Reflective Measurement Systems – RetroTek-MU Mobile Pavement Marking Retroreflectometer Evaluation

Report prepared by

Adam Pike, P.E. Associate Research Engineer

College Station, Texas

Report Prepared for Reflective Measurement Systems

January 2019

DISCLAIMER

This project was performed by the Texas A&M Transportation Institute. The contents of this report reflect the views of the authors, who are responsible for the facts and the accuracy of the data presented herein. The contents do not necessarily reflect the official view or policies of any State or Federal agency. This report does not constitute a standard, specification, or regulation. The Texas A&M Transportation Institute does not endorse products or manufacturers. Trade or manufacturers’ names appear herein solely because they are considered essential to the object of this report.

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TABLE OF CONTENTS

Page

List of Figures ...... iii

List of Tables ...... iii

Chapter 1: Work Plan ...... 1 Data Collection ...... 1 Variables Evaluated ...... 1 Data Collection Procedures ...... 2 Open Testing ...... 2 Closed Course Testing ...... 3

Chapter 2: Testing Results ...... 6 Open Road Testing Results ...... 6 Mobile and Portable Data Comparison ...... 6 Impact of Marking Color and Pattern ...... 7 Impact of Measurement Position and Calibration Level ...... 8 Closed Course Testing Results ...... 9 Mobile and Portable Data Comparison ...... 10 Impact of Marking Color and Pattern ...... 13 Impact of RRPMs ...... 14

Chapter 3: Summary of Findings ...... 15

Appendix: Images of Test Areas ...... 16

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LIST OF FIGURES

Figure 1. RetroTek-MU in Operation with LED (Green) Illuminating the Pavement ...... 2 Figure 2. Open Road Portable vs. Mobile Data...... 7 Figure 3. Closed Course Portable vs. Mobile Data...... 13 Figure 4. Villa Maria Test Area...... 16 Figure 5. Jones Road Test Area...... 16 Figure 6. Leonard Road Test Area...... 17 Figure 7. State 47 Test Area...... 17 Figure 8. Farm to Market 60 Test Area...... 18 Figure 9. Closed Course Test Area Marking Examples Part I...... 18 Figure 10. Closed Course Test Area Marking Examples Part II...... 19 Figure 11. Structured Marking Test Area...... 19 Figure 12. Preformed Tape Pavement Marking Test Area...... 20

LIST OF TABLES

Table 1. Open Road Test Marking Information...... 3 Table 2. Closed Course Marking Information...... 4 Table 3. Open Road Test Results...... 7 Table 4. Open Road Marking Color and Pattern Error Results...... 8 Table 5. Position and Calibration Level Testing Results...... 9 Table 6. Comparison of Position and Calibration Level Percent Change...... 9 Table 7. Closed Course Test Area Data...... 11 Table 8. Closed Course Preformed Tape Test Area Data...... 12 Table 9. Closed Course Color and Marking Pattern Error Results...... 14 Table 10. RRPM Test Area Results...... 14

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CHAPTER 1: WORK PLAN

This report describes the Texas A&M Transportation Institute (TTI) evaluation of the Reflective Measurement Systems – RetroTek-MU mobile pavement marking retroreflectometer. The evaluation was conducted to quantify the accuracy of the data captured by the retroreflectometer. The performance measure under evaluation was the measured coefficient of 2 retroreflected luminance (retroreflectivity), RL, (mcd/m /lux) of a variety of pavement markings under various conditions. The details of the data collection are described in this chapter.

DATA COLLECTION Data collection occurred during typical operation of the RetroTek-MU system at highway speeds. Data were collected at the Texas A&M University RELLIS Campus and on public around the Texas A&M University Campus. The RetroTek-MU system was operated by a contractor. A TTI representative rode in the test to direct the operator where to test and under what conditions.

