Time To Reflect
article taken from Traffic Technology International
Helping road users see the difference Good-quality lane markings are a relatively low-cost traffic management measure with potentially huge benefits. With great advances being made, should you be thinking about revising your road safety strategy?
Those involved in road markings feel that their products are the unsung heroes of the traffic industry. Whether true or not, it's hard to ignore the noise they're making in relation to reducing accidents. An essential ingredient in creating a safer and more efficient road environment, they go about their business quietly, providing a constant stream of visual information that ensures smooth and, most of the time, cordial traffic flow. One man who know bucket-loads about the application of road marking - and paint in particular - is Peter Blundell, a technical expert with the UK-based company Leighs Paints. He doesn't even pause when he reveals that the key to a good road marking is retro-reflectivity. 'The retro-reflectivity given by a termoplastic line is of a finite life,' he says, because by its very nature it wears away and erodes. Thermoplastics have been dominant in the UK market for many years, but a catalyst came when performance road markings were introduced in August 2000 following the withdrawal of BS 3262 and the introduction of BS EN 1436, bringing the UK more in line with European standards. The emphasis is now more on the performance needs of road users as opposed to trying to achieve a specification. 'If you drive in mainland Europe,' Blundell continues, 'you'll notice there aren't as many road studs, as the quality of lines is so good that you don't need them. Road studs were introduced in the UK mainly because the road markings were rubbish.'

Optical Solutions

Rubbish is a label you can't stick on wet-night visibility road markings, which Blundell believes are the most influential development in the sector in recent years. Conventional thermoplastic lines will allow rainwater to pool on top of the line, meaning you can't see them on a wet night. With 50% of accidents occuring during dark, wet nights, despite these conditions only accounting for 10% of the time, solutions that improve safety when road users are at their most vulnerable have been developed.

Leighs Paints started supplying methyl methacrylate (MMA), or 'cold plastic',

NiteSite Roadmarking with close up on beads

to address the challenge of wet=night visibility and now offers two ranges, one of which is NiteSite. Featuring a splatter design/structure profile, this prevents rainwater from pooling on the surface, allowing the embedded glass bead to relect light back to the driver in wet conditions at night.

Graham Harper is a senior technical advisor with Cheshire County Council in the UK and is a huge fan of MMA. He remembers first being impressed by its potential at the Road Safety Marking Association conference in November 2002 and subsequently deployed NiteSite on the A556 in March 2003. Performance evaluations conducted at the start of this year clearly highlight its effectiveness.

'The true test of a road marking is its ability to make the highway safer, while providing value for money. In both respects, I am pleased to say it has done just that. In the three years post-application, we have seen personal injury accident figures drop from 16 to 6, with no wet-night accidents at all, providing a first-year rate of return of 550%'

Challenges

But not all local authorities are as keen to cough up for MMA, and this is a challenge for companies such as Leighs Paints. 'Road markings have historically been considered an evil necessity - cheap and cheerful,' Blundell suggests. 'There is also an unwillingness from contractors to put markings down that they know will last four or five times longer.'

Phil Chadwick from the US company Potters Beads agrees in part. 'The problem with contractors is that some of them are cowboys,' he claims. 'The industry needs a shake-up. There's too much capacity in contracting - anyone can buy a machine and start laying white paint. Because of the nature of the job, it tends to entrepreneurs, but not a lot of technical people: they might be focused more on making money rather than improving road safety. Some local authorities just don't understand that if they go for better products, they can safeguard their futures.'

This is why Harper in particular remains convinced about MMA: 'It is important to focus on the long-term views with these types of road markings - the whole-life costs,' he says. 'Although it is true that they are three times the cost of traditional theromplastic markings, savings are made not only in accident-reduction terms, but reduced traffic management costs, enhanced wet-night visibility benefits for the older driving population, and reduced disruption to traffic over the six-year life expectancy.' Price is, he concludes, one of the most important factors and is often overlooked by engineers.

'There is generally less emphasis placed on road markings than there is on the road surface,' Chadwick suggests. 'More people are concerned about potholes, or cracks in the road, which, in reality have little impact on road safety. Sure, they make a mess of your axle, if you drive over them, but road markings can actually reduce accidents.'

The Touch of a Button
COST 331 established a national policy for road marking design as a result of the influence that markings can have on road safety

In 1999, a European transport research project (COST 331) was published on the requirements of horizontal road markings, and concluded that drivers need a minimum reaction time of 1.8-2.0 seconds to safely maintin their position on the highway - a reaction time that varied with the quality and width of road marking. At present, most national technical specifications regarding road markings stipulate more or less appropriate parameters defining essential requirements (night-time and daytime visibility and anti-skid properties), as well as design parameters, without always taking into account the driver's real visibility requirements.

Most research in this area concentrates on the development of new marking products that meet the above mentioned requirements for as long as possible (maximum functional life), and the development of new technologies for the manufacture of high performance equipment to assess those requirements.

Researchers involved with COST 331 established an up-to-date scientific method to determine the optimum road marking design to ensure that markings are visible during the day and night, and under all weather conditions, while taking into consideration the visual needs of drivers. A compter software visibility model was then written to aid authorites in the design of markings. The model suggests that the 'visibility level' of a marking is mostly the function of the luminance contract between the marking and the roadway surface and the size of the pavement marking. This would seem to indicate that wider markings do provide a benefit to target detectibility.

Claiming this model to be 'bloody marvellous', Peter Blundell from Leighs Paints believes COST 331 is the best thing since sliced bread.

As well as actually helping local authorities meet government targets, road markings remain a particularly cost-effective measure. And this is backed up by The Royal Society for the Prevention of Accidents' 2001 Cost-Benefit Analysis of some 43 minor road marking schemes, which showed an average first-year rate of return of 957%.

