For trucking companies, going green isn’t just about making regulators happy.

Increasingly, the companies that use truckers’ services are being asked by shareholders and by government to improve their sustainability. Many see emissions from the trucks that deliver their goods as a big contributor to their overall carbon signatures. That has created a demand for clean trucking.

Calstart, the California-based nonprofit dedicated to greening up the nation’s transportation sector, saw the need for a definitive measuring stick to provide a green measurement for truck operators.  It shows companies how well they are moving moving toward the national goal in 2050 of an 80 percent reduction from 2010 tailpipe emissions levels.

Working with the the National Association of Fleet Administrators, Calstart helped develop a sustainable fleet accreditation program — a trucking industry version of the U.S. Green Building Council’s LEED certification program for residential and commercial construction.

Already major trucking company users such as Walmart and Target are giving contract preference to trucking fleets that can demonstrate increasing levels of clean emissions and fuel efficiency. Many government agencies are required by state or local rules to reduce the impact of their vehicle fleets.

The NAFA Sustainable Fleet Accreditation Program enables fleet managers to show third-party verification of their progress.

“It helps fleets measure themselves against each other” and enables potential clients to measure the relative “greenness” of trucking companies bidding for their business, said John Boesel, Calstart’s chief executive.

Related: “Calstart: Easing the Way to Cleaner Trucking”