NOW let us turn our attention to yet another functional paint called Road Marking Paints. Earlier road contractors used to mark the roads viz: the central median, side boundaries and lane separating lines with ordinary synthetic enamel white. According to the state of Michigan, the idea of using a painted centre line was conceived in 1911 by Edward N. Hines, the chairman of the Wayne County, Michigan, Board of Roads, after watching a leaky milk wagon leave a white trail along a road. White Lines painted on the pavement indicate traffic travelling in your direction. Broken White Line: you may change lanes if it is safe to do so. Solid White Line: requires you to stay within the lane and also marks the shoulder of the roadway. Yellow Lines mark the centre of a two-way road used for two-way traffic. This had a very short life in view of heavy vehicular traffic on the roads. Frequent road markings added to the road maintenance costs. Slowly they shifted to water based coatings with good white pigments such as Rutile and higher percentage of Emulsions to give better scrub resistance so that the coating can last longer. They were also used in factory floors as markers or indicators and cautionary signals to guide the people working in the Factory, Airport taxiways, Apron etc.
Types of Road Paints: Water Based Road Paints - paint specifically designed for paved surfaces. It is bright, highly visible and ideally used in parking lots and other light traffic areas. Glass beads can be added for extra reflectivity. No doubt these coatings proved better than synthetic enamels, but still they too proved not a very effective coating to withstand traffic pattern, especially in the highways. Research and Development came out with a better product known as Thermoplastic Road Marking Paints. Also asphalt is an oil-based surface is ill-suited for paint adhesion. If one attempts to paint the asphalt driveway with conventional paints, soon will end up with paint failure
Thermoplastic Road Marking Paint, also called hot melt marking paint, is a kind of powder paint. When applied as road surface markings, a hot melt kettle is used to heat it to 200 °C , after which it is sprayed on the road surface. The coating then becomes a line after cooling. This paint is thick coating, wear-resisting, bright and reflective. In recent years, practical applications have proved that the marking lines lack certain surface roughness and can easily cause wheel slip, resulting in a traffic accident in snow and rainy weather. Therefore, some countries once restricted the use of this paint. In order to increase the antiskid performance of the line, thermoplastic paint has added reflective glass beads. Thermoplastic can be used very effectively for large anti-skid areas on roads and pedestrian walkways by adding glass beads. It can be produced in any colour and is great for car parks, factory walkways and many other areas. It's fast drying and can be driven over after just a few minutes.
Thermoplastic marking paint is mainly composed of synthetic resin, glass beads, pigments, packing materials, additives, etc.
- Synthetic resin has thermoplasticity, make the hot melt coating fast dry and strong adhesive to the road surface.
- Additives in the paint can increase the plasticity of the coating, and make it resistant to subsidence, pollution and colour fading.
- Pigments: the common colours of road lines are yellow and white. White pigments are mainly titanium dioxide and zinc oxide, while yellow pigment is mainly heat-resistant yellow lead.
- Packing materials, as filling added into the paint, ensure mechanical strength, wear resistance, and colour of paint coating. The particle size will affect liquidity and precipitation, as well as the surface processing.
- Glass beads are added in order to improve the identification of lines at night, to improve the brightness and durability of the marking. Glass bead is colourless and transparent ball, has function of light refraction, focusing and directional reflection. Glass bead mixed in the coating or dispensed throughout the coating surface can reflect car light back to the driver's eyes, thus greatly improving the marking visibility.
Various road marking paints
Acrylic resin based road marking paints: Properties
Surface: Asphalt and concrete Machine: Airless or Pneumatic machine, brush, roll 2 Wet Paint Consumption Amount: 500g/m 2 Glass Bead Consumption Amount: 300g/m. Thinning: It is used without thinning. Temperature: Between 5 °C and 40 °C Maximum Humidity: 80% Dry Time: 2 min. (air temperature 17 °C, surface temperature 22 °C, 49% humidity, 6 km/h wind) Illumination Factor: LF7 / β ≥ 0.85 Viscosity: 80-95 KU Density: 1.58 g / ml ± 0.05 Solid Matter Rate: 76% ± 2\.
Machine application technique of road marking paint An indepth analysis of water based road marking paints
An indepth analysis of water based road marking paints
Horizontal road markings are one of the essential safety features of modern roadways. All of the utilised systems consist of a pigmented coating containing partially embedded retro reflective elements such as glass beads. In addition to durability and functionality of the road marking, ease of application and effect on human health and environment are primary considerations for their selection. Road marking systems can be divided into plural component materials that cure due to chemical reaction occurring at the site of application, thermoplastics that require heat for application, and paints, drying upon evaporation of the dissolving medium. Over 100 years old solvent borne technology furnishes paints that afford consistent application properties under a variety of conditions such as lower temperatures and high humidity. Their environmental and human health impact is significant and durability quite poor. Modern waterborne paints are based on acrylic resins and incorporate developed in the 1990s quick-set chemical mechanism for drying. Under favourable weather conditions, they dry faster as compared to solvent borne. However, their known weakness is risk of washout in case of rain and sluggish development of washout resistance at marginal application conditions like high humidity and low temperature. Impact of waterborne paints on human health and environment is very significantly minimised as compared to other materials. Their durability is significantly higher as compared to solvent based paints.
