POWER TAKE OFF CYCLE DEVELOPMENT 

AND TESTING 

FINAL REPORT 

SwRI® Project No. 03.15777.14 

Prepared for: 

Environmental Protection Agency 

26 West Martin Luther King Drive 

Cincinnati, OH 45268 

Prepared by: 

Joseph W. Anthony, Senior Research Engineer 

Janet Buckingham, Staff Analyst 

Ashok Nedungadi, Principal Engineer 

Joe Steiber, Principal Engineer 

Glen Wendel, Staff Engineer 

September 2010 

 
 

POWER TAKE OFF CYCLE DEVELOPMENT 

AND TESTING 

FINAL REPORT 

SwRI® Project No. 03.15777.14 

Prepared for: 

Environmental Protection Agency 

26 West Martin Luther King Drive 

Cincinnati, OH 45268 

September 2010 

Prepared by: Approved by: 

 

______________________________ _________________________________ 

Joseph W. Anthony Jayant Sarlashkar 

Senior Research Engineer Manager 

Department of Engine and Vehicle R&D Department of Engine and Vehicle R&D 

 

DEPARTMENT OF ENGINE AND VEHICLE R&D 

ENGINE, EMISSIONS AND VEHICLE RESEARCH DIVISION 

This report shall not be reproduced, except in full, without the written approval of Southwest Research Institute®. Results and 

discussion given in this report relate only to the test items described in this report.
FINAL REPORT 03-15777.14 ii 

TABLE OF CONTENTS 

Page

LIST OF FIGURES ...................................................................................................................... iii 

LIST OF TABLES ........................................................................................................................ iv 

1.0 INTRODUCTION ............................................................................................................ 1 

2.0 TASK 1 - INITIAL RESEARCH IN FIELD .................................................................... 2 

3.0 TASK 2 - APPLIED PTO RESEARCH ........................................................................... 3 

4.0 TASK 3 - DUTY CYCLE ANALYSIS ........................................................................... 10 

5.0 TASK 4 - DUTY CYCLE DEVELOPMENT .................................................................. 31 

6.0 TASK 5 - TEST RIG RESEARCH AND DEVELOPMENT ......................................... 35 

7.0 SUMMARY ..................................................................................................................... 38 

..
FINAL REPORT 03-15777.14 iii 

LIST OF FIGURES 

Figure Page

1 Utility Truck Used for In-Use Data Logging .................................................................4 

2 Flow Meter and Pressure Transducer Installed on Utility Truck ...................................4 

3 Example of Data Recorded from Utility Truck ..............................................................5 

4 An Example of an Automated Side Loader (ASL) Refuse Truck ..................................6 

5 PTO Driven Pumps for ASL Refuse Truck ....................................................................7 

6 Flow Meter and Pressure Transducer Installed on Inlet to Loader Valve Body 

for ASL Refuse Truck ....................................................................................................7 

7 Flow Meter and Pressure Transducer Installed on Inlet to Compactor Valve Body 

for ASL Refuse Truck ....................................................................................................8 

8 Example of Loader Data Recorded from ASL Refuse Truck .........................................8 

9 Example of Compactor Data Recorded from ASL Refuse Truck ...................................9 

10 Example of Engine Speed and Vehicle Speed Data Recorded 

from ASL Refuse Truck ..................................................................................................9 

11 Utility Truck Pump Pressure Relative Frequency Histogram for PTO “ON” 

Operation During Rural Testing ...................................................................................12 

12 Utility Truck Pump Pressure Relative Frequency Histogram for PTO “ON” 

Operation During Urban Testing ..................................................................................16 

13 Refuse Truck Compactor Pressure Relative Frequency Histogram for PTO “ON” 

Operation When Only the Compactor was Operating ..................................................21 

14 Refuse Truck Loader Pressure Relative Frequency Histogram for PTO “ON” 

Operation When Only the Loader was Operating ........................................................23 

15 Refuse Truck Compactor Pressure Relative Frequency Histogram for PTO “ON” 

Operation When Both Compactor and Loader Were Operating ..................................26 

16 Refuse Truck Loader Pressure Relative Frequency Histogram for PTO “ON” 

Operation When Both Compactor and Loader Were Operating ..................................26 

17 Cluster Analysis Means for Refuse Truck when Both Loader and Compactor 

Were Operating Using Selected Data ...........................................................................29 

18 FFT Plot for Refuse Truck Compactor Operation ........................................................32 

19 FFT Plot for Refuse Truck Loader Operation ..............................................................32 

20 Hydraulic System Simulator Circuit Schematic ...........................................................35 

..
FINAL REPORT 03-15777.14 iv 

LIST OF TABLES 

Table Page

1 Utility Truck Configuration ...............................................................................................3 

2 Refuse Truck Configuration ..............................................................................................6 

3 Definitions of PTO Operation for the Utility Truck ........................................................10 

4 Time at Various Operating Conditions for Utility Truck Rural Testing .........................11 

5 Pump Pressure Percentiles for Time at PTO “ON” Operation for Utility Truck 

Rural Testing ...................................................................................................................13 

6 Steady-State Modes for Rural Utility Truck Cycle .........................................................13 

7 Time at Various Operating Conditions for Utility Truck Urban Testing ........................15 

8 Pump Pressure Percentiles for Time at PTO “ON” Operation for Utility Truck 

Urban Testing ..................................................................................................................16 

9 Steady-State Modes for Urban Utility Truck Cycle ........................................................17 

10 Definitions of PTO Operation for Refuse Truck .............................................................18 

11 Time at Various Operating Conditions for Refuse Truck Testing ..................................19 

12 Compactor Pressure Percentiles for Time When Only The Compactor was in 

Operation for Refuse Truck Testing ................................................................................22 

13 Cluster Analysis Results for Compactor Only PTO “ON” Operation for Refuse 

Truck ...............................................................................................................................22 

14 Loader Pressure Percentiles for Time When Only Loader was in Operation for 

Refuse Truck Testing ......................................................................................................24 

15 Cluster Analysis Results for Loader Only PTO “ON” Operation for Refuse Truck ......25 

16 Compactor and Loader Pressure Percentiles for Time When Both were in 

Operation for Refuse Truck Testing ................................................................................27 

17 Percent of Total Time at Compactor and Loader Pressure When Both are 

Operating for the Refuse Truck .......................................................................................27 

18 Cluster Analysis Results for Both Compactor and Loader PTO “ON” 

Operation for Refuse Truck Using Selected Data ...........................................................29 

19 Final Steady-State Modes for Both Compactor and Loader PTO “ON” 

Operations for the Refuse Truck Using all Data .............................................................30 

20 Composite 10-Minute Cycle Times by Vehicle and Application ...................................31 

21 Composite 10-Minute Cycle Times for Each Mode .......................................................33 

22 Final Composite 10-Minute PTO Duty Cycle .................................................................34 
FINAL REPORT 03-15777.14 1 of 38 

1.0 INTRODUCTION 

In an effort to evaluate and address the impacts of Power-Take-Off (PTO) for engine 

performance, the Environmental Protection Agency (EPA) requested Southwest Research 

Institute (SwRI) to evaluate engine and vehicle performance of utility vehicles and refuse haulers 

for boom operation; particularly where power demands are associated with use of these 

implements. It is essential to be able to characterize the needs of the conventional as well as the 

alternative hybrid designs on a consistent basis. To that end, background research was conducted 

to determine which vehicles were most likely to be fitted with hybrid PTO systems. Data were 

collected to determine the operating regime to develop the appropriate duty cycle to assess PTO 

operation overall. A test rig was designed for properly exercising these vehicle components. 

 
FINAL REPORT 03-15777.14 2 of 38 

2.0 TASK 1 - INITIAL RESEARCH IN FIELD 

A literature review of on-highway truck applications utilizing power take-off (PTO) (by 

vehicle class and use) was conducted in order to characterize the operations that require the use 

of PTO. The literature search focused on the following topics. 

o Existence of available duty cycles representative of PTO operation 

o Engine parameters including speed, torque, and fuel consumption during PTO 

operations 

o PTO hydraulic pressure and flow 

o Estimates of annual sales volumes for each type of application of PTO equipment 

o Available test rigs 

Potential for the adoption of hybrid power systems in these applications and their effects during 

PTO operation, including reductions in energy consumption and GHG emissions were also 

considered. 

