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ISSN 0347-6049

nde _V/I/meddel

517A 1989

A study of different types of road markings

as related to retro - reflectivity and wear Sven - Olof Lundkvist

w Vay- och Trafik- Statens vag- och trafikinstitut (VTI) * 581 01 Linkoping INSUHUIUITOL swedish Road and Traffic Research Institute * $-581 01 LinkGping Sweden

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E

ISSIV 0347-6049

V meddelan de

M

577A

7989

A study of different types of road markings

as related to retro - re ectivity and wear

Sven - Olaf Lundkvist

T. Vgg' Statens veg- och trafiklnstitut / VT!) 0 58 7 07 Linkdping

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Preface

This study was defrayed by Cleanosol AB and the Swedish Road and Traffic Research Institute.

Cleanosol was responsible for the different materials and their application,

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Contents

ABSTRACT, . . a a a a a a a a a a a a . a a a a a a . a a a , a . . . a a a . . a a. v

1 INTRODUCTION a a . a . . a a a a a a a . . a . . . a a . . . a . a a . a . '. 1

2 OBJECTIVE . , . a a . a a a a . . . a . a g a a . . . , . . . . , a a . . 1

3 TEST PLAN . . . a . . a a a o a a a . a . a . . . , . . . a a , . a 1

3.1 Varying additions of glass and plastics beads . . . a o . . . 1

3.2 Bead make . . . , . . . a . . . a . . . o a n . . . o . . . 1

303 Bead size . . . a . . . . t . . . a . a . a a a . . . .. 2

3.4 Description of all the compounds , . a a . . . 2

4 MEASURING METHOD . a a . . . a a . . . a . . . a . . . . 3

4.2 Notations. .. . . , a . . . a . o . . . a . . . .. . 3

5 RESULTS . . . a a . . . a . . . a . a . . . 3

501 Varying additions of glass and plastics beads . . . 3

5.2 Bead make . . . a n . . . o . . . '. . . 4

5.3 Bead size . . . o . . . 5

5.4 Measurements using LTL-BOO . . . . a . . . 6

6 DISCUSSON . . . . a . . . 7

6.1 Varying additions of glass/plastics beads . . . 7

6.2 Bead make . . . 7

6.3 Bead size . . . 8

7 CONCLUSIONS . . . 8

REFERENCES . . . 8

APPENDIX A . . . .' . . . 9

A1. Effect of varying additions of glass/plastics beads . . . 9

A20 Effect of bead make . . . 10

A3. Effect of bead size . . . 12

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ABSTRACT

During a period of two years the specific luminance and durability of thermoplastic road marking materials have been studied, The contents of 18 different compounds have been varied systematically as to

a) the proportion of reflective glass and plastics beads, b) the make of the glass beads,

c) the size of the glass beads.

According to the results addition of 20% by weight of glass beads and 5% by volume of plastics beads is suitable for roads with no fixed lighting.

On roads with fixed lighting, on the other hand, the durability should be considered as more important than the specific luminance, A suitable addition of glass and plastics beads is 10% by weight and 5% by volume, respectively.

Furthermore, the study showed that gass beads in a thermoplastic compound should be of a size range of more than 100 um and that the specific luminance of the beads made by Potter is much higher than of beads manufactured in East Germany.

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1 INTRODUCTION

In an earlier field investigation 12 different compounds were studied with regard to retroc reflectivity and wear (Ref. 1).

Briefly this investigation showed:

Q

A suitable addition of pre-mix beads is around 20% by weight.

Drop-on beads add to the retro-reflectivity just after application. After one winter no effect (negative or positive) of these remains.

No positive effects could be found from the admixture of small beads into the com-pound, for compounds containing up to 30% by weight of pre-mix beads.

Admixture of plastics beads instead of glass beads into the compound resulted in good durability but poor retro-reflectivity.

The above results have in parts been used as a basis for the new investigation.

2 OBJECTIVE

Utilising the previous findings the objective of this investigation has been to study retroe reflectivity (specific luminance) and wear wth regard to:

1) Varying additions of glass and plastics beads. 2) Two different makes of beads.