Variables Evaluated There are numerous factors that can impact the ability of a mobile retroreflectometer to accurately evaluate the retroreflectivity of a pavement marking. The evaluated factors included in the testing are listed and described below.  Retroreflectivity Level: Evaluated markings across a range of retroreflectivity levels.  Marking Color: Evaluated white and yellow markings.  Line Type: Evaluated solid and broken lines.  Marking Type: Evaluated different types of marking materials.  : Evaluated markings on , , and chip seal surfaces.  Drive Position Sensitivity: Evaluated the same markings at different positions within the measurement window (width of measurement field for the system).  Raised Retroreflective Pavement Marker (RRPM) Impact: Evaluated similar markings with and without RRPMs.

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Data Collection Procedures Data were only collected at night due to the design and operational requirements of the RetroTek-MU system. Data were only collected in dry conditions. All RetroTek-MU data were collected during one night of operation. The comparison portable retroreflectometer readings were collected the same day and the day after the RetroTek-MU data collection. The RetroTek- MU system is center mounted on the front of the vehicle. This allows the system to evaluate two lines of markings (single or double lines), on the vehicle’s left and on the vehicle’s right, and all in- markings at the same time. The RetroTek-MU evaluates the markings at the standard 30-meter geometry. Figure 1 provides an example of the system illumination at night. The general methodology for the various sets of data collected are described below.

Figure 1. RetroTek-MU in Operation with LED (Green) Illuminating the Pavement in Front of the Vehicle.

Open Road Testing The open road testing consisted of evaluating 13 different pavement markings under various conditions. The open road test area pavement markings varied in length from approximately 0.25 to 1.0 miles long and consisted of both white and yellow, and solid and broken line pavement markings. The road surface types consisted of faded asphalt, dark asphalt, and chip seal. The nighttime testing took place on rural roads with no overhead lighting and minor impacts from . Table 1 describes each marking test area. Data collection directions are indicated in the section names as follows, eastbound (EB), westbound (WB), northbound (NB), and southbound (SB). The Appendix provides images of the open road test areas. The FM 60 test area was a 1-mile test section that was used to evaluate the impact of lane position and calibration factor on the data collection. Multiple runs each with the evaluation in

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the center position, left in lane position, and right in lane position were recorded on the test section. The left and right drive position was maintained at a location where the measurement of the marking was close to the outer edge of the allowable measurement window. With the exception of the FM 60 test area, the markings on the open road test area were evaluated at regular intervals with a portable retroreflectometer along the entire length of the marking. The portable retroreflectometer was properly calibrated prior to the data collection. The measurement interval was approximately 40 feet. All portable measurements were taken in representative locations along the length of the markings. The goal was to get a representative value for the retroreflectivity average of the marking and for the retroreflectivity trend along the length of the marking for comparison to data collected with the RetroTek-MU. The mobile data collected at the FM 60 test area was compared to itself for the differing data collection scenarios. Table 1. Open Road Test Marking Information. Section Name Line Type Road Surface Marking Material Color Bead Type EB Villa Maria Solid Chip Seal Thermoplastic White Small Rd EB Villa Maria Broken Chip Seal Thermoplastic Yellow Small Rd WB Villa Maria Solid Chip Seal Thermoplastic White Small Rd WB Villa Maria Broken Chip Seal Thermoplastic Yellow Small Rd NB Jones Rd Solid Faded Asphalt White Small NB Jones Rd Double Solid Faded Asphalt Paint Yellow Small WB Leonard Rd Solid Chip Seal Thermoplastic White Small WB Leonard Rd Broken Chip Seal Thermoplastic Yellow Small NB SH 47 Solid Chip Seal Thermoplastic Yellow Small SB SH 47 Solid Chip Seal Thermoplastic Yellow Small SB SH 47 Broken Chip Seal Thermoplastic White Small EB FM 60 Solid Dark Asphalt Thermoplastic White Small EB FM 60 Broken Dark Asphalt Thermoplastic White Small

