White lines enable road users to navigate safely and for traffic to be managed, but what goes into making them so effective?
White lines have been synonymous with road safety for over a century, and it is no coincidence that the first white line road markings appeared around the same time as the first wave of mass-produced cars.
Indeed, the idea of putting a white line down the centre of a road was first conceived by American Edward N Hines in 1911 – two years before Henry Ford established the world’s first moving car assembly line.
Today, it is easy to take such a simple innovation for granted, but the enormous impact white lines have had on road safety – helping motorists around the world to maintain lane discipline, and avoid oncoming traffic and other potential hazards – cannot be overstated.
The effectiveness of white line road markings owes much to chemistry, and specifically, to titanium dioxide (TiO2). White line markings can only serve a purpose if they can easily seen by all road users, in all conditions. TiO2 plays a crucial role in ensuring this is the case.
TiO2 is among the brightest white substances in the world, and the way it interacts with light means, even at night, or in poor weather conditions, white road markings display prominently in car headlights. This gives motorists the best possible chance of following the road safely.
How do white line road markings work?
White line road markings are made using thermoplastic resin, mixed with titanium dioxide pigment and glass beads.
The pigment provides a bright white, highly visible colour, and beads act as ‘retroreflectors’ – which means they reflect some light back to its source.
At night, the light from a car’s headlights will reflect from the markings back to the driver, helping them to see the road easily.
Can other pigments do the same job as titanium dioxide?
No other pigments can offer the same all-round quality in the same quantities.
While other substances, such as barium sulphate and kaolin, can replace certain amounts of TiO2 in formulations, they lack the opacity of TiO2 and can never replace the entire amount. In addition, far higher dosages of barium sulphate are required to achieve a comparable result – making TiO2 a more cost effective solution – not to mention the fact that market supply of TiO2 far outstrips that of barium sulphate.
Consequently, TiO2 is the principal white pigment used in the world today – especially in this application. Due to its high reflectivity and durability, it combines the highest degree of safety with the most efficient of resources.
Contributing to better road safety
Used in white markings, TiO2 helps to prevent traffic accidents by making it possible for drivers and cyclists to travel safely. Without bright white road markings, more and improved street lighting could be required, with high economic cost.
Many countries have specific requirements to ensure that road markings are bright, visible and clear.
Within the EU, for example, road markings are required to meet minimum performance standards, based on their luminance, day-time visibility, night-time visibility, skid resistance and durability.
Such standards are perhaps part of the reason we are living in an age when road safety standards have never been better. Since 2010, the number of fatalities recorded each year on EU roads has fallen by nearly a fifth, and the EU has a strategic target to halve the number of road deaths between 2010 and 2020.
While there is a huge range of factors that contribute to road safety – from improved safety features on vehicles to better driver education and awareness – titanium dioxide certainly has an important role to play.
-  Travel & Leisure: Why the Lines on Our Roads Look the Way They Do
-  Ford: The Henry Ford Story
-  'Analysis of the socio-economic impacts of a harmonised classification for titanium dioxide' - report prepared for the Titanium Dioxide Industry Consortium, December 2016
-  EU Road Federation: White Lines Save Lives
-  European Commission: 2016 road safety statistics: What is behind the figures?