3) Different bead sizes (glass beads).

3 TEST PLAN

The investigation has been designed as a field test based on the model used earlier (Ref. 1). As indicated above differentiation can be made between three separate sections of the investigation.

3.1 Varying additions of glass and plastics beads

Three different additions of glass beads have been combined with three different addi-tions of plastics beads as shown in Table 1.

Table 1. Plan of first test section

I l [plastics | |% by volume 5 10 15 l

r

i

i

lglass

I

|

|% by weight] I |10 | x x x | I15 | x x x | | x x x | l . 1

I20

I

Thus this test section covered nine different compounds. 3.2 Bead make

Potters glass beads have been compared with beads of East German manufacture. This was done for the size fractions 50-100, 100-500 and 300-500 um.

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3.3 Bead size

Six different size ranges of beads were tested, viz.: 50-400, 100-200, 100500, 300500,

0-850 and 200-850 um.

3.4 Description of all the compounds

Table 2 shows particulars for all the compounds tested in the investigation while Table 3 shows those covered by the test sections.

Table 2. Description of the compounds covered by the investigation.

I I

[compound % by % by size make |

| weight volume range I

| glass plastiCS' (um) (P=Potters) |

I (OsEast German) | l l I I

IA

10

5

o~850

o

|

[B 10 10 o~850 o I la 10 15 0-850 0 | ID 15 5 0-850 0 | IE 15 10 0-850 0 | IE 15 15 0 850 0 I Is 20 5 O=850 o |

IH

20

10

0-850

0

|

|1 20 15 0 850 0 | |J 20 a 50-100 0 |

[K

20

-

50 100

P

|

IL

20

-

100 500

0

|

IM 20 - 100 500 P |

IN

20

a

300 500

0

|

|o

20

-

300 500

P

|

IP

20

~

100-200

0

|

IQ

20

-

o~850

o

|

IR

20

-

200-850

0

|

I I

Table 3. Compounds covered by the three test sections

compounds included I I test section II _ _ _ -I ll glass/plastics A B C D E F G H I |2 head size J L N P Q R JKLMNO I3 bead make I

Note that compounds J, L, and N have been included in both test sections 2 and 3.

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4 MEASURING METHOD

A description and discussion of measurement of the specific luminance using the Erichsen reflectometer are given in an earlier report (Ref. 1). During the spring of 1985 (the last measurement date) the measurements were carried out using both Erichsen and a new instrument -- LTL-800. The later has the advantage of simulating a realistic observation and illumination distance, Le. 50 m. The instruments are compared in Table 4.

Table 4. Comparison between Erichsen and LTL-800 reflectometers

l l

IInstru- Observa Illwmina~ Simulated I

Iment tion tion observation |

I angle angle and illumination I

I distance I

l l

I l

IErichsen 5.0° 3.5° approx. 12 m |

ILTL 800 1.37° O.74° approx. 50 m I

l l

4.2 Notations

In the section detailing results the following notations are used:

Notation refers to unit

SL6 mean value of specific luminance (mcd/m2)/qu at measurement date i

S. standard deviation for SL. (mod/m2)/lux

SI...x mean value of specific luminance

for the lines remaining intact (mcd/m2)/lux on the third measurement date

B proportion of markings wom away by the last measurement date

5 RESULTS

Below "SL." means the specific luminance at measurement date i, where i is defined as:

measurement occasion 1 date 1984-05-08 measurement occasion 2 date 1984-08-28 measurement occasion 3 date 1985-05-29

5.1 Varying additions of glass and plastics beads

Previous investigations have shown that the specific luminance depends on the amount of

glass and plastics beads added. It was also found that the durability was good for compounds containing plastics beads. This test section aims at establishing the optimum additions of glass and plastics beads with respect to specific luminance and durability. Table 5 shows the specific luminance over three measurement dates while Table 6 shows the specific luminance and durability after two winters.

