Raised retroreflective pavement markers are an asset both economically and socially, but they must be maintained. Technology is ensuring that testing is carried out efficiently, so that the road safety budget can go further.

Visibility is a key factor in road traffic safety. To assist and guide road users, several countries use raised retroreflective pavement markers, so-called road studs, to supplement road markings and traffic signs.
They come in a variety of shapes, colors and materials, and serve as horizontal guiding devices that reflect light from the headlight back to the driver. Road studs may be constructed from one or more integral parts, and may be bonded to, anchored on or embedded within the road surface.
Although pavement markers are available that are compatible with snowplows, countries with colder climates and frequent snowfalls usually use fewer road studs. For example, Switzerland does not use retroreflective pavement markers, while in the UK they are very widespread.
Local standards
There are numerous local standards and regulations to be observed. In Europe, the most important standards are EN 1463-1, which defines the initial performance requirements, and EN 1463-2, which outlines road test performance specifications. In the USA, the Manual on Uniform Traffic Control Devices (MUTCD) defines the nationwide standards applicable by road managers for the installation and maintenance of traffic control devices on all public streets, highways, bikeways and private roads open to public travel. While the MUTCD states general requirements and application regulations, the US standard ASTM E1696 defines specifications for field measurements. ASTM E1696 is not only used in the USA, but also in many other countries. Some states supplement the MUTCD with their own specific rules. For example, the state of Illinois released a supplement with a whole chapter about the inspection of reflective pavement markers.

PM Zehntner Testing visibility measuring geometry road studs EN 8192

Measuring principle of field mesurements of raised retroreflective pavement markers, the observation angle requirements of road stud measurements differ, depending on the country developed for


Regular field tests

To guarantee ongoing traffic safety, an initial performance test is not sufficient. Retroreflective pavement markers are subjected to wear and tear, so regular field tests and a structured maintenance policy are required to ensure that repairs or replacements are carried out in due time.

While it may make sense to carry out the initial performance test in a laboratory using a goniophotometer, it would be a waste of time and material to extract raised pavement markers from the road for field tests. It is
much easier and more cost-efficient to use a handheld retroreflectometer for on-site field measurements of the night visibility (coefficient of luminous intensity R and RI) without extracting them. Zehntner offers the portable handheld retroreflectometer models ZRP 6030 and the newly launched ZRP 6030+. The operator simply places
the retroreflectometer onto the pavement marker and, with a press of a button, the night visibility, ambient temperature, relative humidity and, optionally, the GPS coordinates, are recorded. The night visibility measurements are related to the visual observation as seen by a car driver at distances of approximately 220m (722ft) or 440m (1,444ft) for trucks, both under low-beam headlight illumination.

Zehntner retroreflectometers are appreciated worldwide for their fast and easy operation, as well as their Swiss precision. The new ZRP 6030+ comes with a 5.7in (14.5cm) high-resolution color.

Zehntner ZRP 6030+ in use

Zehntner’s ZRP 6030+ Retroreflectometer is used to measure the night visibility of road studs in the field


Maintenance management
When Qatar-based infrastructure company Al Jaber & Makhlouf was contracted to supply road markings for the Hamad International Airport (formerly the New Doha International Airport), it had to observe the regulations set by the ICAO. As such, high-precision testing instruments from the Swiss manufacturer Zehntner were used for the initial acceptance inspection. This is just one practical example of maintenance management for ground signs and markings.

For such measurement jobs, Zehntner offers a variety of Swiss quality retroreflectometers that are fast, precise and easy to use. The user has a choice between three different handheld units, which are suitable for small- and medium-sized airports:

ZRM 6006 the ZRM 6006 with one-button operation
ZRM 6013+ the ZRM 6013+ with additional memory, PC and printer interface
ZRM 6014 and the ZRM 6014 with additional unique options and optimized user comfort


For large, busy airports, the sophisticated, vehicle-mounted ZDR 6020 Dynamic Retroreflectometer RL may be the best choice as it can cover a large area quickly at traffic speed – minimizing or even eliminating the need to close runways, taxiways and ground traffic roads. The measuring head can also be mounted on other testing vehicles such as friction testers. Traffic signs can be measured with the various models of the ZRS 6060 Retroreflectometer.

Zehntners-retroreflectometers for all needs and budgets

Zehntner designs retroreflectometers for a variety of needs and budgets


Software support
Assisted by Zehntner’s free mapping and data analysis software, „MappingTools“, the management of retroreflection measurements becomes fast and simple. They can be evaluated to individual specifications and the results can be displayed in charts, tables or on a map. For maximum compatibility with existing systems and procedures, measuring reports can be generated in several languages, as PDF or Microsoft Excel files.
Furthermore, the data can be exported to an external GIS (geographic information system).


Zehntner’s „MappingTools“


Author:            Sévérine Berger

Company:        Zehntner GmbH Testing Instruments, Switzerland

Telephone:       +41 61 953 05 50

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Website:          www.zehntner.com