Road Markings - Setting New Boundaries for Safety
Two key issues currently driving technology for road markings materials revolve around public safety and health. With growing concern over pollution and more accidents occurring at night and at pedestrian crossings than ever before Frances Cook takes a closer look how these issues are influencing the type of materials being chosen for use on our roads.
Around one-third of road accidents in the European Union happen at night despite the fact that only one-fifth of all traffic flows after dark - and many of these accidents occur at pedestrian crossings. According to EuroTest Mobilitiy, which carries out the EuroTest pedestrian crossing assessment (EPCA) each year, almost 2,000 of the 8,000 pedestrians killed annually, die in accidents on or in the vicinity of a pedestrian crossing.
From 2008 to 2010 pedestrian crossings havebeen tested via the EPCA in 44 cities in 23 European countries and results showthat since the first test in 2008 to date, ever higher numbers of crossingsfail the basic safeness test: one in eight in 2008, one in six in 2009 and onein five in 2010.
Prismo - part of US-based Ennis Paint - has developed Zebrabright, an advanced marking system, particularly for use at zebra crossings. The product, a Methyl Methacrylate reactive paint (MMA) with embedded white Clusterbeads, is a development from the company's Clusterbead technology and also its Colourbright product, which previously received the European Innovation Award.
The markings project light back at the approaching driver, highlighting the white surface on the pedestrian crossing,and are made up from a cluster of high index glass beads approximately 2mm in size. Prismo's Technical Director Steve Owens explains. "The result of the system is a highly reflective zebra crossing white pad that gives greater than 700mcd/lux/m² dry night time visibility and greater than 100mcd/lux/m² wet night time visibility.
When the product was tested by Nottingham County Council, the new system increased retro-reflectivity by more than five times the normal standard, which surpassed expectations.
The readings of millicandelas(mcd) have been described as "remarkable" by the council who explained that they would have been content seeing readings over 150mcd.
Another company involved in the use of glass beads to create materials that will reflect light from the headlights of vehicles is Evonik with their Degaroute product. Titanium dioxide is also mixed into the cold plastic because it acts like a mirror when combined with the glass beads.
Confirmation of its contribution to road safety occurred last year when the British trade journal Highways Magazine awarded the Degaroute-based marking Road Safety Product of the Year.
Its efficacy had been proved after it was applied to a stretch of motorway near Chester in the UK where the result was a 50% reduction in traffic accidents.
Materials munching pollution
While titanium dioxide is commonly used in road markings, scientists at Eindhoven University of Technology in the Netherlands have been developing a new concrete material that is coated with titanium dioxide to reduce air pollution. The product removes nitrogen oxides and uses sunlight to convert them into nitrate, which can be washed away by the rain.
According to Professor Jos Brouwers, testing was carried out recently in the Castorweg, city of Hengelo, where the area consisted entirely of these new DeNOx stones. "In this street we have actually measured the reported reductions in NOx," says Brouwers going on to reveal that nitrogen oxide reductions have been as much as 35%to 40%.
Poor air quality isnow considered one of the biggest health issues in Europeand as a result the development of materials with an ability to "eat" pollutionis increasing, since air pollution continues to increase while air regulations become more and more strict.
A committee included evidence that air pollution could be contributing to 50,000 deaths in the UK a year and a study commissioned by the mayor of London, calculated that more than 4,300 deaths are caused by poor air quality in London each year (costing around £2bn).
NOx is primarily made up of two pollutants: nitric oxide (NO) and nitrogen dioxide (NO2). NO2 is of most concern due to its impact on health.
However NO easily converts to NO2 in the air, so to reduce concentrations of NO2 it is essential to control emissions of NOx.
For this reason Brouwers's discovery could make for a very big break through in road materials and markings.
Organic yellow lines
While levels of NO2 continue to exceed national air quality objectives, the concentration of lead (which has historically been a problem along with sulphur dioxide), is now at manageable levels. Two of the companies leading the way for the reduction of lead in road markings are Euromark and Ringway, who joined forces to develop "organic" yellow lines.
Many yellow thermoplastics rely on lead chromate to achieve the limits set in current standards for chromacity and luminosity and as a result are identified as "high hazard" in assessments under the COSHH (Control of Substances Harmful to Health) regulations. Ringway's Eurolite Organic Yellow is virtually free of trace heavy metals and "low hazard" and more environmentally friendly.
"We eventually selected an organic pigment that we were able to modify so the colour and luminance of our finished product fell within the range set out in the British standards," says Neville Smith, Euromark Chemist and Technical Manager.
The new material is heated and applied in the same way as conventional thermoplastics. Following a year-long trial at Junction 37 of the M4 in Wales it passed laboratory testing by the British Research Establishment and Euromark is now producing Eurolite Organic Yellow under its Kitemark licence.