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Table 5. SL as a function of the content of glass and plastics beads over a two-year 142 178 88 pe od I I l [Compound I SLO SL1 SL2 I I l I I I I I A I 101 119 103 | | B I 107 133 94 I | c I 115 144 91 I I D I 122 143 88 I I E I 124 142 86 I I F | 125 159 74 I | G I 130 157 97 I I H I 145 167 78 I

l I

l

|

I I I

Table 6. Specific luminance and durability after two winters

I l l [Compound I SL2 32 SLx B I l l l | I l | A I 103 31.7 114 0.04 I | B I 94 45.2 122 0.21 | | c I 91 50.6 133 0.31 | I D I 88 60.9 145 0.42 I I E I 86 56.1 139 0.40 I I F I 74 60.9 163 0.56 I I G | 97 64.7 164 0.40 I I H I 78 69.2 169 0.54 I I I I 88 76.1 192 0.58 I l l l

As in earlier investigations the proportion of glass beads has been found to in uence the specific luminance -- the more beads, the higher the SL value. This applies to the whole 2-year period during which measurements were made. But the amount of plastics beads has only had an effect on the specific luminance during the first two measurement dates, after one winter. After a further winter the effect of plastics beads had disappeared. The above means that compound I exhibited the best reflectivity characteristics - but also the poorest durability. Compound A was the most durable.

Compound G has been found the most interesting. Because of reasonably good durability its SL2 is high. SLx which shows the specific luminance of an intact line is also high 164 (mcd/m2)/lux. Variance analysis and comments are given in appendix A. 5.2 Bead make

For three different size ranges of glass beads two makes were studied Potters and

beads from an East German firm. The results are shown in Table 7 and 8.

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1M-

SL as a function of bead make and size range over a 2-year period

I r I l

|Size range I Potters | East Genman I |(um) | SLO SL1 SL2 | SL0 SL1 SL2 | l I I I I I I I | 50-100 | 96 102 57 | 100 106 72 | | 100-500 | 159 180 100 | 130 145 85 | | 300 500 | 157 198 102 | 122 145 75 | I I I I

Table 8. Specific luminance and durability after two winters

I I I I

ISize range I Potters I East German |

|(um) | SL2 32 SLx s | SL2 32 SLx s | l I l I I I I I | 50-100 | 57 37.3 105 0.54 | 72 36.6 105 0.35 | | 100-500 | 100 79.7 189 0.46 | 85 59.9 143 0.46 | | 300 500 | 100 84.5 173 0.48 | 75 57.7 134 0.50 | I I I I

It is clear from Tables 7 and 8 that for compounds containing large beads (up to 500 um) Potters have worked better than the East German. For small beads (up to 100 pm) the opposite applies. However, variance analysis has shown that this latter difference is not signi cant (p<.01). Thus this test section only enables the conclusion that Potters beads perform better than the East German for size ranges 100-500 um and 300-500 pm. It is also clear that small beads have not functioned as well as large beads. This will be dealt with in section 5.3

Variance analysis and comments are given in appendix A. 5.3 Bead size

The importance of bead size for the specific luminance has been investigated using five different size ranges. The results are shown in Tables 9 and 10.

Table 9. I

[Size range SLO SL1 SL2 I|

I (turn) I

l

4

| 50 100 100 106 72 | | 100-500 130 145 85 | | 300-500 120 145 75 | | 100-200 114 146 98 I | 0-850 112 144 71 l | 200-850 118 155 68 I l I

SL as a function of size range over a 2-year period

(11)

Table 10.. Specific luminance and durability after two winters l ISiZe range SL2 32 SLx B |

llum)

l

l

l

| 50~100 72 3646 105 0935 | | 100=500 85 59.9 143 0046 | | 300w500 75 5707 134 0050 | | 100~200 98 5705 144 0.31 | | 0~850 71 54.6 143 0.42 | | 200 850 68 54.7 140 0.54 | l I

This test section has shown that the compound containing small beads (50-100 pm) had lower specific luminance than the others at the first two measurement dates. Viewed over the whole measurement period no other compound looks different from the rest. Variance analysis and comments are given in appendix A.

