Californian air quality regulators may delay implementation until 1 January 2014 of some diesel-emission requirements for forklifts and other off-highway vehicles.

The California Air Resources Board (ARB) might increase the enforcement exemption for some "low-use" diesel-powered equipment, including forklifts. A proposal calls for adjusting the threshold to 150 hours a year from the current less-than-100 hours a year, in part because ARB analysis projected a low emissions cost-benefit in requiring retrofits for limited-use equipment. The 100-hour threshold is slated to expire on 31 December.

Representatives of ARB and the trade organisation Associated General Contractors of America agreed on 7 October to several changes in diesel-emission rules. The off-highway regulation was first adopted in July 2007 and calls for installation of diesel soot filters and replacement of older, dirtier engines with newer emission-controlled models.

Originally, ARB scheduled improvements to start in March 2010 for larger fleets and staggered through to 2015 for small-sized fleets.

A proposal delays the start of requirements by two years for all fleets with most fleet implementation dates going to 2017. ARB says a proposal would "allow turnover in lieu of retrofitting so no fleet is ever forced to apply an exhaust retrofit".

Sacramento-based ARB is scheduled to consider the enforcement extension and streamlining proposals during a 16-17 December meeting. ARB is a department of the California Environmental Protection Agency.