CARB Get’s It Wrong, Again – 55% Overestimate Of Truck And Bus Emissions

An independent study of the California Air Resources Board’s (CARB) on-road in-use diesel regulation indicates that the agency has again overestimated emissions and the need for regulation.

As has been widely reported, CARB has been accused of out-right fraud with respect to its assessment of the health risks posed by exposure to diesel emissions. Following publication of a study published in April by Sierra Research, an independent Sacramento-based air quality consulting firm, CARB admitted that its estimates of emissions from off-road construction equipment, which it used to justify its regulations, were inflated by more than 340 percent.

Now CARB is admitting that the emission estimates upon which it based its on-road diesel regulations were also inflated by 30 percent. Another Sierra Research study commissioned by a group of diesel truck owners and organizations representing a variety of commercial interests known as the Ad Hoc Working Group indicates that even CARB’s most recent estimates are still off base by an additional 25 percent.

Specifically, the Sierra Research study found that when recent data from a survey of Ad Hoc Working Group members were analyzed in combination with available data regarding the average maximum mileage accumulation by trucks and CARB’s own “low growth” economic forecasts, the actual NOx emission levels without the CARB regulation will be equal to those CARB originally forecast under the regulation.

In addition, Sierra found that the updated inventory for PM indicated that the additional reductions in emissions needed to reach CARB’s regulatory goals are smaller than those envisioned by the agency at the time the regulation was adopted.  Sierra’s efforts indicated that the CARB on-road diesel inventory cannot be reasonably or thoroughly reviewed based on the information currently available and that where a review is possible, there are substantial issues that need to be addressed.

“Unfortunately this follows a sequence of bad decisions and unsupportable conclusions by CARB involving a variety of regulatory endeavors,” said Jay McKeeman, vice president for government relations, California Independent Oil Marketers Association.  “CARB needs to start over if they wish to maintain any credibility as an objective, thorough, data-driven agency,”

“Yes, we need a do-over,” said Lee Brown, executive director for the California Dump Truck Owners Association, a member of the Ad Hoc Working Group.

“Businesses have already absorbed millions of dollars in equipment devaluation and new equipment purchases due to adoption of regulations that are now being found to have little basis in reality,” Brown said.  “This multi-billion dollar regulation must be revaluated immediately before more California businesses close their doors”

The Ad-Hoc Working Group commissioned the independent study because CARB staff has repeatedly refused requests for the underlying data in the emissions models and inventories prepared in the run-up to the 2008 Truck and Bus Rule.

The group has also been persistent in asking for an independent science study on CARB’s public health determinations after it was discovered the first science report was authored by a CARB researcher who faked his credentials as a PhD in statistics.  Since then, serious allegations have surfaced that CARB conclusions have been skewed by concluding there are serious health effects from diesel emissions, when underlying data shows just the opposite.

For more information or copies of the new report Executive Summary contact Lee Brown, CDTOA at 909-982-9898, or by email at

Source: William E. Davis, Executive Vice President

Southern California Contractors Association

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