The literature search spanned technical contributions from the past ten years and focused 

on PTO duty cycles for both conventional and hybrid powertrains. Although, hybrid PTO 

systems have been implemented on utility truck for many years, a search of the most recent SAE 

and pertinent technical papers on the subject of PTO operations for a variety of on-road vehicle 

classes resulted in the following two papers, 

H. C.Frey, K. Kim, Comparison of Real-World Fuel Use and Emissions for Dump 

Trucks Fueled with B20 Biodiesel Versus Petroleum Diesel, 85th Annual Meeting of the 

Transportation Research Board, 2006 

SwRI, 2007. Southwest Research Institute. Emissions and Fuel Economy Testing of 

Three Utility Trucks. SwRI Project No. 03.11602. March 9, 2007. 

The search included annual sales volumes for as many PTO-equipped vehicle groups as 

the schedule allowed with concentration on vehicles with large volume sales in 2011 and 

beyond. However, these data are not, generally, made public by any of the manufacturers or 

trade associations. During the literature search, industry contacts were consulted to determine 

which vehicles were most likely to be hybridized in large volumes. Two major applications were 

cited as being candidates, utility boom trucks (utility) and automated side loader (ASL) refuse 

trucks. It is generally accepted that there are approximately 150,000 utility boom trucks in 

operation in the United States and approximately 100,000 refuse trucks in operation, of which 

20,000 are ASL-type refuse trucks. Based on recommendations from manufacturers and 

engineering judgment, it was decided to instrument utility boom trucks and ASL refuse trucks. 

The utility trucks were chosen due to their propensity for hybridization and their large fleet size. 

ASL refuse trucks were chosen despite their current, relatively small population because it is 

projected that they will become increasingly common as municipalities continue to switch to 

automated pick-up to reduce labor costs. Manufacturers also indicated that there are plans to 

develop hybrid PTO systems for ASL trucks in the near future. 
FINAL REPORT 03-15777.14 3 of 38 

3.0 TASK 2 - APPLIED PTO RESEARCH 

The objective of this task was to quantify PTO work during PTO operations and the 

percentage of time that PTO operations take place in a one-day time frame for the various classes 

of vehicles considered in Task 1. The data collected was used to develop a composite PTO duty 

cycle that can serve to compare the fuel efficiency of one vehicle over the other as well as define 

the design parameters for the construction of a PTO test rig. 

 From Task 1, it was determined that utility aerial boom trucks and refuse trucks were the 

most likely applications for hybrid PTO systems due to their PTO duty cycle. It was originally 

planned to combine in-use field data logging with existing data from PTO and truck 

manufacturers, but no existing data were made available for this project. 

SwRI obtained one utility boom truck and one refuse truck to instrument for data 

collection while in-use. The utility truck was a 2008 Ford F-750, Figure 1, was equipped with a 

Caterpillar C7 diesel engine, an automatic Allison five-speed transmission, and Eaton PTO and 

pump. The specifications of this truck are listed in Table 1. A turbine-style flow meter and a 

pressure transducer were installed on the outlet side of the hydraulic pump to allow the pump 

flow and pressure, shown in Figure 2. The truck’s J1939 CAN communication was used to 

record vehicle speed, engine speed, engine fuel rate, and engine load. An example of the data 

recorded is shown in Figure 3. Together, these data were used to determine the amount of time 

the PTO was used compared to the amount of time the vehicle was in operation. The utility 

truck was operated for a total of four weeks, two weeks each in two different geographic 

locations, urban and rural, for this project. 

TABLE 1. UTILITY TRUCK CONFIGURATION 

Vehicle 

2008 Ford F-750 

VIN 3FRXF75T99V100971 

Engine Caterpillar C7 

Emission controls EGR, DPF 

Rated power, hp 250 

Transmission Allison Automatic, 5-speed 

GVWR, lb 33,000 

PTO Pump Eaton, 14 gpm@700 RPM 
FINAL REPORT 03-15777.14 4 of 38 

FIGURE 1. UTILITY TRUCK USED FOR IN-USE DATA LOGGING 

FIGURE 2. FLOW METER AND PRESSURE TRANSDUCER 

INSTALLED ON UTILITY TRUCK 
FINAL REPORT 03-15777.14 5 of 38 

FIGURE 3. EXAMPLE OF DATA RECORDED FROM UTILITY TRUCK

It was decided to instrument an Automated Side Loader (ASL) refuse truck for this 

project since they are becoming more popular and have a higher PTO load than traditional rear 

load refuse trucks. Due to proprietary concerns, a photograph of the actual test truck is not in 

this report. Figure 4 shows a generic ASL refuse truck. The truck instrumented for this project 

was a 2010 Mack equipped with a Mack 10L diesel engine and an Allison automatic 5-speed 

transmission. The specifications for this truck are shown in Table 2. The ASL truck has two 

hydraulic pumps for each of the two hydraulic circuits, Figure 5. One circuit is for the side 

loader arm and the other is for compaction. Traditional rear load refuse trucks only have a 

compaction circuit. Each hydraulic circuit was instrumented with a turbine-style flow meter and 

pressure transducer, however, due to packaging constraints, the flow meter and pressure 

transducer for each circuit was mounted at the inlet of the valve body controlling the flow to 

each circuit’s actuators. Although it may have been preferable to measure the pressure at the 

pump’s outlet, it was assumed that the pressure drop in the lines was negligible. Figure 6 shows 

the flow meter and pressure transducer for the loader arm and Figure 7 shows the flow meter and 

pressure transducer for the compactor. As with the utility truck, the ASL truck’s J1939 CAN 

communication was used to record vehicle speed, engine speed, engine fuel rate, and engine 

load. 

0

500

1000

1500

2000

2500

3000

0

10

20

30

40

50

60

70

80

5000 5500 6000 6500 7000 7500

Pressure,psi

& Engine Speed, rpm

Flow, gal/min

& Vehicle Speed, kph

Time,seconds

Pump flow

Vehicle speed

Pump pressure

Engine speed
FINAL REPORT 03-15777.14 6 of 38 

FIGURE 4. AN EXAMPLE OF AN AUTOMATED SIDE LOADER (ASL) 

REFUSE TRUCK 

TABLE 2. ASL REFUSE TRUCK CONFIGURATION 

Vehicle 

2010 Mack 

VIN 1M2AU02C6AM004642 

Engine Mack MP7-405M 

Emission controls EGR, DPF 

Rated power, hp 405 

Transmission Allison 4500 RDS 

GVWR, lb 56,000 

PTO Pump Arm: Parker, 16 gpm@700 RPM 

Compactor: Parker, 23 gpm@700 RPM 
FINAL REPORT 03-15777.14 7 of 38 

FIGURE 5. PTO DRIVEN PUMPS FOR ASL REFUSE TRUCK 

FIGURE 6. FLOW METER AND PRESSURE TRANSDUCER INSTALLED ON 

INLET TO LOADER VALVE BODY FOR ASL REFUSE TRUCK 
FINAL REPORT 03-15777.14 8 of 38 

FIGURE 7. FLOW METER AND PRESSURE TRANSDUCER INSTALLED 

ON INLET TO COMPACTOR VALVE BODY 

 FOR ASL REFUSE TRUCK 

The added signals reduced the data sampling rate from 1 Hz to 0.5 Hz. The reduced 

sampling rate was acceptable for this work. The ASL truck was instrumented for two weeks of 

calendar time, however, due to a failed pressure transducer, accidental damage, and two 

connector failures, there were only five days of usable data. Figures 8 through 10 are examples 

of data recorded from the ASL truck. 

FIGURE 8. EXAMPLE OF LOADER DATA RECORDED FROM 

ASL REFUSE TRUCK 

0

5

10

15

20

10350 10370 10390 10410 10430 10450 10470 10490

Time, seconds

Flow, gal/min

0

500

1000

1500

2000

2500

Pressure, psi 

Loader flow

Loader pressure
FINAL REPORT 03-15777.14 9 of 38 

FIGURE 9. EXAMPLE OF COMPACTOR DATA RECORDED FROM 

ASL REFUSE TRUCK 

FIGURE 10. EXAMPLE OF ENGINE SPEED AND VEHICLE SPEED DATA 

RECORDED FROM ASL REFUSE TRUCK 

0

5

10

15

20

25

30

35

40

45

50

10350 10370 10390 10410 10430 10450 10470 10490

Time, seconds

Flow, gal/min 

0

500

1000

1500

2000

2500

Pressure, psi 

Compactor flow

Compactor pressure

0

5

10

15

20

25

30

10350 10370 10390 10410 10430 10450 10470 10490

Time, seconds

 Vehicle Speed, kmh

0

200

400

600

800

1000

1200

1400

1600

1800

2000

 Engine Speed, rpm

Vehicle speed

Engine speed
FINAL REPORT 03-15777.14 10 of 38 

4.0 TASK 3 - DUTY CYCLE ANALYSIS 

Data collected for the Task 2 database were used to determine individual representative 

duty cycles for PTO work for the utility boom truck and the ASL refuse truck. Only data 

pertinent to the operation of the PTO were used in the duty cycles. Analyses of the data 

collected for the utility truck and the refuse truck are described in the sections below. 