5.4 Measurements using LTL-BOO

During the third measurement date the measurements were simultaneously made with the Erichsen reflectometer and an instrument of type LTL-BOO. The latter employs obser-vation and illumination angles of 137° and 0.74°, respectively, which simulates an ap-proximate distance on the road of 50 m. This has to be compared with the geometry for Erichsen of 500° and 3.5", respectively, which corresponds to about 12 m as the observa-tion and illuminaobserva-tion distance, SL2 and SLx for the two instruments are compared in Table

114

Table 11., Comparison of reflectometers of types Erichsen and LTL-8OO

l l

[Compound Erichsen LTL-8OO I

| SL2 SLx SL2 SLx | l l l l | A 103 114 67 76 | | B 94 _ 122 58 82 | | c 91 133 59 91 | | D 88 145 65 114 | | E 86 139 57 96 | | F 74 163 46 117 | | G 97 164 73 131 | l H 78 169 61 135 | l I 88 192 62 153 l | J 71 105 35 53 | | K 57 105 30 55 | | L 85 143 61 114 | | M 100 189 88 181 | l N 74 134 55 110 | | o 102 173 100 195 | | P 98 144 60 90 | | Q 71 142 55 121 | | R 68 140 54 141 | l l

(12)

We can detect some differences between the Erichsen and LTL-800 measurements. Primarily the level of SL, as measured with LTL 800, is lower than that obtained with Erichsen. Some compounds appear to have been under-evaluated by Erichsen, other have been over-evaluated. On the whole it can be said that the conclusions that could be drawn from the Erichsen measurements are likely to have applied even if LTL-800 had been used over the whole 2-year period. However, the variance analysis for the third set of measurements has in one case given different results for the two instruments; namely that still after two years compounds containing small beads (50-100 urn) are inferior to compounds containing large beads. This was the only effect which could not be demon-strated with the Erichsen instrument. The other way about, it has not been possible to detect an effect with the Erichsen instrument that was not detected with LTL-800.

The correlation between SL-values measured with the two instruments was: SL(Erichsen) = 24 + 1.0 SL(LTL-800)

However, the regression coefficient varied depending on the type of compound. Thus for

compound J: '

SL(Erichsen) = 4 + 1.9 SL (LTL-800) while for compound Fl:

SL(Erichsen) = 21 + 0.9 SL(LTL-=800).

This leads to the conclusion that it is impossible to translate values measured with one of the instruments to the other without knowledge of the composition of the compound.

6 DISCUSSION

6.1 Varying additions of glass/plastics beads

Previous tests (Ref. 1) have shown that compounds containing plastics beads are more wear resistant than glass beads. In this investigation glass beads and plastics beads were mixed. A comparison of compound 0 (20% glass beads, 0-850 um) with compound G (20% glass, 5% plastics beads, 0-850 um) reveals no difference with regard to durability but compound G exhibits higher specific luminance. Variance analysis has shown that the specific luminance increases with both the content of glass beads and plastics beads. As the compounds are worn down the effect fades away and after two winters no significant effect could be established.

Compounds A C (10% glass beads) may be said to have a somewhat too low initial value. However, compound A should be perfect for built-up areas where there is fixed lighting - the compound has very good wear resistance and exhibits a specific lumi-nance that satisfies the requirements of BYA.

Compounds D-F may be said to represent an intermediate group, exhibiting neither exceptionally good durability nor high specific luminance.

Compounds G-l contain 20% glass beads. Of these G appears better than H and l. Admittedly the SL value for intact marking (SLX) is lower but its durability is better than for the other two. Without taking cost aspects into consideration it could be said that com-pound G seems the most suitable for a road without fixed lighting.

6.2 Bead make

This test section has shown that beads from Potters give a higher specific luminance than the East German beads within size ranges 100-500 and 300-500 pm. The compounds with beads in size range 50-100 um have exhibited low specific luminance for both bead makes and must be regarded as of Iitte interest.

(13)

6.3 Bead size

Of the six size ranges tested compound J (50-100 um) was found to be inferior to the others at the first two measurement dates. However, after two winters, on the third measurement date no significant difference could be detected between the different com-pounds. But note that compound J was shown to be inferior over the whole twoayear period when measurements were made with LTL 800.

