With the advent of autonomous and semi-autonomous vehicles, efficiently surveying and maintaining the quality of road markings has never been more important when it comes to safety.
Autonomous and semi-autonomous vehicles are now being driven and tested on our roads. Improving road safety is a key factor in these developments. Today’s production cars already have automated navigation, lane-keeping and parking functions. These vehicles rely on a suite of sensors to provide real-time feedback of road conditions, allowing onboard computers to make safe decisions. One such sensor will be a multi-camera vision system looking at road markings, lines and road signs. It is not possible to crowd source retroreflective measurements, as the lights and cameras in current vehicles are not calibrated and do not have an accurate CEN 30 geometry.
Why are road markings necessary?
The essential purpose of road markings is to guide and control traffic, supplementing the function of traffic signs. Markings also serve to signify the segregation of traffic lanes and clearance from hazards. In an autonomous vehicle future, road markings will augment lane detection and will also continue to provide the vehicle (and its user) with a clear lane delineation.
What quality of road markings in day and night conditions will autonomous vehicles require to operate efficiently and safely for all road users? That is the burning question that global road authorities and road maintenance companies are asking manufacturers of autonomous cars. Many cars today have lane departure warning systems that use the line markings, for example, Tesla Motors incorporates lane line detection in its cars fitted with an autopilot system and many other car manufacturers are following its example.
Fading lines
All these autonomous vehicle systems assume that line markings exist, are clear and, more importantly, are visibly distinct. However, as with most UK roads the line markings can often be faded or dull, which means that a longer lasting material is often preferred for automated vehicles.
Industry executives say that inadequate infrastructure has become a roadblock to the development of self-driving cars, vexing engineers and adding time and cost to installations. Poor markings and uneven signage on the three million miles of paved roads in the USA are forcing automakers to develop more sophisticated sensors and maps to compensate. According to the European Transport Safety Council, EU rules on road infrastructure safety should also be revised to meet the needs of such vehicles, for example, to mandate clear markings on all roadways.
Road authorities strive continuously to maintain safe and efficient road networks but struggle with limited funding. Consistent quality control with regular monitoring ensures that funding helps improve road safety and will not be wasted on under-performing maintenance work.
What are ‘visibly distinct’ markings?
Vehicle manufacturers may consider that existing road-marking, marker and sign standards are all that is needed for autonomous vehicles to perform safely and efficiently, provided the minimum standards are enforced. Road markings that adhere to these standards are visibly distinct in daytime and night-time driving. Certified retroreflectometers are necessary to check the retroreflectivity of road markings.
Markings, like everything on a road surface, are subject to wear and tear caused by traffic and environmental conditions. The constantly changing condition means it is often difficult and time-consuming to monitor their quality. To maintain accurate maps of road-marking quality will require road authorities and road maintenance companies to perform regular periodic surveys, perhaps several times a year. When autonomous vehicle manufacturers finally decide upon the quality and visibility of road markings necessary for safe passage, these road-marking maps will have to be maintained (this will probably be mandated by the regulating authority).
Road authorities and road maintenance companies will require systems to continually access and monitor the retroreflectivity of road markings, to ensure they are safe, economically and environmentally friendly and legible at all traffic speeds, causing no interference to traffic flows.