Closed Course Testing The closed course testing occurred at the Texas A&M University RELLIS Campus. The RELLIS Campus is the site of a former airfield and thus has a series of runways and taxiways. One of the runways is the site of the TTI mobile pavement marking retroreflectometer certification program test area. This runway has numerous test markings that can be evaluated and manipulated in a controlled environment. The closed course pavement markings are

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approximately 0.35 miles in length and consisted of both white and yellow, solid, double, and broken line pavement markings. The markings evaluated during the closed course testing were typical marking types found on roadways. These markings consisted of paint, epoxy, preformed tape and thermoplastic binders with standard big and small beads, high refractive index glass beads, and microcrystalline ceramic beads. Three markings were evaluated with RRPMs present, and after the RRPMs had been obscured. The RRPMs were placed at 80-foot spacing along the entire length of the test area. Structured thermoplastic markings and preformed tape markings were also evaluated. The structured thermoplastic markings were evaluated in both directions. The preformed tape markings consisted of three yellow and three white test areas with varying retroreflectivity levels. The preformed tape test areas were evaluated in both directions. Considering the multiple directions evaluated and the multiple preformed tape test areas, a total of 28 different markings were evaluated. Table 2 describes each marking. The Appendix provides images of the closed course test areas. Table 2. Closed Course Marking Information. Line Name Line Type Marking Material Color Bead Type Line 2 Broken Epoxy Yellow Big and Small Line 3 Solid Epoxy White Big and Small Line 8 Broken Thermoplastic White Small Line 10 Solid Paint Yellow Small Line 15 Broken Paint Yellow Small Line 16 Broken Paint White Small Line 17 Solid Thermoplastic Yellow Small Line 18 Broken Epoxy White Big and Small Line 24 Solid Paint White Small Line 29 Solid Thermoplastic Yellow Small Line 39 Broken Epoxy Yellow Big and Small Line 40 Solid Epoxy White Big and Small Small (High Structure 2 Solid Thermoplastic White Refractive Index) Structure 3 Solid Thermoplastic White Small Preformed Microcrystalline Solid Preformed Tape White Tape Ceramic Preformed Microcrystalline Solid Preformed Tape Yellow Tape Ceramic

The markings on the closed course were evaluated at regular intervals with a portable retroreflectometer along the entire length of the marking. The measurement interval was

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approximately 15 feet on solid lines and two measurements per line segment on broken lines. All portable measurements were taken in representative locations along the length of the markings. The goal was to get a representative value for the retroreflectivity average of the marking and for the retroreflectivity trend along the length of the marking for comparison to the RetroTek-MU system.

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CHAPTER 2: TESTING RESULTS

In total, 42 tests were conducted, which resulted in the evaluation of 91 pavement marking segments. Some tests evaluated two markings, one marking on the left and one on the right side of the vehicle simultaneously. Some tests only evaluated a single marking at a time. The preformed tape evaluations had three markings on each side of the vehicle in consecutive evaluation sections. TTI oversaw the mobile data collection and received the results from the contractor and equipment manufacturer once they were processed. Each individual marking evaluation was processed and analyzed. Where necessary, data were trimmed to best match the specific locations for the comparison retroreflectivity data. The results of the open road and closed course testing are described in the following sections.

OPEN ROAD TESTING RESULTS The objectives of the open road tests were to: 1) compare mobile data to portable data across a range of marking retroreflectivity levels; 2) evaluate the impact of marking color and pattern; and 3) evaluate the impact of measurement position and the impact of the high or low calibration level parameter.

Mobile and Portable Data Comparison The open road testing evaluated 13 pavement marking areas. Portable readings (TTI data) were taken on 11 of these sections. Table 3 provides the mobile and portable results for these section. The table shows that the average systematic error is −5.7 percent with an average random error of 8.7 percent. Figure 2 shows the portable averages versus the mobile averages for the 11 test areas where portable measurements were taken. A linear trend line shows how the data relates (blue dashed line), and a line of equality (red dotted line) is also provided. The slope of the line is nearly 1, and the coefficient of determination (R2) is 0.9417.

