III Tests of Fixed Effects
Effect Num DF Den DF F Value Pr > F
hour 1 88 2.15 0.1459
country 1 88 78.81 <.0001
hour*country 1 88 1.72 0.1925
method 1 88 24.96 <.0001
hour*method 1 88 5.73 0.0188
country*method 1 88 0.33 0.5667
hour*country*metho
d
1 88 8.30 0.0050
*Three–way interaction of hour, country and method is significant.
*Values of PCE may be affected by “hour”, “country” and “method”
three factors.

31. Statistical Comparison Analysis for PCE at Midway
5. Comparison Analysis
• Compare PCEs in India and America for off-peak hours
Estimates
Label Estimate Standard Error DF t Value Pr > |t|
America vs India, offpeak,
headway
-1.2608 0.2288 88 -5.51 <.0001
America vs India, offpeak,
speedarea
-0.4700 0.2288 88 -2.05 0.0429
*Both headway-based and speed-area-based PCEs in India are
significantly higher than in U.S. during off-peak hours.
*During off-peak hours, trucks in India have more longitudinal and
lateral effects on other vehicles than in U.S.

32. Statistical Comparison Analysis for PCE at Midway
5. Comparison Analysis
• Compare PCEs in India and America for peak hours
Estimates
Label Estimate Standard Error DF t Value Pr > |t|
America vs India, peak,
headway
-0.9021 0.2288 88 -3.94 0.0002
America vs India, peak,
speedarea
-1.4297 0.2288 88 -6.25 <.0001
*Both headway-based and speed-area based PCEs in India are
significantly higher than in U.S. during peak hours.
*During peak hours, trucks in India have more longitudinal and lateral
effects on other vehicles than in U.S.

33. Statistical Comparison Analysis for PCE at Midway
5. Comparison Analysis
• Compare PCEs in India and America for all hours
Estimates
Label Estimate Standard Error DF t Value Pr > |t|
America vs India, all,
headway
-1.0814 0.1618 88 -6.68 <.0001
America vs India, all,
speedarea
-0.9498 0.1618 88 -5.87 <.0001
*Both headway-based and speed-area based PCEs in India are
significantly higher than in U.S. for all hours.
*During all hours, trucks in India have more longitudinal and lateral
effects on other vehicles than in U.S.

34. Statistical Comparison Analysis for PCE at Midway - Summary
5. Comparison Analysis
No matter during off-peak or peak hours, both headway-based and
speed-area-based PCEs of trucks at midway in India is higher than that
in U.S.;
On the other words, no matter during off-peak or peak hours, trucks at
midway in India have more longitudinal and lateral effect on other
vehicles than that in U.S.

35. Statistical Comparison Analysis for PCE at Intersection
5. Comparison Analysis
• Test effect of hour, country and method
Type III Tests of Fixed Effects
Effect Num DF Den DF F Value Pr > F
hour 1 80 0.00 0.9788
country
1 80 2.18 0.1436
hour*country
1 80 0.92 0.3410
method
1 80 723.79 <.0001
hour*method
1 80 1.32 0.2532
country*method
1 80 11.65 0.0010
hour*country*metho
d
1 80 0.05 0.8165
*Two–way interaction of country and method is significant; method is significant.
*Values of PCE may be affected by “country” and “method” , not affected by
“hour”.

36. Statistical Comparison Analysis for PCE at Intersection
5. Comparison Analysis
• Compare PCEs in India and America for off-peak hours
Estimates
Label Estimate Standard Error DF t Value Pr > |t|
America vs India, offpeak,
delay
0.1655 0.2733 80 0.61 0.5466
America vs India, offpeak,
speedarea
-0.8309 0.2733 80 -3.04 0.0032*During off-peak hours, speed-area-based PCEs in India are significantly higher
than in U.S.; while difference in delay-based-PCEs between India and U.S. is not
significant.
*During off-peak hours, trucks in India and U.S. have same degree of longitudinal
effect on other vehicles; while trucks in India have more lateral effect on other
vehicles than in U.S.