4.1 Utility Boom Truck Duty Cycle 

Data collected during Task 2 for the utility truck cycle development consisted of 

hydraulic pump pressure (psi) and pump flow (gal/min) versus time (seconds). Utility truck 

operations were performed in a rural environment (San Antonio) and in an urban environment 

(Fort Worth). Data from both of these environments were combined to produce one individual 

utility truck cycle. For the purposes of the cycle development, data were selected only during the 

component operation when the truck was not moving (i.e, vehicle speed = 0). In addition, pump 

flow and pump pressure conditions were also analyzed in order to identify idle and PTO 

operations. Table 3 lists the definitions of the various PTO operations. If a single data recording 

resulted in the pump pressure ≥ 200 and the pump flow > 0, then the PTO was considered to be 

operating (i.e, “on”). PTO was considered “off’ if the pump pressure < 200 and the pump flow = 

0. Data were not included in the duty cycle analyses for the PTO “off” condition. Lower 

pressures were considered to be within the ‘noise’ of the instrumentation and do not reflect PTO 

operation even though they were recorded as non-zero. The noise was defined as any pressure 

value below the maximum reading with the PTO “off.” Two different situations represent idle 

periods. Idle 1 was defined when pump pressure was high but the pump was not flowing. Idle 2 

was defined when there was low pump pressure (i.e., within the ‘noise’) but there was some 

pump flow. Note that almost all of the idle data collected on the utility truck in the rural setting 

met the criteria for Idle 1 (no pump flow). 

TABLE 3. DEFINITIONS OF PTO OPERATION 

FOR THE UTILITY TRUCK 

Pump 

Pressure, psi 

Pump Flow, gal/min 

0 > 0 

< 200 PTO Off Idle 2 

≥ 200 Idle 1 PTO On 

 All the data collected for the utility truck operation in the rural setting were combined 

into one database wherein each second-by-second recording was identified by one of the four 

operating conditions outlined in Table 3. The data were then divided into ten separate key-on 

“events” which were defined by a gap in the consecutive time stamp during the data recording. 

This was done to examine continuous PTO operations. Table 4 summarizes the available utility 

truck data collected in the rural environment. Approximately 85% of the total data collected 

represented time when the vehicle speed = 0. For purposes of the cycle development, 9.66% of 

the time was spent in PTO “on” operation while 90.34% of the time was spent in the idle 

conditions. 
FINAL REPORT 03-15777.14 11 of 38 

TABLE 4. TIME AT VARIOUS OPERATING CONDITIONS FOR 

UTILITY TRUCK RURAL TESTING 

Events 

Total Test 

Time, sec 

Vehicle Speed = 0 

PTO On Idle 1 Idle 2 PTO Off 

Time (sec) at 

Pump Flow > 0 

and Pump 

Pressure ≥ 200 

Time (sec) at 

Pump Flow = 

0 and Pump 

Pressure ≥

200 

Time (sec) at 

Pump Flow > 

0 and Pump 

Pressure < 

200 

Time (sec) at 

Pump Flow = 

0 and Pump 

Pressure < 

200 

1 197 35 124 0 38 

2 1433 2 15 0 145 

3 911 0 0 0 105 

4 49191 8554 31090 685 1056 

5 5786 248 2412 0 127 

6 8000 1451 6082 0 69 

7 22250 47 21151 0 29 

8 29985 2340 21361 0 193 

9 32507 68 28990 3 964 

10 9578 8 7312 0 435 

TOTAL 159838 12753 118537 688 3161 

% Time at PTO On and Idle 9.66% 90.34% 

 

Basic descriptive statistics and histograms of the collected pump pressure data over time 

were used to quantify the percentage of time various pressure levels were maintained. 

Scatterplots of pump pressure vs. time were also generated in order to determine whether the 

duty cycle warranted a steady-state or transient characterization. 

Figure 11 illustrates a relative frequency histogram of the pump pressure during the PTO 

‘on’ operation for the utility truck tested in the rural environment. Note that the pressure data are 

concentrated around 2400-2500 psi with a very small percentage of the pressures < 1000 psi. 

Table 5 lists the cumulative percentiles of the pump pressure data for the rural utility 

truck testing. Approximately 90% of the pump pressures lie between 2026.3 and 2575.6 psi 

(difference = 548.7 psi) while 80% of the pump pressures lie between 2324.7 and 2558.8 psi 

(difference = 234.1 psi). Since the range of pump pressure for the PTO ‘on’ operation is within 

the expected variation of pressure at a constant PTO operation for the utility truck, a single 

steady-state PTO ‘on’ mode was investigated to represent the utility truck operation in the rural 

environment. 

 
FINAL REPORT 03-15777.14 12 of 38 

Scatterplots of the pump pressure vs. time data also indicated that the selection of a single 

operational mode was suitable since the PTO ‘on’ conditions could be easily identified when the 

pump pressure was sustained and targeted near 2500 psi. Thus, the rural utility truck operation 

was defined using two steady-state modes (PTO ‘on’ and idle) as defined in Table 6. The pump 

pressure representing the PTO ‘on’ condition was set to the average pump pressure during that 

operation. The statistical frequency analysis of the in-field data was used to determine the 

relative proportion of time allocated to each steady-state mode. Finally, the average pump 

pressure was normalized as a percentage of the maximum operating pump pressure rating for the 

pump used in the utility truck (3000 psi). The nominal operating pressure for the hydraulic 

pump is 2500 psi, but pressure varied depending on the load and spiked to higher values when 

the flow was interrupted abruptly. Thus, the PTO ‘on’ steady-state mode would be run at 

80.45% of the rated maximum pump pressure. 

 

FIGURE 11. UTILITY TRUCK PUMP PRESSURE RELATIVE FREQUENCY 

HISTOGRAM FOR PTO “ON” OPERATION DURING RURAL TESTING 
FINAL REPORT 03-15777.14 13 of 38 

TABLE 5. PUMP PRESSURE PERCENTILES FOR TIME AT PTO 

 “ON” OPERATION FOR UTILITY TRUCK RURAL TESTING 

Percentile, % 

Pump 

Pressure, psi 

100 (max) 2920.90 

95 2575.60 

90 2558.80 

80 2536.90 

70 2519.30 

60 2503.20 

50 2486.40 

40 2466.60 

30 2443.20 

20 2411.00 

10 2324.70 

5 2026.30 

0 (min) 200.43 

TABLE 6. STEADY-STATE MODES FOR RURAL UTILITY TRUCK CYCLE 

Mode 

% Time at 

Mode 

Avg. Pump 

Pressure, psi 

Max Pump 

Pressure 

Rating, psi 

Normalized 

Avg. Pump 

Pressure, % 

1 9.66 2413.53 3000 80.45 

2 (Idle) 90.34 0 3000 0 

The second set of data collected for the utility truck operation occurred in the urban 

setting in Fort Worth. Again, all the data were combined into one database wherein each secondby-second recording was identified by one of the four operating conditions outlined in Table 3. 

Between the rural and urban data collection the flowmeter was replaced. This change resulted in 

a slight flow offset at zero flow. Therefore, it was decided that a pump flow ≥ 1 gal/min would 

be used to as part of the PTO ‘on’ condition. The pump flow definition for the operating 

conditions was changed from 0 to 1 gal/min to reflect the lower volume flowmeter in the truck 

operating in the urban setting. The data were then divided into 46 separate key-on “events” 

which were defined by a gap in the consecutive time stamp during the data recording. 

Table 7 summarizes the available utility truck data collected in the urban environment. 

Approximately 69% of the total data collected represented time when the vehicle speed = 0. For 

purposes of the cycle development, 49.89% of the time was spent in PTO “on” operation while 

50.11% of the time was spent in the idle and PTO ‘off’ conditions. This is drastically different 
FINAL REPORT 03-15777.14 14 of 38 

than the percentage of time calculated for the PTO ‘on’ condition during the rural testing period. 

