Resources

General information

The M7 specification sets out the requirements materials must meet to be included on the list of approved roadmarking products for use on state highways. This is based on the material conforming to a set of laboratory tests and meeting performance requirements assessed by an on road trial.

Properties that are used to assess the performance of a roadmarking include:

• Colour
• Degree of wear
• Skid resistance
• Luminance (Qd)
• Retroreflectivity (RL)

Luminance and retroreflectivity are the measures used to assess the visibility of markings.

Luminance is the amount of light reflected from a diffuse source, for example the brightness of marking under street lighting.

Retroreflectivity is the amount of light reflected back to the original light source, in the case of roadmarking this is how much light from vehicles headlights is reflected back to the driver.

Retroreflectivity in roadmarkings is achieved through the use of spherical glass beads. These are either mixed into the material, or dropped on while the marking is still wet. Beads come in a range of classes depending on size and quality as defined in AS/NZS 2009. In general, markings in New Zealand use a Type B bead with a nominal size of 0.6mm. Larger beads (eg Type D) and beads with high refractive index (eg Type D-HR) for improved retroreflectivity performance are also available.

The expectation is that roadmarkings will be effective during the day and night in both dry and wet conditions.

Figure 1: comparison of markings in the dry and wet (Photo courtesy Potters Industries)

Background

Roadmarking materials are currently specified under two documents

• M7 – 2009 Specification for roadmarking paints
• M20 – 2003 Specification for long life roadmarking materials

There are certain limitations with both these specifications, firstly the age of the approved products list means that several products are no longer available and secondly there is no wet retroreflectivity requirement (figure 1).

Changes to M7

Recognising the above issues, the M7-2017 specification was developed to include the following changes:

• Update the NZ Transport Agency specification M20 Long life roadmarking materials and incorporate it into M7 to provide a single specification for roadmarking paints and long life products
• Have separate approval lists for markings on asphalt and chipseal surfaces
• Introduce two levels of visibility performance; a standard visibility class in line with current practice and a high visibility class (refer table 1)
• Include a wet retroreflectivity requirement (Wet RL) to meet the need for visibility of markings in wet conditions.

Table 1: visibility criteria for white products (mcd/m2/lux)

At present, high visibility markings are suggested for use where a safety audit identifies improved wet delineation is required. Modelling suggests that there could also be a benefit on un-divided roads that fall into the High Volume, National and Regional One Network Road Classifications (ONRC) however work is being undertaken to confirm this.

Achieving wet retroreflectivity

Long life products applied in a structured pattern (agglomerate or multidots) as applied under the P30 High performance roadmarking specification will generally meet the high visibility standard.

Specifiers should be aware that when using paint to achieve the high visibility large glass beads (Type D-HR) and thicker dry paint films, in the order of 300µm are needed. This will not only result in increased material costs but also traffic control and laying costs due to slower application and longer drying times. This will be partly offset by the expected doubling in life in comparison to standard markings.

In some instances, such as in areas with winding alignments it may be more cost effective to use a long life product (thermoplastic or cold applied plastic) with quicker drying times.

Retroreflectivity and safety

Recent research suggests that the use of markings with better visibility in the wet can result in a crash reduction of up to 5%. Other benefits of higher visibility markings include reduced driver fatigue and improved visual guidance which decreases the likelihood of drivers losing control of their vehicles. This is particularly the case for older drivers.

2017 approval list

The new specification and approval list no longer requires users to specify a paint thickness for roadmarking; rather they will select a product class (refer table 2) based on the surfacing type, durability and visibility level desired. A supplier then nominates an approved system, this could include a material type and thickness, bead type and application method that will achieve the desired properties.

Products should now be selected from the M7-2017 approval list. The M7-2009 approval list will be invalid from December 31, 2017. This overlap is to allow suppliers and roadmarkers to use up any remaining stocks of previously approved materials.

For existing contracts, guidance is provided in table 3 on converting the M7-2009 and M20-2003 classes to the M7-2017 classification system. The durability classes (normal, extended and long) in table 2 equate to approximately 1.5, 2.5 and 5 million vehicle passes respectively.

Table 2: approval classifications

Table 3: Conversion of new approval classes to earlier specification systems

Implementation of M7-2017

M7-2017 will initially be released as a pilot specification; this means that advice should be sought from the NZ Transport Agency Technical Services team prior to its use. This is to ensure that where high visibility markings are desired, that an adequate testing and monitoring regime is in place.

It is intended to trial M7-2017 on specific sites across the country over the next 12 months in order to:

• Allow suppliers and contractors to fine tune the methodologies needed to meet the high visibility class requirements
• Let specifiers familiarise themselves with new requirements in terms of selection
• Measure the performance of these lines to gain data on deterioration rates under New Zealand conditions.

NZ Transport Agency NOC Managers, in conjunction with contractors will be asked to volunteer sites in their areas. The aim is to get a mix of different materials, suppliers, contractors and climatic areas.

Criteria for selecting sections of road include:

• Annual average daily traffic in the range of 2,500 to 5,000 vehicles per lane with about 10 percent heavy vehicles
• A speed limit of 80 km/hr or greater is preferred
• A length of continuous edgeline. A centreline or lane lines between multiple lanes of traffic in the same direction could be considered
• The ability to include four 5m long sample areas where trafficking of the lines is expected, for example the edgeline on the inside of a corner. The sample areas should be spaced approximately 300m apart, depending on the site
• Be distant from activities such as quarries which can produce excess dirt or gravel which will be tracked over the test area.

Data from these sites will be collected and analysed to allow for the full implementation of M7-2017 and the withdrawal of M7-2009 and M20-2003.

The M7 specification, notes and approval list can be found on the NZ Transport Agency website under the delineation page.

Publication details

Author: Janice Brass
Published: September 2017
Reference: M7-2017
Version: September 2017
Found at:  https://www.nzta.govt.nz/resources/pilot-specification-for-approved-roadmarking-products/

Further information

For further information or to discuss using the specification in your area contact the Technical Services team at pavements@nzta.govt.nz.

Kevin Reid