37. Statistical Comparison Analysis for PCE at Intersection
5. Comparison Analysis
• Compare PCEs in India and America for peak hours
Estimates
Label Estimate Standard Error DF t Value Pr > |t|
America vs India, peak,
delay
0.3636 0.2733 80 1.33 0.1871
America vs India, peak,
speedarea
-0.5055 0.2733 80 -1.85 0.0681*During peak hours, speed-area-based PCEs in India are significantly higher than in
U.S. (noticed: although p-value > 0.05, it is much closer to 0.05 than other difference);
while difference in delay-based-PCEs between India and U.S. is not significant.
*During peak hours, trucks in India and U.S. have same degree of longitudinal effect
on other vehicles; while trucks in India have more lateral effect on other vehicles than
in U.S.

38. Statistical Comparison Analysis for PCE at Intersection
5. Comparison Analysis
• Compare PCEs in India and America for all hours
Estimates
Label Estimate Standard Error DF t Value Pr > |t|
America vs India, all, delay 0.2645 0.1933 80 1.37 0.1749
America vs India, all,
speedarea
-0.6682 0.1933 80 -3.46 0.0009
*During all hours, speed-area-based PCEs in India are significantly higher than
in U.S.; while difference in delay-based-PCEs between India and U.S. is not
significant.
*During all hours, trucks in India and U.S. have same degree of longitudinal
effect on other vehicles; while trucks in India have more lateral effect on other
vehicles than in U.S.

39. Statistical Comparison Analysis for PCE at Intersection - Summary
5. Comparison Analysis
No matter during off-peak or peak hours, there is no difference in
delay-based PCE of trucks at intersection between India and U.S.;
On the other words, no matter during off-peak or peak hours, trucks at
intersection in India and U.S. have similar longitudinal effect on other
vehicles.
No matter during off-peak or peak hours, speed-area-based PCE of
trucks at intersection in India is higher than that in U.S. ;
On the other words, no matter during off-peak or peak hours, trucks at
intersection in India have more lateral effect on other vehicles than that
in U.S.

40. Content
Introduction
Methodology for PCE determination
Data Collection
PCE Calculation
Comparison Analysis
Conclusion
1
2
3
4
5
6

41. Conclusions for Research
6. Conclusion
• At midway, no matter during off-peak or peak hours, trucks in
India have more longitudinal and lateral effects on other
vehicles than that in U.S.
• At intersection, trucks in India have more lateral effects on
other vehicles than that in U.S. for both off-peak and peak
hour; however, trucks in India and U.S. have similar
longitudinal effect on other vehicles for both off-peak and peak
hour.

42. Recommended PCE Values based on Research
6. Conclusion
Midway Intersection
Headway Speed-area Delay Speed-area
U.S. 1.7 1.2 1.7 4.9
India 2.8 2.1 1.4 5.5

43. Our Works
6. Conclusion
• IITM:
- Data collection and PCE calculation for Midway, Chennai
• IITB:
- Data collection and PCE calculation for Intersection, Mumbai
• UNL:
- Data collection and PCE calculation for Lincoln, NE
• IITM, IITB and UNL:
- Comparison analysis, draw conclusion and prepare slides

44. References
6. Conclusion
• Krammes, Raymond A., and Kenneth W. Crowley. "Passenger
car equivalents for trucks on level freeway segments."
Transportation Research Record 1091 (1986).
• Benekohal, Rahim F., and Weixiong Zhao. "Delay-based
passenger car equivalents for trucks at signalized
intersections." Transportation Research Part A: Policy and
Practice 34.6 (2000): 437-457.
• Chandra, Satish, and P. K. Sikdar. "Factors affecting PCU in
mixed traffic situations on urban roads." Road and transport
research 9.3 (2000): 40-50.