The PTO ‘off’ data were included in this urban setting analysis because the operator in the urban 

environment performed more operations per day than the rural operator. In rural operation, the 

operator allowed the PTO to be engaged for long periods of time, sometimes several hours, 

producing high pressure and no flow and it was decided that this was unnecessary load that 

should not be considered for the cycle development. In urban operation, there were high 

pressure events with no flow, but those events typically occurred intermittently during normal 

operation. 

Similar analyses used in the investigation of the rural utility truck data were again 

performed using the urban utility truck data. Basic descriptive statistics and histograms of the 

collected pump pressure data over time were used to quantify the percentage of time various 

pressure levels were maintained. Similarly, scatterplots of pump pressure vs. time were also 

generated in order to determine whether the duty cycle warranted a steady-state or transient 

characterization. Figure 12 illustrates a relative frequency histogram of the pump pressure 

during the PTO ‘on’ operation for the utility truck tested in the urban environment. Note that the 

pressure data are concentrated around 2500 psi with a very small percentage of the pressures < 

2000 psi. These pressure data demonstrated smaller variation than those collected in the rural 

setting. Table 8 lists the cumulative percentiles of the pump pressure data for the urban utility 

truck testing. Approximately 90% of the pump pressures lie between 2351.79 and 2578.56 psi 

(difference = 226.77 psi) while 80% of the pump pressures lie between 2432.26 and 2566.85 psi 

(difference = 134.59 psi). Analogous to the conclusions made for the urban truck usage data, the 

range of pump pressure for the PTO ‘on’ operation is within the expected variation of pressure at 

a constant PTO operation for the utility truck; therefore, a single steady-state PTO ‘on’ mode 

was used to represent the utility truck operation in the urban environment. This was confirmed 

in the scatterplots of the pump pressure vs. time data which also indicated that the selection of a 

single operational mode was suitable since the PTO ‘on’ conditions could be easily identified 

when the pump pressure was sustained and targeted near 2500 psi. Thus, the urban utility truck 

operation was defined using two steady-state modes (PTO ‘on’ and idle+PTO ‘off’) as defined in 

Table 9. The pump pressure representing the PTO ‘on’ condition was set to the average pump 

pressure during that operation. The statistical frequency analysis of the in-field data was used to 

determine the relative proportion of time allocated to each steady-state mode. Finally, the 

average pump pressure was normalized as a percentage of the maximum operating pump 

pressure rating for the pump used in the utility truck (3000 psi). Thus, the PTO ‘on’ steady-state 

mode would be run at 83.47% of the rated maximum pump pressure, which is very close to the 

normalized pressure computed for the PTO ‘on’ steady-state mode in the rural setting. 

 
FINAL REPORT 03-15777.14 15 of 38 

TABLE 7. TIME AT VARIOUS OPERATING CONDITIONS 

FOR UTILITY TRUCK URBAN TESTING 

Events 

Total Test 

Time, sec 

Vehicle Speed = 0 

PTO On Idle 1 Idle 2 PTO Off 

Time (sec) at Pump 

Flow ≥ 1 and Pump 

Pressure ≥ 200 

Time (sec) at Pump 

Flow < 1 and Pump 

Pressure ≥ 200 

Time (sec) at Pump 

Flow ≥ 1 and Pump 

Pressure < 200 

Time (sec) at Pump 

Flow < 1 and Pump 

Pressure < 200 

1 37 13 3 0 21 

2 868 0 0 0 90 

3 1939 0 0 0 575 

4 135 0 0 0 25 

5 2091 0 0 0 23 

6 348 0 0 0 348 

7 3706 0 0 0 585 

8 99 0 0 0 50 

9 3531 0 0 0 235 

10 3279 0 0 0 8 

11 997 0 0 0 70 

12 5700 0 0 0 111 

13 98 0 0 0 51 

14 105 0 0 0 38 

15 60 0 0 0 31 

16 1369 0 0 0 42 

17 1039 0 0 0 107 

18 39 0 0 0 6 

19 590 0 0 0 69 

20 1497 0 0 0 247 

21 54 0 0 0 6 

22 20 6 1 0 12 

23 35 0 13 0 22 

24 324 321 1 0 1 

25 43 40 2 0 1 

26 180 177 3 0 0 

27 207 126 23 0 3 

28 1722 1371 15 0 210 

29 218 0 0 0 154 

30 1837 78 28 40 1691 

31 296 0 0 4 229 

32 89 0 0 0 27 

33 2605 0 0 3 1127 

34 527 0 0 0 121 

35 22941 13485 72 3 3707 

36 455 206 31 3 215 

37 5920 0 0 0 3014 

38 30812 19820 129 4 5482 

39 34188 17587 96 104 10351 

40 5161 2757 37 5 491 

41 36693 9913 89 4 17955 

42 23146 5037 70 1 11367 

43 16515 6322 19 3 5895 

44 5925 1388 32 0 3001 

45 30509 10767 34 3 10035 

46 11776 343 31 3 11399 

TOTAL 259725 89757 729 180 89248 

% Time at PTO On 

and Idle 49.89% 50.11% 
FINAL REPORT 03-15777.14 16 of 38 

FIGURE 12. UTILITY TRUCK PUMP PRESSURE RELATIVE FREQUENCY 

HISTOGRAM FOR PTO “ON” OPERATION DURING URBAN TESTING 

TABLE 8. PUMP PRESSURE PERCENTILES FOR TIME AT PTO 

“ON” OPERATION FOR UTILITY TRUCK URBAN TESTING 

Percentile, 

% 

Pump 

Pressure, psi 

100 (max) 2963.33 

95 2578.56 

90 2566.85 

80 2555.88 

70 2548.56 

60 2541.98 

50 2534.67 

40 2526.62 

30 2514.92 

20 2486.39 

10 2432.26 

5 2351.79 

0 (min) 236.28 
FINAL REPORT 03-15777.14 17 of 38 

TABLE 9. STEADY-STATE MODES FOR 

URBAN UTILITY TRUCK CYCLE 

Mode 

% Time at 

Mode 

Avg. Pump 

Pressure, psi 

Max Pump 

Pressure 

Rating, psi 

Normalized 

Avg. Pump 

Pressure, % 

1 49.89 2504.14 3000 83.47 

2 (Idle) 50.11 0 3000 0 

4.2 Refuse Truck Duty Cycle 

Data collected during Task 2 for the refuse truck cycle development consisted of 

hydraulic pump pressure (psi) and pump flow (gal/min) versus time (seconds). All the refuse 

truck operations were performed in a residential environment in Conroe, TX. For the purposes 

of the cycle development, data collected during the driving times of the refuse truck in 

association with the refuse dump facility and driving times between residential areas were 

excluded from the analyses. The PTO is always in operation on this type of vehicle as the PTO 

pumps are coupled to the engine’s crankshaft. In discussion with EPA personnel it was decided 

to distinguish between driving and PTO operation. Therefore, data collected when truck is 

driving to and from fleet garage and to and from the landfill was excluded from the idle time of 

the PTO operation. Recall from Task 2 that the refuse truck recorded pressure and flow for two 

separate hydraulic loops instead of a single loop as was the case with the utility truck. One loop 

operated a side loader and the other loop operated the compactor. Thus, it was possible to 

examine the data under four different PTO operating conditions: (1) both the compactor and 

loader worked simultaneously, (2) compactor only, (3) loader only, and (4) both compactor and 

loader at idle. 

Pump flow and pump pressure conditions were analyzed in order to identify idle and the 

PTO ‘on’ operations. During the data analysis, it was discovered that the loader and compactor 

pressures appeared lower than expected. It was found that the calibration gains were not updated 

in the acquisition program for the transducers installed on the refuse truck. The original data 

acquisition program was calibrated for transducers operating from 0-5VDC instead of 1-5VDC, 

for the same pressure range of 0 to 3000 psi. This resulted in the compactor and loader pressures 

being recorded with the wrong transfer function. The issue was resolved by re-scaling these 

pressure data by 1.25 during post-processing. 

Table 10 lists the definitions of idle and PTO ‘on’ for the refuse truck. These flow and 

pressure definitions applied for both the compactor and loader. If a single data recording 

resulted in the pump pressure ≥ 150 and the pump flow ≥ 2, then the PTO was considered to be 

operating (i.e, “on”). These thresholds were slightly above the typical values of the transducers 

when each pump was known to be off. Alternatively, PTO was considered in idle mode if these 

criteria were not met. Three different situations represent idle periods. Idle 1 was defined when 

pump pressure was high but the pump flow was very low. Idle 2 was defined when there was 

low pump pressure (i.e., within the ‘noise’) but pump flow was above the noise. Lastly, Idle 3 

was defined as both very low pressure and flow. For the duty cycle development analyses, all 

three idle conditions were combined as one idle definition. 
FINAL REPORT 03-15777.14 18 of 38 

TABLE 10. DEFINITIONS OF PTO OPERATION FOR REFUSE TRUCK 

Pump 

Pressure, 

psi 

Pump Flow, gal/min 

< 2 ≥ 2 

< 150 Idle 3 Idle 2 

≥ 150 Idle 1 PTO On 

All the data collected for the refuse truck operation were combined into one database. 