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Table 3. Open Road Test Results. Percent Error from

Portable Test RetroTek RetroTek TTI (RL) TTI (RL) Left Right Section Left Right # (RL) Left (RL) Right Left Right White 23 - SB SH 47 287 - 291 - −1.5 - Broken Yellow White EB Villa 33 140 223 133 259 5.5 −13.8 Broken Solid Maria Rd Yellow White WB Villa 34 129 256 126 292 2.1 −12.4 Broken Solid Maria Rd Yellow White NB Jones 35 90 / 90 159 115 / 99 158 −21.7 / −9.1 0.8 Double Solid Solid Rd Yellow White WB 36 181 341 205 317 −11.6 7.6 Broken Solid Leonard Rd 37 Yellow Solid - NB SH 47 200 - 232 - −13.8 - White 38 Yellow Solid SB SH 47 164 301 182 291 −9.9 3.6 Broken

400

350

300

/lux) 2 250

200

150 y = 0.9358x + 23.316 R² = 0.9417

PortableRetro (mcd/m 100

50

0 0 50 100 150 200 250 300 350 400 RetroTek-MU Mobile Retro (mcd/m2/lux)

Figure 2. Open Road Portable vs. Mobile Data.

Impact of Marking Color and Pattern The data provided in Tables 3 and 4 were used to determine the impact of marking color and marking pattern on the results. Table 4 presents the average error, both systematic and

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random, for each of the conditions evaluated. The average error for each individual marking was averaged with the rest of the markings that fit the given grouping. The markings were grouped by color and pattern. There were six white and seven yellow evaluations. There were eight solid line and five broken line evaluations. The results from Table 4 show that for any of the conditions evaluated the error was approximately 11 percent or less. It appears that yellow and solid markings have larger error than white or broken markings. There were limited runs, with as few as five runs total making up the subgroups of data. This results in individual tests having a larger influence on the data. The color and pattern will also be evaluated during the closed course evaluation. There did not appear to be any specific influence of the varying pavement surfaces on the readings. Table 4. Open Road Marking Color and Pattern Error Results.

Sum of Average Values Sum of Absolute Average Condition (Systematic Error) Values (Random Error)

White Markings Average Percent Error −2.6 6.6 Yellow Markings Average Percent Error −8.4 10.5 Solid Markings Average Percent Error −9.0 11.2 Broken Markings Average Percent Error −0.4 4.9

Impact of Measurement Position and Calibration Level The FM 60 test area was used to test the impact of measurement position and calibration level on the mobile readings. Table 5 presents the results of the measurement position and calibration level data collection. All runs were conducted at 70 mph besides one test that was conducted at 55 mph. There was no significant difference between the results of the two speeds. The position of the measurements relates to the vehicle position in the lane. The driver attempted to keep the marking that was farther away from the vehicle within the measurement field of the mobile retroreflectometer. Operators would normally drive in the center of the lane and not purposely close to the edge or center line. Ultimately some data were lost at various times due to too far away from the marking. This may impact the overall average as the pavement markings are not perfectly consistent along their length. The calibration level is a selectable parameter in the operating software that helps the system better evaluate markings with high or low retroreflectivity levels. The markings on this test area were near the threshold level for using the high calibration level.