Horizontal road markings are one of the safety features on modern roads; their influence on driving safety is especially prominent at night and in adverse weather conditions. The markings can be defined as a set of longitudinal and transversal lines, signs and symbols on the surface of transportation infrastructure. They represent a fraction of overall traffic signalisation and cannot be at present replaced by other means. Studies show that generally, the presence of only centre and edge lines can reduce all accidents by 20%. Efficiency and durability of road markings are required by both road users and the road authorities. From the users' point of view, road markings provide an optical path by means of contrast of colour and luminance with the road surface and it appears that these properties should be maximised. Selection of the type of road marking materials by road administrators depends on many factors, including the desired durability, required visibility, price, and local considerations. Considerable funds are allocated to keep the markings at adequate performance level. Even though the overall long-term performance and cost should be balanced, unfortunately, quite frequently it seems that short-term expense plays more significant role. A model could be functional contracts, such as are in place for example in Finland (as an example) where the application company is paid for maintaining the retro reflectivity and the choice of materials is in its hands. Environmental friendliness is also critical: not only in terms of contents of emissions of Volatile Organic Compounds (VOC), but also as an overall impact on our planet.
Assessment of effects of various road markings has not produced definitive results as to which road markings maximise safety benefit. Field of driver attention is changing depending on the construction characteristics of the road, the traffic conditions, and the vehicle speed, generally decreasing with increase if the speed and increasing when reducing speed. Studies showed that with high visibility markings on outer roads the drivers tend to increase speed, thus nullifying the benefits on safety. At urban level, things get more complicated because of factors like pedestrian crossings, turnabouts, stop signals and also a different way of driving. It was also demonstrated that removal of all horizontal markings in low-speed residential areas in a “shared space” concept lead to increased safety for all due to drivers paying more attention on surroundings and other road users instead of following the guiding path.
The role of road markings
Road markings are one of the most important components of traffic signalisation because of their position in the central area of drivers' attention. Their function is to warn drivers about conditions of the road and its construction characteristics and to help in determining lateral or transverse position of their and other vehicles. Important feature of road markings is their continuity along the entire length of the road, which is a significant fact in the process of orientation. It can be said that road markings are telling the driver, with a specific language, what to do and how to behave in certain situations in traffic. They are especially beneficial in poor visibility conditions. The main tasks of road markings are:
- Drawing attention to the situation around and in the area in front of the vehicle, which requires special attention and caution.
- Ensuring traffic management, particularly at approaches to intersections.
- Defining the road in its course and layout.
- Giving drivers clear orientation and safe guidance by day and night.
- Informing drivers about certain legal restrictions.
- Helping to regulate traffic flow in an optimal way.
- Helping drivers to safely reach their destinations.
Two important factors describe connection between driver and road markings:
A driver must be able to see road markings at a certain distance to perceive, process, and react to the information that the pavement marking presents in order to receive adequate information to safely guide the vehicle. Since the required distance increases as the speed of the vehicle increases, it is often described as constant preview time.
“It has been established that for night time low-beam conditions, a driver requires a minimum recommended preview time (comprising both eye fixation time and driver reaction time) of 3.65 seconds at 80 km/h, of oncoming road geometry to enable safe negotiation without the driver requiring to shift attention away from the road, to look for other clues.“
The contrast between white (in some countries also yellow) marking and black road surface is sufficient at daylight, but at night retro reflectivity plays more significant role. Visibility of road markings at night is accomplished by materials like glass or ceramic beads, which reflect the light from vehicles headlights.
Poor visibility of most markings at night during rainy conditions is caused by water blocking retro reflection. This deficiency can be alleviated by utilisation of structured markings and large glass beads, which do not become submerged during normal rain conditions. Retro reflectivity is achieved as long as the reflective elements remain properly embedded – upon their loss or imperfect embedment, only daytime reflectivity is maintained.
Retro reflectivity is better if the driver is sitting lower, because the observation angle is smaller, as demonstrated in the following figure. Observation angle is important because retroreflective light is returned as a narrow cone with the inner part of the cone being most intense. Therefore, the light appears brighter to a normal car driver sitting lower and nearer to the headlights, than to a lorry driver who sits higher above the headlights.
Typical road markings
l https://www.google.com/search?ei=2BG2W4r_ HoHfrQHyh67YDg&q=road+marking+paint+principles&oq=road+marking+paint+principl&gs l https://en.wikipedia.org/wiki/Thermoplastic_road_marking_paint l http://boytekma.com.tr/_uploads/catalog/ road-marking-handbook.pdf l http://ijtte.com/uploads/2015-06-30/ 935be804-5cfe-5676IJTTE_Vol%205(2)_6.pdf