Unlike the data collected during the utility truck phase, the refuse truck recorded data in 0.5 Hz 

or every 2 seconds instead of every 1 second. Thus, each data observation represents a twosecond interval. However, frequency counts and percentage of total time calculations are not 

influenced by the amount of time each recorded observation represents. For that reason all the 

tables represented in this section are the actual number of data observations and not the actual 

time elapsed during the data collection. Each two-second recording was identified by either the 

idle condition or the PTO ‘on’ operating condition outlined in Table 10. Also different from the 

utility truck data, the refuse data were not divided into separate key-on “events” because the 

operation of the truck was continuous once it arrived at a residential area. 

Table 11 summarizes the refuse truck data collected by the various operating conditions. 

For purposes of the refuse truck cycle development, 22.01% of the time was spent in the loader 

only PTO ‘on’ operation, 25.96% of the time was spent in the compactor only PTO ‘on’ 

operation, and 20.07% of the time was spent when both the compactor and the loader were 

operating in the PTO ‘on’ condition. Idle conditions comprised 31.96% of the total available 

time. 

Since the refuse truck data consisted of pressures from two independent loops (compactor 

and loader), the analysis to generate representative duty cycles was more complicated. Each of 

the three PTO ‘on’ operations was analyzed separately to obtain duty cycles and then they were 

combined to represent the refuse truck cycle. It was decided that a multi-mode steady-state duty 

cycle for each PTO ‘on’ operation would be explored and that a systematic repetition of these 

modes could simulate the cyclic operation of the refuse truck, especially with the loader 

operation. 
FINAL REPORT 03-15777.14 19 of 38 

TABLE 11. TIME AT VARIOUS OPERATING CONDITIONS 

FOR REFUSE TRUCK TESTING 

Day 

Total 

Available 

PTO Test 

Time, sec 

PTO 

Operation 

Both 

Compactor 

and Loader: 

Time (sec) at 

Pump Flow ≥

2 and Pump 

Pressure ≥

150 

PTO 

Operation 

Compactor 

Only: 

Time (sec) at 

Pump Flow ≥

2 and Pump 

Pressure ≥

150 

PTO 

Operation 

Loader Only: 

Time (sec) at 

Pump Flow ≥

2 and Pump 

Pressure ≥

150 

Idle for 

Both 

Compactor 

and Loader 

1 12525 3089 2958 3137 3341 

2a 37000 0 0 0 0 

3 24145 4425 6241 5400 8079 

4 38915 7775 10227 8163 12750 

5 7468 1377 2135 1583 2373 

Total Time 83053 16666 21561 18283 26543 

Actual 

Time, hr 46.14 9.26 11.98 10.16 14.75 

% of Total 

Time 20.07% 25.96% 22.01% 31.96% 

a All data from Day 2 were excluded from the analyses due to wiring harness being damaged 

 during truck maintenance. 

The compactor only and loader only operations when the PTO was ‘on’ were 

independently analyzed using a statistical cluster analysis to help place the pressure observations 

into groups, or clusters, suggested by the data. Pressures in a given cluster would tend to be 

similar to each other; thus, defining possible pressure modes. There are several varieties of 

clustering methods and the one chosen for this analysis was oriented toward finding disjoint 

clusters, i.e., clusters where the pressure values are placed in one and only one cluster. The 

disjoint cluster analysis was based on Euclidean distance computed from one or more 

quantitative variables. For the compactor only and loader only PTO “on’ operations, the only 

cluster variable was the pump pressure. However, for the situation where both the compactor 

and loader were operating simultaneously, both the compactor pump pressure and the loader 

pump pressure were used as the two clustering variables. 

The FASTCLUS® procedure in the SAS® software was used to perform all of the cluster 

analyses. This procedure divides the observations into clusters; i.e., groups of data such that all 

Euclidean distances between observations in the same cluster are less than all Euclidean 

distances between observations in different clusters. The Euclidean distances are computed 

using one or more quantitative variables. For example, when both the compactor and loader of 

the tested refuse truck were operating simultaneously, both the compactor pump pressure and the 
FINAL REPORT 03-15777.14 20 of 38 

loader pump pressure were used as the two clustering variables. This kind of clustering is based 

on a k-means model, and it uses a method called nearest centroid sorting. 

A typical cluster analysis consisted of the following steps. 

1. A first pass was made with FASTCLUS to find a set of points to use as the initial cluster 

seeds (i.e., a first guess of the means of the clusters). 

2. Several independent FASTCLUS runs were then made using 2, 3, 4, 5, 6, or 7 clusters 

with the saved seeds from Step 1. 

3. For each run in Step 2, each observation was assigned to the nearest seed to form 

temporary clusters. The seeds were then replaced by the means of the temporary clusters, 

and the process was repeated until no further changes occurred in the clusters. 

4. For each computer run made in Step 2, the cubic clustering criterion (CCC) was 

computed. This criterion was used to determine how many clusters were appropriate. 

When the CCC reached its maximum among these runs, the corresponding number of 

clusters being used provided a good estimate of the number of population clusters. For 

example, in the case described above for the refuse truck data with the two clustering 

variables, the chosen number of clusters based on the CCC criterion was 4. 

5. With the optimal number of clusters from Step 5, the FASTCLUS procedure was re-run 

specifying full replacement of the default seed used to form clusters. For our refuse truck 

example, there were 4 clusters. The output provided the number of observations in each 

of the 4 clusters and this was used to compute the proportion (weighting) for the duty 

cycle. 

Histograms of the collected pump pressure data were individually examined for the 

compactor only and loader only data to assist in defining the possible number of clusters. 

Figure_13 illustrates a relative frequency histogram of the pump pressure during the compactor 

only PTO ‘on’ operation for the refuse truck. Note that the pressure data are skewed with the 

majority of the data concentrated around 250-280 psi with a small percentage of the 

pressures__> 1000 psi. This possibly reflects the gradual increase in compactor pressure 

throughout the day as the amount of garbage deposited in the truck increases causes the 

compactor to work harder to compress the contents. This characteristic is represented by Mode 4 

of the compactor cycle. 

Table 12 lists the cumulative percentiles of the compactor pump pressure data for the 

refuse truck testing. Approximately 70% of the pump pressures lie below 374.58 psi while the 

95th percentile compactor pump pressure was at 765.38 psi. 
FINAL REPORT 03-15777.14 21 of 38 

FIGURE 13. REFUSE TRUCK COMPACTOR PRESSURE RELATIVE FREQUENCY 

HISTOGRAM FOR PTO “ON” OPERATION WHEN ONLY THE 

COMPACTOR WAS OPERATING 
FINAL REPORT 03-15777.14 22 of 38 

TABLE 12. COMPACTOR PRESSURE PERCENTILES FOR TIME 

WHEN ONLY THE COMPACTOR WAS IN OPERATION 

FOR REFUSE TRUCK TESTING 

Percentile, % Pressure, psi 

100 (max) 2624.63 

95 765.38 

90 633.89 

80 471.13 

70 374.58 

60 328.60 

50 295.50 

40 265.15 

30 234.81 

20 202.63 

10 173.20 

5 161.25 

0 (min) 150.21 

A cluster analysis was performed on the compactor pressures with up to 5 possible 

clusters. The best analysis resulted in two clusters as defined in Table 13. Cluster #1 reflects the 

area identified in the histogram where the majority of the pressures are concentrated while 

cluster #2 represents the pressures in the long tail of the distribution. These two clusters were 

defined as the two steady-state modes for the compactor-only PTO ‘on’ operation. The 

frequency counts of the two clusters were used to determine the relative proportion of time 

allocated to each steady-state mode. Finally, the average pump pressure in each cluster was 

normalized as a percentage of the maximum operating pump pressure rating for the pump used in 

the refuse truck (2500 psi). Thus, the compactor-only PTO ‘on’ steady-state modes would be 

run at 11.24% of the rated maximum pump pressure for the compactor for Mode 1 and 29.28% 

for Mode 2. 