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Table 5. Position and Calibration Level Testing Results. Left Right RetroTek RetroTek Test # Section Notes Speed Position Marking Marking Left (RL) Right (RL) White White Low RL 24 EB FM 60 70 Middle 454 529 Broken Solid Calibration White White Low RL 25 EB FM 60 70 Middle 449 528 Broken Solid Calibration White White High RL 26 EB FM 60 70 Middle 495 564 Broken Solid Calibration White White High RL 27 EB FM 60 55 Middle 499 567 Broken Solid Calibration White White High RL 28 EB FM 60 70 Right 460 538 Broken Solid Calibration White White High RL 29 EB FM 60 70 Left 503 492 Broken Solid Calibration White White High RL 30 EB FM 60 70 Right 453 521 Broken Solid Calibration White White High RL 31 EB FM 60 70 Left 521 522 Broken Solid Calibration White White High RL 32 EB FM 60 70 Middle 495 568 Broken Solid Calibration

Table 6 presents the percent change for the various test conditions as compared to the

high RL calibration with the middle driving position. The measurements at the left or right in- lane positions differed by approximately 10 percent or less when compared to the center of the

lane position. The low RL resulted in data that was between 6 and 9 percent lower on average

than data collected with the high RL setting. Table 6. Comparison of Position and Calibration Level Percent Change. Percent Change from High RL Calibration

Middle Position Average RL Average RL Calibration and Position Left Right Left Right

Low RL Calibration Middle 452 528 −8.9 −6.7

High RL Calibration Middle 496 566 0.0 0.0

High RL Calibration Left 512 507 3.2 −10.6

High RL Calibration Right 456 530 −8.0 −6.5

CLOSED COURSE TESTING RESULTS The objectives of the closed course tests were to: 1) compare mobile data to portable data across a range of marking retroreflectivity levels; 2) evaluate the impact of marking color and pattern; and 3) evaluate the impact of RRPMs.

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Mobile and Portable Data Comparison The closed course testing evaluated 20 different pavement markings, some of which were evaluated in both directions. Portable retroreflectivity measurements (TTI data) were taken on all these markings but results from four of the sections are not included in this portion of the analysis, because those sections were designated for the evaluation of the impact of RRPM presence on the readings. Table 7 and Table 8 provide the data results from the closed course mobile and portable comparison. The tables were developed to show the error between the RetroTek-MU mobile retroreflectivity data and the TTI portable measurement data. Additional information on the markings can be found in the previous chapter. The majority of the mobile data were within 10 percent of the portable data. The average systematic error was 0.9 percent, with an average random error of 5.7 percent. Not all test areas evaluated markings on the left and right. Some sections showed higher error, but this larger error can partially be explained. Structure marking 3 is a lower retro structure marking and also had high variability of the readings. The nature of structure markings will generally result in them having slightly different mobile measurements compared to portable due to the geometry of the evaluations. Portable measurements are evaluated in a 30-meter coplanar geometry, whereas the mobile measurements are 30-meter geometry, but are not coplanar due to the lateral offset of the mobile device from the pavement marking. The center mounted RetroTek-MU system may see larger error than side mounted mobile retroreflectometer when evaluating structured markings due to the greater lateral offset. This needs to be considered or compensated for when collecting data on structured markings. Preformed tape white marking 2 also showed larger than typical error. This is due to the low retroreflectivity values and variable values along the length of the marking. There were numerous portable measurements that were very low and likely not included with the mobile data due to low signal to noise. All mobile retroreflectometers will struggle to accurately evaluate pavement markings when the retroreflectivity values get very low due to their inability to capture all the low readings.

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Table 7. Closed Course Test Area Data. Percent Error from