Road with NiteSite road markings at Night

Let's Get Visible

Those behind the Higher Highway Safety Standards (HHSS) Initiative in the USA will be hoping for similarly impressive returns. The HHSS calls for wider and brighter lines to be implemented on US roads to make life easier - and safter - for older drivers.

This was the ethos behind Montana DOTs Older Drive Corridor Update program, created to improve driving conditions for those over the age of 65, who - accoring to figures from NHTSA - make up 12% of the 42,000 fatalities on US roads every year. USDOTs concern is

that as the 'baby boomers' reach retirement age, the number of older drivers will increase substantially. In fact, by 2030, there could be 71 million older drivers on US roads, sparking concerns that this could have a serious knock-on effect on accident rates.

Although the causes of crashes are many and varied, the visibility of road markings often crops up in surveys. A poll conducted a few years ago by the New Jersey-based PKS research, for instance, revealed that clear, easy-to-see road lines are important to 99% of people for driver safety, while 94% believed that their states and authorities should make easy-to-see lines a priority.

The goal of the HHSS is therefore to persuade US states to widen road markings from the current 4in to between 6in and 8in, which would help reduce strain and fatigue, and enable drivers to respond more quickly to upcoming road conditions.

Widening lines is simple but has proved to be effective. Montana DOT recorded an 18% reduction in crashes involving older drivers. As far back as 1992, Florida DOT went down the same route and crashes were reduced by 16%. Michigan was once ranked fith in the USA for the number of older drivers killed in crashes, so as well as widening the white fog line on the side of the road from 4in to 6in, the state's DOT moved rumble strips closer to the edge line so that users were alerted to the fact that they could be veering off the road earlier.

Improving the visibility of road lines is a logical way to improve road safety and easily rectified according to Richard Neumann from Swarco. The company's stance is not to favor one particular system, however but to take a horses-for courses approach. 'Both cold plastic and theromplastic are very durable materials. The choice as to which material suits an environment can only be judged on an individual basis, based upon factors such as traffic impact, location of the white lines, national preference, etc.'

According to Neumann, the crucial factor is not so much the material, but rather the shaping of the road marking - i.e. the structuring. 'Only structured road markings with high-quality beads are able to create good wet-night visibility. We have conducted extensive research and testing with structured road marking systems and are also involved in larger 'test decks', like the one in the Harz region in Germany (the B4 between Bad Harzburg and Torfhaus), where different types of structurings and profiles are studied for their resistance against snowplows.'

Neumann agrees with Phil Chadwick from Potters Beads that the quality of the sphere is also a vital factor in creating good retro-reflectivity in the wet. 'Our standard-class beads are made from reclaimed soda-lime glass, which is basically recycled window glass,' Chadwick reveals. 'They work very well, but they have limitations in that it's just standard glass.'
There are a mere handful of companies around the world who produce what is known as high reflective index glass - or high-index beads. One of these is Flex-O-lite, which is now owned by the PQ Corporation (after being bought from Jackson Products in January 2007), which also ownes Potters Beads. These high-index beads boast a reflective index of 1.9, whereas standard glass beads only have an index of 1.5. 'They basically shine like crazy,' reveals Chadwick, 'and have been used for many years in airport runway applications. We're just starting to introduce these into the roads business.'

Coming Next

The next generation of spheres are those that can reflect under water; 'By using high-index beads, you can actually achieve a reflective index of 2.4,' says Chadwick. 'However, the focal point of these types of bead is actually outside of the bead, so you need a layer on the top of the bead to refocus the light for you - which is usually rainwater.'

Using a new glass formulation and a specific forming technique, Swarco is producing beads with refractive index of more than 2.1. The plus9beads range is

Cold Plastic road marking machine in action

described by Ricahrd Neumann as 'close to perfection.' Manufacturered from the 'purest' raw materials and shaped to the finest microspheres of nearly 100% roundness, the quality and uniformity of these particular spheres offer what he claims to be 'outstanding' retro-relectivity performance.

Larger beads are also an option to improve visibility and safety, accoring to Jon Sproul, general manager of Swarco America. 'US states are starting to amend their theromplastic specifications to include big beads as part of the glass bead rop-on specifications. When double-dropped onto thermoplastic with the standard smaller beads, marking provide reading that are typically 75-100% higher than a single drop of Type 1 AASHTO. The larger beads also provide an added safety feature by offering improved wet-night visibility and reflectivity during wet-night driving conditions.'

Sproul states that this parctice has worked to good effect in South Carolina and Florida, and was also included in the Alabama specifications in January 2007. 'We have been able to effectively double the reflectivity values on thermoplastic by adding the double-drop glass bead application technique,' confirms Chester Henson from the Florida DOT. 'Before the change, we were struggling to get 200-250mcd on yellow thermoplastic and now we are consistently getting 400-450mcd.'

'But the application trucks in the UK are not geared up for double-drop,' admits Chadwick. 'Around 99% of them use a single-drop system, but to achieve the best possible wet-night and dry-night visibility, a combination of beads is often needed. Sometimes you might need three, or even need to add an anti-skid glass grain. All of these products might be slightly different in terms of particle size and density. Coatings can also be quite critical, as some will embed the bead in the marking more than other coatings. You can blend the beads in a tank before sending them out to the customer - which is what we do here - but there can be segregation issues.'

'If the UK is going to catch up with the USA - which in terms of road markings is the leader - it needs to change its application methods. This means you're going to need two things: contractors who are willing to invest in double-drop systems, with two bead tanks, two bead guns, etc, therefore providing complete flexibility; and local authorities who are willing to think about the long term, rather than short-term budgetry constraints.'