TABLE 13. CLUSTER ANALYSIS RESULTS FOR COMPACTOR ONLY PTO “ON” 

OPERATION FOR REFUSE TRUCK 

Cluster 

(Mode) 

Total 

Available 

PTO Test 

Time, sec 

% Time 

at Mode 

Avg 

Compactor 

Pressure, psi

Min 

Compactor 

Pressure, psi

Max 

Compactor 

Pressure, psi 

Normalized 

Avg. Pump 

Pressure, 

% 

1 17985 83.41 280.88 150.21 518.03 11.24 

2 3576 16.59 732.03 518.94 2624.6 29.28 

 
FINAL REPORT 03-15777.14 23 of 38 

Histograms of the collected pump pressure data were then examined for the loader only 

data to assist in defining the possible number of clusters. Figure 14 illustrates a relative 

frequency histogram of the pump pressure during the loader only PTO ‘on’ operation for the 

refuse truck. Note that distribution of the pressure data for this operation is very different than 

the one observed in the compactor only data. This distribution appears multi-modal reflecting 

the pressure changes during operation of picking up a container of garbage, dumping it in the 

truck and replacing the container on the group. 

Table 14 lists the cumulative percentiles of the loader pump pressure data for the refuse 

truck testing. Approximately 5% of the pump pressures are below 392.50 psi, 80% of the 

pressures lie below 1421.25 psi while the 95th percentile loader pump pressure was at 1845.00 

psi. 

FIGURE 14. REFUSE TRUCK LOADER PRESSURE RELATIVE FREQUENCY 

HISTOGRAM FOR PTO “ON” OPERATION WHEN ONLY 

THE LOADER WAS OPERATING 
FINAL REPORT 03-15777.14 24 of 38 

TABLE 14. LOADER PRESSURE PERCENTILES FOR TIME 

WHEN ONLY LOADER WAS IN OPERATION FOR 

REFUSE TRUCK TESTING 

Percentile, % Pressure, psi 

100 (max) 2130.00

95 1845.00

90 1782.50

80 1421.25

70 1359.63

60 1295.25

50 1204.26

40 1113.25

30 1031.43

20 926.63

10 714.26

5 392.50

0 (min) 150.71

A cluster analysis was performed on the loader pressures with up to 5 possible clusters. 

The best analysis resulted in four clusters as defined in Table 15. Cluster #1 reflects the area 

identified in the histogram where the pressures are the lowest and starting to increase in 

frequency after 500 psi. Cluster #2 represents the pressures increasing up through approximately 

1150 psi while Cluster #3 includes the highest number of data points at slightly higher pressures. 

Lastly, Cluster #4 is shown in the histogram as the single bell-shaped distribution with the 

highest pressure values. These four clusters were defined as the four steady-state modes for the 

loader-only PTO ‘on’ operation. The frequency counts of the four clusters were used to 

determine the relative proportion of time allocated to each steady-state mode. Finally, the 

average pump pressure in each cluster was normalized as a percentage of the maximum 

operating pump pressure rating for the pump used in the refuse truck (2500 psi). Thus, the 

loader-only PTO ‘on’ steady-state modes would be run at 12.87% of the rated maximum pump 

pressure for the loader for Mode 1, 38.26% of rated pressure for Mode 2, 52.84% of rated 

pressure for Mode 3, and 72.99% for Mode 4. 
FINAL REPORT 03-15777.14 25 of 38 

TABLE 15. CLUSTER ANALYSIS RESULTS FOR LOADER ONLY 

PTO “ON” OPERATION FOR REFUSE TRUCK 

Cluster 

(Mode) 

Total 

Available 

PTO Test 

Time, sec 

% Time 

at Mode 

Avg. Loader 

Pressure, psi

Min Loader 

Pressure, psi

Max Loader 

Pressure, psi 

Normalized 

Avg. Pump 

Pressure, 

% 

1 1310 7.17 321.65 150.71 603.03 12.87 

2 6698 36.64 956.50 603.94 1147.26 38.26 

3 7694 42.08 1320.95 1148.18 1614.25 52.84 

4 2581 14.12 1824.74 1616.13 2130.00 72.99 

The last analyses consisted of examining pressure data when both the compactor and 

loader were operating at the same time. Histograms of the collected pump pressure data were 

examined for the compactor and loader data to assist in defining the possible number of clusters 

for the simultaneous operation. Figure 15 illustrates a relative frequency histogram of the 

compactor pump pressure during the simultaneous PTO ‘on’ operation for the refuse truck. Note 

that the distribution of the pressure data for this operation was very similar to the one found in 

when the compactor was used alone. Figure 16 depicts the distribution of loader pump pressures 

during the simultaneous operation with the compactor. Again this looks very similar to the 

operation of the loader only pump pressure data. This may confirm that the two hydraulic loops 

operate independently regardless of whether they are working alone or in combination with one 

another. Table 16 lists the cumulative percentiles of the loader pump pressure data and the 

compactor pump pressure data for the refuse truck during simultaneous operation. Note that 

these percentiles are very closely related to the individual pump pressures for the compactor and 

loader found in Table 12 and Table 14, respectively. Lastly, Table 17 is a two way frequency 

table of the percent of total time spent at various combinations of pressure intervals for the 

compactor and the loader. Note that approximately 78% of the pressure data were collected 

when the compactor pressure was ≤ 350 psi. 
FINAL REPORT 03-15777.14 26 of 38 

FIGURE 15. REFUSE TRUCK COMPACTOR PRESSURE RELATIVE FREQUENCY 

HISTOGRAM FOR PTO “ON” OPERATION WHEN BOTH COMPACTOR AND 

LOADER WERE OPERATING 

FIGURE 16. REFUSE TRUCK LOADER PRESSURE RELATIVE FREQUENCY 

HISTOGRAM FOR PTO “ON” OPERATION WHEN BOTH COMPACTOR 

AND LOADER WERE OPERATING 
FINAL REPORT 03-15777.14 27 of 38 

TABLE 16. COMPACTOR AND LOADER PRESSURE PERCENTILES FOR TIME 

WHEN BOTH WERE IN OPERATION FOR REFUSE TRUCK TESTING 

Compactor Loader 

Percentile, % Pressure, psi Percentile, % Pressure, psi 

100 (max) 2155.75 100 (max) 2146.63 

95 651.35 95 1854.25 

90 455.50 90 1788.00 

80 358.03 80 1428.63 

70 327.68 70 1367.88 

60 306.54 60 1283.38 

50 285.39 50 1173.00 

40 264.24 40 1075.55 

30 238.49 30 991.90 

20 208.14 20 865.95 

10 173.20 10 573.60 

5 160.33 5 214.15 

0 (min) 150.21 0 (min) 150.71 

TABLE 17. PERCENT OF TOTAL TIME AT COMPACTOR AND LOADER 

PRESSURE WHEN BOTH ARE OPERATING FOR THE REFUSE TRUCK 

Compactor 

pressure, psi 

Loader Pressure, psi 

150-

350 

350.1-

550 

550.1-

750 

750.1-

950 

950.1-

1150 

1150.1-

1350 

1350.1-

1550 

1550.1-

1750 

1750.1-

1950 >1950 Total 

150-250 2.18 0.79 1.69 3.85 7.35 7.09 6.20 0.79 3.84 0.35 34.12 

250.1-350 2.24 0.90 1.76 4.99 10.77 8.10 8.95 0.75 4.72 0.69 43.87 

350.1-450 1.09 0.35 0.49 1.03 2.23 2.74 2.50 0.18 1.03 0.14 11.78 

450.1-550 0.53 0.05 0.14 0.41 0.58 0.50 0.39 0.06 0.28 0.02 2.96 

550.1-650 0.71 0.04 0.07 0.25 0.32 0.37 0.24 0.04 0.17 0.01 2.22 

650.1-750 0.52 0.01 0.07 0.16 0.28 0.16 0.14 0.03 0.08 0.02 1.46 

750.1-850 0.11 0.01 0.06 0.20 0.16 0.11 0.13 0.02 0.08 0.00 0.89 

850.1-950 0.04 0.02 0.02 0.11 0.13 0.14 0.09 0.02 0.06 0.00 0.64 

950.1-1050 0.02 0.01 0.03 0.11 0.08 0.07 0.05 0.02 0.05 0.00 0.44 

>1050 0.08 0.04 0.05 0.33 0.40 0.25 0.19 0.09 0.16 0.01 1.61 

Total 7.54 2.24 4.37 11.44 22.28 19.55 18.88 1.99 10.47 1.24 100 

 
FINAL REPORT 03-15777.14 28 of 38 

The final cluster analysis was performed using the compactor and loader pressures as 

cluster variables when both of these components were operating simultaneously. Analyses with 

up to 5 possible clusters were performed. These cluster analyses did not produce good results 

when all the data were used. Upon examination of a scatterplot of compactor and loader 

pressures it appeared that perhaps the very high levels of compactor pressures that were sparsely 

populated along the loader pressure range may have had an influence in identifying the clusters 

due to their very large distances from a cluster mean. Therefore, as an attempt to obtain 

adequate cluster definitions, only the compactor data <550 psi were used (this was approximately 