The results during the first year after application are somewhat contradictory; at the first measurement date compound L (100°500 um) was better than the rest, while at the second measurement date compound R was better than the rest. But the differences are not dramatic, and the main conclusion to be drawn is that over the whole two-year period the compound with the small beads has been inferior as compared with the rest.

7 CONCLUSIONS

In general it can be said that for a compound to exhibit high specific luminance it should contain beads larger than 100 um and that Potters beads are to be preferred over East German. As shown by earlier investigations it was now also found that increasing the content of glass beads leads to improved specific luminance. Previously it was also established that the optimum is around 20% of glass beads -- if the content is raised further, durability deteriorates. This new investigation has shown that in addition to the 20% of glass beads, 5% of plastics beads can be added without an adverse effect on durability, but with improvement in specific luminance. The bead size is not critical as long as the compound contains beads larger than 100 um. Compounds containing solely beads smaller than 100 um have exhibited good durability but low specific luminance. For the size ranges of interest Potters beads have performed better than East German beads.

The conclusions drawn from the three sections of this investigation can be summarised as follows:

- A compound containing 10% of glass beads and 5% of plastics beads is very durable but has only moderate specific luminance - may be suitable for a road with fixed

gh ng.

- A compound containing 20% glass beads and 5% plastics. beads exhibits high specific luminance and acceptable durability. The plastics beads have raised SL without re-ducing durability.

- Compounds containing Potters beads have exhibited higher specific luminance than compounds with East German beads. This applies to bead size in the range larger than 100 um.

- Compounds containing solely small beads (<100 um) have low specific luminance.

REFERENCES

1 Retro-reflective characteristics of road markings, S-O Lundkvist, WI 1986.

(14)

APPENDIX A

DESCRIPTION OF AND COMMENTS ON VARIANCE ANALYSIS

The following notations are used below:

Effect A variable or interaction between several tested variables.

F F-quotent shows if a tested variable has had a Significant effect. Significance level.

(02 Proportion of total variance that can be explained by a certain effect. df Degrees of freedom.

The aim has been to test in the investigation the effects at significance level p<0.01. This means that the risk of regarding an effect as significant, although this in reality is not decisive for the test, is 1%.

A1. Effect of varying additions of glass/plastics beads

Table A1. Variance analysis of SL as a function of the content of glass and plastics beads and the measurement date

F I

IEffect Significance I

| df F (P<0.01) m2 |

I I

I I

Iglass beads (A) 2 19.4 yes 0.03 I

Iplastics beads (B) 2 1.89 no 0 I

Imeasurement date (C) 2 166.64 yes 0.31 |

|AxB 4 0 . 23 no 0 | IAxC 4 9.61 yes 0.03 | |BxC 4 4.20 yes 0.01 I IAxBxC 8 0 . 41 no 0 | I I Comments:

Viewed over the whole two-year period SL has depended on the content of glass beads (A) and the measurement date (C). The interaction effects AxC and BxC are also significant, which means that variance analysis should be done separately for the three different measurement dates. This is detailed in Tables A2-A4.

Table A2. Variance analysis for measurement date 1 with regard to variation in SL with glass and (plastics) bead content.

I .

IEffect Significance I

I

| df F (P<0.01) m2 |

'L

l

Iglass beads (A) 2 263.99 yes 0.67 |

Iplastics beads (B) 2 21.01 yes 0.05 I

leB 4 2.05 no 0.01 |

I

(15)

Table A3. Variance analysis for measurement date 2 with regard to variation in SL with glass and (plastics) bead content.

I I

IEffect Significance I

I df F (P<0.0l) m2 |

l J

I l

Iglass beads (A) 2 265.83 yes 0.56 I

Iplastics beads (B) 2 92.16 yes 0.19 I

l

l

IAxB 4 4.26 yes 0.01

l

Table A4. Variance analysis for measurement date 3 with regard to variation in SL with glass and plastics bead.

I I

IEffect Significance I

| df F (P<0.01) m2 |

I I

I I

Iglass beads (A) 2 0.95 no 0 I

[plastics beads (B) 2 0.86 no 0 I

l

I

IAxB 4 0.22 no 0

l

Comments Tables A2-A4 indicate significant effects of both glass and plastics beads

on the first two measurement dates. However, at the third measurement

date all the effects have disappeared and the variations in SL can entirely

be attributed to variation in wear and random errors.

