Yellow Thermoplastic Road Markings with High Retroreflectivity: Demonstration Study in Texas

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جزئیات بیشتر

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۲۰۲۱

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scopus – master journals – JCR

ایمپکت فاکتور

۴٫۲۷۶ در سال ۲۰۲۰

شاخص H_index

۲۶ در سال ۲۰۲۱

شاخص SJR

۰٫۹۰۱ در سال ۲۰۲۰

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Q1 در سال ۲۰۲۰

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توضیحات مختصر محصول
Yellow Thermoplastic Road Markings with High Retroreflectivity: Demonstration Study in Texas

فهرست مطالب مقاله:

Abstract

 

Road markings are a niche category of industrial coatings with requirements related to both the coating itself and the layer of glass beads on top of it that furnish retroreflectivity (RL) – their key property, particularly needed during driving at night time and in rainy weather conditions. The most frequently used glass beads, with refractive index 1.5, are capable of delivering RL reaching only about 400 mcd/m²/lx in white and 200 mcd/m²/lx in yellow markings; very low retroreflectivity under wet conditions, seldom exceeding 50 mcd/m²/lx can be obtained. Re- cently introduced ‘premium’ glass beads, with refractive index marginally increased, to 1.6-

1.7, can yield more than twice as high RL. It was envisaged that high RL in a yellow road mark- ing could be achieved if it were to be applied in form of a structure with high vertical profile reflectorised with these premium glass beads. Because of strict compositional requirements for road markings used in North America, a demonstration trial was made possible due to a special specification that allowed some departure from the fixed standards, but within new high-level demands related to RL under both dry and wet conditions. The tested material was a thermo- plastic mass applied as regular dots that due to round surface would facilitate rainwater drain- age, thus permitting the glass beads surface to be exposed to deliver RL under wet conditions. The performance achieved in the field was excellent: RL  ۸۹۴ mcd/m²/lx under dry and 160 mcd/m²/lx under wet conditions were achieved. Moreover, the applied road marking system maintained the required performance for 12 months (RL 774 mcd/m²/lx), while the control failed (RL<100 mcd/m²/lx). The outcome of this demonstration is expanding the knowledge related to this specific type of industrial maintenance coatings and should be of profound interest to road administrators who are searching for improved performance of road marking materials to in- crease road safety, particularly on major thoroughfares.

 

Keywords: Thermoplastic road markings; glass beads; retroreflectivity; structured road mark- ings; durability; road safety.

 

 

  1. Introduction

In the European Union countries in 2019 there were 22,800 road fatalities (23% decrease from 2010), while in the United States 38,800 people lost their life on roads (11% increase as compared to 2010). Such human losses cause enormous social and economic costs, which were estimated at reaching even 3% of World’s Gross Domestic Product (World Health Organisa- tion, 2015). It was calculated that one road accident in the European Union was costing the economy between 0.7 and 3.0 million euro, depending on the country (Wijnen et al., 2019). In the United States, the expenses per occurrence were estimated at 334,000 dollars (USD) in 1988 (Elvik, 2000); the total expense for 2005 was estimated at 9.9×۱۰۱۰  USD without including several direct and indirect costs (Naumann et al., 2010). Surprisingly, no updated estimates forNorth American data are available in peer-reviewed literature.

Driving control is based mostly on visual input. Visibility of the road ahead at night requires external lighting in form of vehicle’s headlights and/or street lamps and/or other external light sources. While installation of street lighting was reported to reduce night time accidents by even 50% (Wanvik, 2009), it is not a reasonable option in rural areas due to excessive costs. Major findings related to the issue of drivers’ visual performance under various illumination condi-tions were recently reviewed and their discussion is beyond the scope of this article (Brémond,

2020). Importantly, a study has shown that visibility level, rather than illumination level, was better correlated with driving performance (Brémond et al., 2013). Visibility of road markings, defined through ‘equivalent disc’, was recently assessed through a laboratory psychovisual ex- periment: it revealed a good match of theoretical calculations with experimental data for the disc diameters above 0.1° (at illumination of 1 cd/m² calculated was road markings preview distance of 56-86 m, depending on their configuration, with larger values obtained for wider and longer lines), but for disk diameters below 0.1° the models failed (Crescenzo et al., 2019). Road markings (including alternate solution like lighted road studs), which delineate the path ahead and thus make it visible, meaningfully contribute to lane keeping by all drivers (Horberry et al., 2006; Shahar et al., 2016).Whereas there is a plethora of articles related to road construction materials and road safety, performance of horizontal road markings is relatively infrequently addressed by them. None- theless, this niche yet ubiquitous category of construction materials with very specific require- ments, is inexpensive and effective (Miller, 1992). Performance standards for road markings in North America were set many years ago and were not really updated to remain current with the modern technologies: as an example one could give the specification related to glass beads, TT- B-1325 (General Services Administration, 2007), which still does not recognise that their re- fractive index (RI) could be between 1.55 and 1.90, exactly like it did not in the prior version, from 1993. 

 

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