93% of the entire compactor and loader pressure data). This analysis resulted in four clusters as 

illustrated in Figure 17 and defined in Table 18. In Figure 17, the black dots represent the four 

cluster mean pressures while the four different colored ‘+’ symbols represent the compactor and 

loader pressures within an identified cluster. As can be seen in Table 18 the average compactor 

pressure for all four clusters is very close and that the loader pressures were more dominant in 

minimizing the distances of the pressures from the cluster average pressure. Also, the average 

loader pressures for the four clusters were very similar to the average pressures in the four 

clusters in the analysis of the loader only data. Upon consultation with EPA, it was decided to 

define four clusters with the same range of loader pressures as was identified in the loader only 

analysis and to compute the loader average for the four clusters using all the data collected when 

both the loader and compactor were in operation. It was also decided to compute the average 

compactor pressure over all the data collected when both the loader and compactor were in 

operation and to assign the compactor pressure average to all four clusters. The resulting steadystate modes for the simultaneous operation of the compactor and loader are listed in Table_19. 

Finally, the average compactor and loader pump pressure in each cluster was normalized as a 

percentage of the maximum operating pump pressure rating for the pump used in the refuse truck 

(2500 psi). Thus, the simultaneous operation of the compactor and loader PTO ‘on’ steady-state 

modes would be run at 12.81% of the rated maximum pump pressure for the compactor for all 

four modes. The loader would be run at 11.08% of the rated maximum pump pressure for Mode 

1, 38.18% for Mode 2, 53.42% for Mode 3, and 73.54% for Mode 4.
FINAL REPORT 03-15777.14 29 of 38 

FIGURE 17. CLUSTER ANALYSIS MEANS FOR REFUSE TRUCK 

WHEN BOTH LOADER AND COMPACTOR WERE OPERATING 

USING SELECTED DATA 

TABLE 18. CLUSTER ANALYSIS RESULTS FOR BOTH COMPACTOR 

AND LOADER PTO “ON” OPERATION FOR REFUSE TRUCK 

USING SELECTED DATA 

Cluster 

Avg. Compactor 

Pump Pressure, 

psi 

Avg. Loader Pump 

Pressure, psi 

Approx Loader 

Pressure Range, psi 

1 292.574 279.954 150-560 

2 275.697 940.789 561-1160 

3 279.927 1323.218 1161-1560 

4 271.900 1837.271 >1560 
FINAL REPORT 03-15777.14 30 of 38 

TABLE 19. FINAL STEADY-STATE MODES FOR BOTH COMPACTOR 

AND LOADER PTO “ON” OPERATIONS FOR THE REFUSE 

TRUCK USING ALL DATA 

Mode 

% 

Time 

at 

Mode 

Avg. 

Compactor 

Pump 

Pressure, 

psi 

Avg. 

Loader 

Pump 

Pressure, 

psi 

Max 

Compactor 

and Loader 

Pump 

Pressure, 

psi 

Normalized 

Avg. 

Compactor 

Pump 

Pressure, 

% 

Normalized 

Avg. 

Loader 

Pump 

Pressure, 

% 

1 10.31 320.33 277.03 2500 12.81 11.08 

2 37.42 320.33 954.05 2500 12.81 38.16 

3 39.00 320.33 1335.61 2500 12.81 53.42 

4 13.27 320.33 1838.38 2500 12.81 73.54 

 
FINAL REPORT 03-15777.14 31 of 38 

5.0 TASK 4 - DUTY CYCLE DEVELOPMENT 

This task involved the development of a composite duty cycle for EPA PTO testing using 

both the duty cycle information from the utility boom truck and the ASL refuse truck as defined 

in Task 3. Upon EPA recommendation, the duration of the composite cycle was targeted to be 

approximately 10 minutes. Data and information collected in Task 1 were used in weighting 

different portions of the composite duty cycle in order to reflect actual field PTO operations in 

the population according to usage of utility truck for ASL refuse truck. Table 20 identifies the 

amount of time each vehicle type and application would be included in a 10-minute composite 

duty cycle. 

TABLE 20. COMPOSITE 10-MINUTE CYCLE TIMES BY 

VEHICLE AND APPLICATION 

Vehicle 

Population 

Weighting 

% Application 

Application 

Weighting 

% 

Composite 

Cycle 

Weighting 

% 

Composite 

Cycle Time 

(min) 

Composite 

Cycle Time 

(sec) 

Utility 

Truck 60 Rural 20 12 1.2 72 

Urban 80 48 4.8 288 

Refuse 

Truck 40 Residential 100 40 4.0 240 

The weightings and composite cycle time for each vehicle application were applied to the 

information for each vehicle mode identified in Task 3 from the usage data analyses. Table 21 

lists the amount of actual time allotted to each of these vehicle modes assuming a 10-minute 

composite duty cycle. The next step was to decide if the times allotted to each mode by vehicle 

application were to be applied entirely during one testing sequence or if they were to be divided 

into repetitive ‘cycles’. For the utility truck application, its operation warranted a single 

continuous test time for each mode as it reflected how the utility operation functions. But the 

idle times associated with the rural and urban usage were divided in half so that the utility truck 

operations started and ended with idle time. 

Conversely, the refuse truck loader and compactor operations did represent usage that 

was cyclic in nature. The loader cycle characterized the picking up of the refuse receptacle, 

raising it to the truck, emptying the contents and replacing it to the ground. This process was 

repeated throughout the day as the refuse truck performed its duties. Therefore, a discrete 

Fourier transform using the fast Fourier transform (FFT) algorithm was performed on the loader 

and compactor data independently. The results of the FFT from the compactor data are shown 

in Figure 18. It can be seen that there is more than one frequency present. For this test cycle, 

0.025 Hz was chosen due the high strength and matching closely to what was observed visually 

in the raw data files. The FFT results for the loader, Figure 19, are less clear. There is not a 

distinct peak, but the highest strength varies from 0.01 Hz to 0.03 Hz. The total time for the 

compactor –only operation, with idle, was calculated to be 74 seconds. The period of the 

compactor cycle was 40 seconds, so it was decided to divide the compactor operation by two 

instead of increasing the cycle time to 80 seconds. For simplicity and lack of better evidence, it 

was decided to use two ‘cycles’ for loader only, compactor only, and both loader and compactor 
FINAL REPORT 03-15777.14 32 of 38 

modes in order to comply with the total test times associated with the modes identified for the 

refuse truck. More cycles could be added but the resulting composite duty cycle time would also 

increase. 

FIGURE 18. FFT PLOT FOR REFUSE TRUCK COMPACTOR OPERATION 

FIGURE 19. FFT PLOT FOR REFUSE TRUCK LOADER OPERATION 

0 0.01 0.02 0.03 0.04 0.05 0.06

0

2

4

6

8

10

12

x 10-3

Compactor Frequency, Hz

Strength

0 0.01 0.02 0.03 0.04 0.05

0

0.005

0.01

0.015

0.02

0.025

0.03

0.035

0.04

Loader Frequency, Hz

Strength
FINAL REPORT 03-15777.14 33 of 38 

TABLE 21. COMPOSITE 10-MINUTE CYCLE TIMES FOR EACH MODE 

Vehicle Application Mode 

% Time at 

Mode 

Composite 

Cycle Time 

(sec) 

Computed 

Time at 

Mode, sec 

Actual 

Time at 

Mode, sec 

Utility 

Rural 1 9.66 72 6.96 7 

2 (Idle) 90.34 72 65.04 65 

Urban 1 49.89 288 143.68 144 

2 (Idle) 50.11 288 144.32 144 

Refuse 

Loader 

Only 

1 7.17 240 3.78 4 

2 36.64 240 19.35 20 

3 42.08 240 22.23 22 

4 14.12 240 7.46 8 

5 (Idle) 10.65 240 25.57 26 

Compactor 

Only 

1 83.41 240 51.97 52 

2 16.59 240 10.33 10 

3 (Idle) 10.65 240 25.57 26 

Both 

Loader and 

Compactor 

1 10.31 240 4.97 4 

2 37.42 240 18.03 18 

3 39.00 240 18.78 18 

4 13.27 240 6.39 6 

5 (Idle) 10.65 240 25.57 26 

Total Time, sec 600 

Table 22 lists the proposed 10-minute composite duty cycle for the PTO operation based 

on the analysis of the data collected on the utility truck and ASL refuse truck. 