A2. Effect of bead make

Table A5. Variance analysis for SL as a function of bead make, bead size and measurement date. 0.26 no I I IEffect Significance I | df F (P<0.01) m2 | I I I I

Ibead make (A) 1 28.51 yes 0.03 I

[bead size (B) 2 69.67 yes 0.16 |

[measurement date (C) 2 116.99 yes 0.27 I

IAxB 2 14.91 yes 0.03 | IAxC 2 2.25 no 0 | IBxC 4 4.59 yes 0.02 I 4 0 | I IAxBxC I

Comments. The main effects are here significant, nevertheless (02 indicates a weak effect of bead make. The interesting significant interaction effect is between make and size (AxB). It shows that SL has varied with bead make, but differently for different size ranges. Separate analysis for this is given in Tables A6-A8.

(16)

Table A6. Variance analysis for size range 50-100 um with regard to variation in SL with bead make and measurement data,

I I

IEffect Significance I

| df F (P<0.01) w2 |

l l

I I

Ibead make (A) 1 4.01 no 0001 |

[measurement date (B) 2 43°49 yes 0037 |

I

I

leB 2 0°72 no 0

I

Table A7. Variance analysis for size range 100 500 pm with regard to variation in SL with bead make and measurement date.

I I

IEffect Significance I

| df F (P<0.0l) m2 |

I I

I I

lbead make (A) 1 14.33 yes 0 06 I

Imeasurement date (B) 2 37°56 yes 0.32 |

|AxB 2 0., 72 no 0 |

I in

Table A8. Variance analysis for size range 300=500 um with regard to variation in SL with bead make and measurement date.

I I

IEffect Significance |

| df F (P<0.0l) o2 |

l I

I I

Ibead make (A) 1 28.35 yes 0.10 |

Imeasurement date (B) 2 45°79 yes 0934 |

!

|AxB 2 1.12 no 0

l

Comments: For size ranges larger than 100 pm the effect of bead make has been significant, i.e. Potters beads have given higher specific luminance than the East German No effect could be demonstrated for the smaller size range.

(17)

A3. Effect of bead size

Table A9. Variance analysis for SL as a function of bead size and measurement date.

I l

IEffect Significance I

| df F (P<0.0l) m2 |

I I

I I

Ibead size (A) 5 7.12 yes 0.04 I

Imeasurement date (B) 2 137.65 yes 0.36 I

10 2.53 yes 0.02 I

l

IAxB

I

Comments: Significant main effects show that SL has varied with bead size range and measurement date. The interaction points at the effect of bead size having been different at the two measurement dates. Separate t-tests (p<0.01) haVe therefore been made, the following significant differences then being obtained as detailed in Tabel A 10.

Table A10.

three measurement dates.

t-test (p<0.01) for difference in SL for different bead size ranges on the

I l

Imeasurement date size range better than I

I I I I I1 50-100 um - | I 100 500 um 50-100, 100-200, 0-850, 200-850 um I | 300-500 um 50 100, 0-850 pm | | 100-200 um 50-100 pm I I 0-850 um 50~100 um I I 200*850 pm 50-100 um, I I I l I I2 50-100 pm. - I

|

100-500 pm

50-100 pm

|

|

300-500 um

50-100 pm

|

| 100 200 um 50-100 um I

|

0-850 um

50-100 pm

|

| 200-850 um. 50-100 um, 300-500 um I I I l I I3 No significant differences I I I

Comments: The compound containing beads in size range 50-100 um performed worse than the others on the first two measurement dates. In addition, on the first measurement date size range 300 500 um was better than 0-850 um and on the second measurement date the size range 200-850 urn was better

than 300-500 um.

(18)

Figure

Table 1. Plan of first test section
Table 3. Compounds covered by the three test sections
Table 4. Comparison between Erichsen and LTL-800 reflectometers
Table 6. Specific luminance and durability after two winters
+7

References

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