Caltrans Narrows Freeway Widening Project : Transportation: Plan now calls for 10 lanes on the Santa Ana instead of 12, in response to officials’ fears of more car traffic and pollution.

At the insistence of regional and federal officials, Caltrans has agreed to scale back the widening of the Santa Ana Freeway from 12 lanes to 10 along one key stretch of highway.

The U.S. Environmental Protection Agency and the Southern California Assn. of Governments had complained that Caltrans’ 12-lane design would would attract too many cars and worsen air quality.

The dispute involved Caltrans’ use of a continuous lane in each direction that would have been used for merging traffic between on-ramps and exits. Such lanes, known as auxiliary lanes, normally reduce pollutants by easing traffic congestion.

But the EPA and SCAG, a six-county regional planning agency, ruled that Caltrans’ plan effectively turned the auxiliary lanes into regular lanes and as a result would have attracted too many single-occupant cars.

The freeway will still include the conventional merge lanes that extend from an on-ramp to the next off-ramp. The decision affects the section of highway between the Garden Grove and Riverside freeways.

“I’m not an advocate of this, but I’m doing this because it’s the law,” said Barry Rabbitt, Caltrans’ Interstate 5 project manager. “We’re certainly not wanting to build facilities that are in conflict with other public goals.”

The dispute over merge lanes is part of a recurring clash between government agencies over how to improve traffic conditions without spurring usage that would erode hard-won gains in air quality.

In another example, SCAG and the county’s tollway agencies are embroiled in a fight over car-pool lanes. The association wants three new toll roads to open with car-pool lanes, instead of waiting to see if they’re justified by traffic volumes. Also, the association is proposing that the tollway agencies charge car-poolers less in order to make the special lanes more attractive.

A report released Wednesday by the Orange County Transportation Commission warned that such clashes threaten to delay many of the highway projects included in Measure M, the ballot measure that authorized a half-cent sales tax for transportation improvements.

Regional and federal officials have taken the position that “the construction of new roads inherently causes growth and a resulting increase in air pollution,” the report states. “This is a debatable position, but it could lead to delay in the implementation of transportation projects in Orange County.”

Prepared by Spinner-LaMar & Associates, an Irvine-based public affairs consulting firm, the document recommends that OCTC take a more active role in gaining a regional consensus on Measure M projects before delays occur.

Specifically, the report suggests that the commission appoint representatives to various SCAG committees and other regional groups that are involved with the association and the South Coast Air Quality Management District.

The OCTC board will consider the report at its meeting on Monday. Commission officials were unavailable for comment.

Last week, the county’s legislative delegation wrote to the EPA seeking relief from regional officials’ decisions involving the Santa Ana Freeway.