European Directive:

A European Directive 2008/96/EC of the European Parliament and of the council on road infrastructure safety management was issued in 2008 and represents a legal basis for Road Safety Inspections (RSI) in the European Union. All members of the Trans European Network (TERN) must introduce the European Communities (Road Infrastructure Safety Management) Regulations requiring Governments and Road Authorities to carry put periodical road safety audits and safety inspections which include the retroreflective properties of road markings.

From a combination of the above legislative and also technical requirements for OECD countries to maintain minimum retroreflective standards for road safety and sustainability in Europe and USA, the Road Marking Evaluation and Management Industry need to carry out extensive and currently very expensive Road Safety Inspections and surveys for road lines/markings.

These standards are also been adapted by other countries worldwide. The momentum is moving in the direction of countries that enforce the legislation and not relaxing the standards. There is a worldwide drive to reduce car crashes, injuries and car related fatalities because of the substantial socio-economic impact these have on countries.

USA:

The Manual on Uniform Traffic Control Devices (MUTCD) is a document issued by the Federal Highway Administration (FHWA) of the United States Department of Transportation (USDOT) to specify the standards by which traffic signs, road surface markings, and signals are designed, installed, and used. Pavement markings are an accepted method to communicate both the intended travel path and roadway alignment for drivers during day and nighttime conditions. To ensure consistent application of pavement markings, their characteristics and warranting criteria are described in the Manual on Uniform Traffic Control Devices (MUTCD).

MUTCD Section 3A.03

MUTCD Section 3A.03 requires agencies to use a method designed to maintain longitudinal pavement markings to a minimum level of retroreflectivity. The Federal Highway Administration (FHWA) believes that this change will promote safety while providing sufficient flexibility for agencies to choose a maintenance method that best matches their specific conditions.
Read current version HERE.

The Federal Highway Administration (FHWA) are currently waiting on a final rulemaking from congress expected during 2015 in relation to setting US minimum retroreflectivity standards for road markings on all public roadways.
Read the MUTCD final proposal for these new minimum retroreflectivity standards HERE.