Portable Test Left Right Left Right RetroTek RetroTek TTI (RL) TTI (RL) Left Right # Marking Marking Marking Marking (RL) Left (RL) Right Left Right Yellow 2 - 29 - 157 - 140 - 12.2 - Solid White 3 - - 24 - 236 - 242 - −2.3 Broken White 4 - 18 - 338 - 341 - −0.8 - Broken White White 5 16 18 227 360 245 341 −7.3 5.7 Broken Broken Yellow −17.7/ 6 Double - 17 - 114/118 - 139/122 - - −3.3 Solid Yellow Yellow 7 Double 15 17 110 122/127 109 139/122 1.0 −12.0/4.1 Broken Solid White 8 - - 16 - 238 - 245 - −3.0 Broken Yellow 9 - 10 - 116 - 111 - 4.6 - Solid White Yellow 10 8 10 209 117 216 111 −3.3 5.0 Broken Solid White 11 - - 8 - 213 - 216 - −1.5 Broken White White Structure Structure 15 140 1191 116 1123 20.8 6.1 Solid Solid 3 2 White White Structure Structure 16 686 167 697 125 −1.6 33.3 Solid Solid 2 3 White White Structure Structure 17 138 1241 116 1123 18.8 10.6 Solid Solid 3 2 White White Structure Structure 18 715 160 697 125 2.5 28.4 Solid Solid 2 3

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Table 8. Closed Course Preformed Tape Test Area Data. RetroTek Data / TTI Data Percent Error from Portable Left Right Left Right Left Right Left Right Left Right Left Right Test Left Right Travel Marking Marking Marking Marking Marking Marking Marking Marking Marking Marking Marking Marking # Marking Marking Direction #1 #1 #2 #2 #3 #3 #1 #1 #2 #2 #3 #3 Yellow White 222 / 478 / 19 NB 96 / 93 116 / 101 81 / 62 861 / 915 3.2 14.9 −1.8 30.6 2.8 −5.9 Solid Solid 226 465 White Yellow 810 / 105 / 20 SB 497 / 453 72 / 62 248 / 247 104 / 99 -9.5 9.7 16.1 0.4 −1.9 5.1 Solid Solid 895 107 Yellow White 221 / 504 / 21 NB 97 / 93 116 / 101 79 / 62 876 / 915 4.3 14.9 −2.2 27.4 8.4 −4.3 Solid Solid 226 465 White Yellow 805 / 103 / 22 SB 492 / 453 72 / 62 247 / 247 104 / 99 -10.1 8.6 16.1 0.0 −3.7 5.1 Solid Solid 895 107

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Figure 3 shows the portable averages versus the mobile averages for the 39 included evaluations. The evaluations for the structure 3 marking and preformed tape marking 2 white were not included due to the previously noted issues. A linear trend line (blue dashed line) shows how the data relate. The slope of the line is nearly 1, and the coefficient of determination (R2) is 0.9878. A line of equality (red dotted line) is also provided. The mobile and portable data closely match each other with almost no bias as the line of equality and data trend lines are nearly on top of each other.

1400

1200

1000

/lux) 2

800

y = 0.9851x + 3.7963 600 R² = 0.9878

400 Portable Retro Retro Portable (mcd/m

200

0 0 200 400 600 800 1000 1200 1400 RetroTek-MU Mobile Retro (mcd/m2/lux)

Figure 3. Closed Course Portable vs. Mobile Data.

Impact of Marking Color and Pattern

The data provided in Table 7 and Table 8 were used to determine the impact of marking color and marking pattern. Data from the structure 3 marking and preformed tape section 2 white were not included in this analysis due to the previously noted issues. Table 9 presents the average error, both systematic and random, for each of the conditions evaluated. The markings were grouped by color and pattern. There were 19 white and 20 yellow evaluations. There were 31 solid line and 8 broken line evaluations. The average error for each individual marking evaluation was averaged with the rest of the markings that fit the given grouping. The results indicate that there is no clear bias based on marking color or pattern. The average error was less

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than 7 percent for any color or marking pattern. The type of marking evaluated did not appear to impact the results. Table 9. Closed Course Color and Marking Pattern Error Results. Sum of Average Values Sum of Absolute Average Condition (Systematic Error) Values (Random Error) White Markings Average Percent Error 0 5.8 Yellow Markings Average Percent Error 1.9 5.6 Solid Markings Average Percent Error 1.6 6.3 Broken Markings Average Percent Error −1.4 3.1