 
FINAL REPORT 03-15777.14 34 of 38 

TABLE 22. FINAL COMPOSITE 10-MINUTE PTO DUTY CYCLE 

Time, 

sec

Utility Truck 

or Refuse 

Compactor 

Pump 1

Refuse 

Loader 

Pump 2 Vehicle Application Mode Time (sec)

0-32 0 0 Utility Rural 2 (Idle) 32 (1/2 of total idle time)

33-39 80.45 0 Utility Rural 1 7

40-72 0 0 Utility Rural 2 (Idle) 33 (1/2 of total idle time)

73-144 0 0 Utility Urban 2 (Idle) 72 (1/2 of total idle time)

145-288 83.47 0 Utility Urban 1 144

289-360 0 0 Utility Urban 2 (Idle) 72 (1/2 of total idle time)

361-362 0 13 Refuse Loader 1 2

363-372 0 38 Refuse Loader 2 10

373-383 0 53 Refuse Loader 3 11

384-387 0 72.99 Refuse Loader 4 4

388-400 0 0 Refuse Loader 5 (idle) 13

401-402 0 13 Refuse Loader 1 2

403-412 0 38 Refuse Loader 2 10

413-423 0 53 Refuse Loader 3 11

424-427 0 72.99 Refuse Loader 4 4

428-440 0 0 Refuse Loader 5 (idle) 13

441-466 11.24 0 Refuse Compactor 1 26

467-471 29.28 0 Refuse Compactor 2 5

472-484 0 0 Refuse Compactor 3 (idle) 13

485-510 11.24 0 Refuse Compactor 1 26

511-515 29.28 0 Refuse Compactor 2 5

516-528 0 0 Refuse Compactor 3 (idle) 13

529-530 12.81 11.08 Refuse Compactor 

and Loader 1 2

531-539 12.81 38.162 Refuse Compactor 

and Loader 2 9

540-548 12.81 53.42 Refuse Compactor 

and Loader 3 9

549-551 12.81 73.53 Refuse Compactor 

and Loader 4 3

552-564 0 0 Refuse Compactor 

and Loader 5 (idle) 13

565-566 12.81 11.08 Refuse Compactor 

and Loader 1 2

567-575 12.81 38.162 Refuse Compactor 

and Loader 2 9

576-584 12.81 53.42 Refuse Compactor 

and Loader 3 9

585-587 12.81 73.53 Refuse Compactor 

and Loader 4 3

588-600 0 0 Refuse Compactor 

and Loader 5 (idle) 13
FINAL REPORT 03-15777.14 35 of 38 

6.0 TASK 5 - TEST RIG RESEARCH AND DEVELOPMENT 

 A hydraulic system simulator has been designed, but not built or tested, that may 

enable the simulation of the hydraulic load on the pumps of a refuse hauler while conducting 

chassis dyno testing of the vehicle. The simulator circuit schematic, shown in Figure 20, consists 

of two parallel circuits so that an individual load can be applied to each pump of a tandem pump 

system. 

FIGURE 20. HYDRAULIC SYSTEM SIMULATOR CIRCUIT SCHEMATIC 

 

From Vehicle

Pump #1

From Vehicle

Pump #2

Return to 

Vehicle 

Hydraulic 

Reservoir

FM 1 FM 2

P1 P2

PC1 PC2

BV1 BV2
FINAL REPORT 03-15777.14 36 of 38 

 The outlet port for each pump must be disconnected from the system and attached to each 

line going to the hydraulic system simulator. The disconnected pump outlet lines must be 

capped off. The return line from all the system control valves to the system hydraulic reservoir 

must also be intercepted, before the system hydraulic cooling system and before any return line 

filtration. This line can be intercepted by “T’ing” into the return line. The return line from the 

system simulator should be attached to this “T”. Alternatively, instead of a “T”, the return from 

the system control valves can be disconnected and capped and the hydraulic simulator can be 

connected to the return system on the vehicle. 

 The operation of each leg of the circuit, shown in Figure 20, is identical. The following 

discussion will be for the circuit for Pump #1, but applies similarly to the circuit for Pump #2. 

During normal no-load operation, to simulate when the hydraulic system is in Neutral, none of 

the valves are activated and flow from the Pump #1 passes through the Bypass Valve, BV1, and 

then returns back to the vehicle with very little backpressure on the pump. The Bypass Valve is a 

normally open, solenoid operated valve, so in this condition, it should not be activated. The flow 

rate from Pump #1 is measured by the Flow Meter, FM 1, and the pressure on the pump is 

measured by the Pressure Transducer, P 1. 

 The hydraulic system simulator simulates a load by diverting the pump flow through a 

proportional electro-hydraulic relief valve. The electronic control signal is first applied to the 

Pressure Control valve, PC 1, and then the Bypass Valve should be activated. The Pressure 

Control valve regulates the pressure in the line from the pump in proportion to the electronic 

control signal. Prior to testing, the Pressure Control valve should be calibrated to determine the 

proper control signal at a given flow rate that will result in the desired pressure the needs to be 

simulated. Better control accuracy can be obtained by employing a closed loop control on 

pressure. 

 Hydraulic valves for the simulator have been selected. The supplier is Sun Hydraulics 

and a list of the required valves is below: 

Description Part No. Quantity

2‐Way, Poppet Directional Valve with in‐line body DFEA‐8DN‐IEN 2

2‐Way, Solenoid Operated Directional Spool‐Pilot, w/ 12V  Coil DAA‐MHN‐712 2

Pilot Operated, balanced piston relief main stage with in‐line body RPIC‐8WN‐IEN 2

Electro‐proportional relief valve‐Pilot with imbedded amplifier RBAP‐XAN‐4A12V 2

Hand Held Programmer 991‐700 1

Cable for Programmer 991‐702 1

 These valves are screw in type cartridge valves. They require a body, or manifold to 

screw into. Line mounted bodies are included in the part number for the respective valves. These 

valves would then need to be plumbed together with appropriate fittings to create the circuit 

shown in Figure 21. An alternate approach would be to have a custom manifold fabricated that 

would duplicate the circuit shown in the box in Figure 20. This manifold would be much more 

compact and simple. 

 
FINAL REPORT 03-15777.14 37 of 38 

 The proportional pressure control valve includes an integral digital amplifier. It requires 

a hand held programmer to configure the amplifier. The amplifier converts a low level analog 

signal to a higher power current to power the proportional solenoid. 

 
FINAL REPORT 03-15777.14 38 of 38 

7.0 SUMMARY 

The Environmental Protection Agency (EPA) requested Southwest Research Institute 

(SwRI) to evaluate engine and vehicle performance of utility vehicles and refuse haulers for 

boom operation. SwRI performed a literature search and interviewed various industry contacts 

to determine which vehicles’ PTO systems might be hybridized in significant quantities in 2011 

and beyond. SwRI determined that there were currently only two types of vehicles meeting 

those requirements, utility boom trucks and automated side loader (ASL) refuse haulers. 

SwRI obtained permission to instrument a utility boom truck in two different locations, 

urban and rural, and an ASL refuse truck operating in a suburban area. A data acquisition 

system was installed on each truck to record data from transducers measuring PTO hydraulic 

pressure and flow and engine speed, engine load, engine fuel rate, and vehicle speed from the 

vehicle’s J1939 network. 

In-field hydraulic pressure data were collected over a period of several days using two 

application-specific vehicles: utility and refuse trucks. Definitions of power take-off (PTO) 

operations were identified as (1) pump “on” and idle (utility truck), and (2) compactor only, 

loader only, both compactor and loader, and idle (refuse truck). Steady-state pressure modes 

were identified by a statistical disjoint cluster analysis. Statistical frequency analyses of the infield data were used to determine the relative proportion of time allocated to each steady-state 

mode. Information collected on population usage was used to weight different portions of the 

composite duty cycle (utility and refuse truck cycles) to reflect actual field PTO operations. 

A test rig was designed to test vehicle PTO systems according to the test cycle’s 

specifications. The design uses off-the-shelf parts and includes two test circuits to accommodate 

vehicles equipped with two independent hydraulic circuits. The system has not been built or 

tested, but principle of operation should allow others with hydraulic system experience build a 

system to meet the test cycle specifications.