Impact of RRPMs The closed course testing allowed for a controlled test of three markings that had RRPMs installed. These three markings (lines 2, 3, and 39) were evaluated with the RRPMs exposed and with the RRPMs obscured with masking tape so they would not reflect, resulting in a condition with no RRPMs present. Table 10 presents the results of the testing with and without RRPMs on the three markings. The difference between the measurements with and without the RRPMS was less than 3 percent different on average. The left markings (lines 2 and 39) averaged −16.1 percent error with RRPMs present and −18.8 percent error without the RRPMs. The right marking (line 3) with RRPMs averaged 6.1 percent difference, and 6.8 percent difference without the RRPMs. The right marking (line 40) without RRPMs directly on the line averaged 0.0 percent error when RRPMs were present on the left line, and 1.0 percent error when no RRPMs were present on the left line. Table 10. RRPM Test Area Results. Percent Error from Portable Test Left Right RetroTek RetroTek TTI (RL) TTI (RL) # Notes Marking Marking (RL) Left (RL) Right Left Right Left Right 1 RRPMs on left 39 40 161 206 190 209 −15.1 −1.4 RRPMs on left 12 and right 2 3 192 424 234 402 −18.0 5.5 RRPMs on left 13 and right 2 3 197 429 234 402 −15.6 6.7 14 RRPMs on left 39 40 160 212 190 209 −15.7 1.4 40 No RRPMs 39 40 155 210 190 209 −18.4 0.3 41 No RRPMs 2 3 187 428 234 402 −20.3 6.4 42 No RRPMs 39 40 160 212 190 209 −15.5 1.6 43 No RRPMs 2 3 185 431 234 402 −20.9 7.1

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CHAPTER 3: SUMMARY OF FINDINGS

This testing was designed to evaluate the accuracy of the RetroTek-MU mobile pavement marking retroreflectometer across a range of factors. These factors are typically encountered during data collection and their impact needs to be minimized to have a system that can continually collect accurate retroreflectivity data across a range of pavement markings in various conditions. The testing included 42 tests on 91 pavement marking segments over a variety of road segments to evaluate the mobile retroreflectometers performance. The open road testing evaluated typical road surfaces and pavement markings in typical data collection conditions. Overall the retroreflectivity trend along the test sections was consistent between the RetroTek-MU and the portable retroreflectometer with an R2 value of 0.9417. The average systematic error was −5.7 percent with an average random error of 8.7 percent. The results indicate that when considering marking color or marking pattern the error was approximately 11 percent or less. The measurements at the left or right in-lane positions differed by approximately 10 percent or less when compared to the center of the lane position. The low RL calibration level resulted in data that were between 6 and 9 percent lower on average than data collected with the high RL calibration setting. The closed course testing results indicated that the majority of the mobile data were within 10 percent of the portable data. The average systematic error was 0.9 percent, with an average random error of 5.7 percent. Overall the retroreflectivity trend along the test sections was consistent between the RetroTek-MU, and the portable retroreflectometer with an R2 value of 0.9878. The mobile and portable data closely matched each other with almost no bias as the line of equality and data trend line were nearly on top of each other. The average error was less than 7 percent for any subset of color or marking pattern. The difference between the measurements with and without the RRPMS was less than 3 percent different on average. The testing and results described in this report provide quantitative information as to the accuracy of data collected with the RetroTek-MU mobile pavement marking retroreflectometer across a range of factors.

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APPENDIX: IMAGES OF TEST AREAS

Figure 4. Villa Maria Test Area.

Figure 5. Jones Road Test Area.

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Figure 6. Leonard Road Test Area.

Figure 7. State Highway 47 Test Area.

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Figure 8. Farm to Market 60 Test Area.

Figure 9. Closed Course Test Area Marking Examples Part I.

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Figure 10. Closed Course Test Area Marking Examples Part II.

Figure 11. Structured Marking Test Area.

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Figure 12. Preformed Tape Pavement Marking Test Area.

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