Air Quality & Emissions, California, MTC, SB 375

ARB releases draft greenhouse gas targets for SB 375

The State Air Resources Board (ARB) is required to set emissions reduction targets this year for the initial planning cycle set in motion by Senate Bill 375.  These targets reflect regional goals for reducing greenhouse gas emissions from passenger vehicles and light duty trucks.  The bill requires that ARB release draft targets by June 30 in preparation for final targets, which will be set by September 30.  ARB met the first deadline, releasing draft targets yesterday.

The greenhouse gas targets are expressed in terms of percentage per capita reduction from 2005 levels.  Here are the draft targets:

Region (MPO) 2020
[ARB Draft Target]
Bay Area (MTC/ABAG) -5% -5 to -10% -3 to -12%
Sacramento (SACOG) -4% -5 to -10% -13 to -17%
San Diego (SANDAG) -11% -5 to -10% -5 to -19%
Southern California (SCAG) -4% -5 to -10% -3 to -12%
San Joaquin Valley1 -7 to +12% -1 to -7% -1 to -7%

1 San Joaquin Valley counties (Fresno, Kern, Kings, Madera, Merced, San Joaquin, Stanislaus, and Tulare) were assigned a collective target.

The first column of numbers represents MPO projections of what might be achieved in each region by 2020, under currently prevailing regional transportation plans.  The second column is ARB’s draft target, expressed for now as a range.  The third column represents a best guess as to the reductions that are possible by 2035.  At this point in time, though, there is an insufficient technical foundation to produce serious 2035 estimates.  It’s a work in progress.

How did ARB arrive at these numbers, and what should we make of them?  Probably not too much at this point, as they are just preliminary.  But they offer, if nothing else, insight into the upcoming challenges posed by SB 375.

The chart clarifies that ARB has analytically divided California into three groups: (1) the “Big Four” urban MPOs, (2) the San Joaquin Valley, and (3) the six smaller MPOs (Butte, Monterey Bay Area, San Luis Obispo, Santa Barbara, Shasta, and Tahoe Basin).

Not much is expected of the six smaller MPOs at this point, since they have limited resources and oversee less populated regions.  For these MPOs, ARB did not propose a distinct target range as it did for the Big Four and the San Joaquin Valley.  Instead, the target will based on current greenhouse gas projections, updated to take into account the effects of the economic recession and any other reductions that may be realized.  This is basically a shortcut — and it’s not unexpected, given that these regions collectively only account for about 5% of vehicle miles traveled (VMT) statewide.  They are also expected to grow slowly.

It’s no surprise that ARB has preferred instead to concentrate its energies on the Big Four — MTC, SCAG, SACOG, and SANDAG — the regions that generate about 87% of VMT.  But beyond meeting greenhouse gas targets, SB 375 is about building better cities.  The Big Four include the majority of California’s largest cities, their established transit networks, and countless infill opportunities to house the state’s future population near transit and employment.  The Big Four have worked collaboratively in this process by modeling different future scenarios and studying how they reduce transportation emissions.  ARB’s 5 to 10% draft target for the Big Four reflects this initial analysis.  The 2035 ranges are taken directly from the MPOs as scenario outputs.  In addition to the 2035 ranges listed in the table, SCAG was the only agency to suggest an actual target for 2035 (5 to 6% reduction).  But as mentioned above, these numbers are too rough to be taken at face value.

And what are we to make of the 1 to 7% reduction target for the San Joaquin Valley?  We might as well just come out and say it.  Nobody really knows what to do about the Valley.  There are opportunities to do good land use planning there, particularly in downtown districts that will be served by high-speed rail.  For instance, Fresno — California’s fifth largest city, with about a half-million residents — was able to project some reductions, by analyzing scenarios that included bus rapid transit and increased density on mixed use corridors.  But other parts of the Valley have projected increases in emissions, which we know we don’t want.  And that is, more or less, the sentiment that is captured in the 1 to 7% reduction target.  A reduction of 1% might not be ambitious, but at least it’s not an increase.  Given the unique challenges in the Valley, more analysis is needed to pin down a suitable target.  I would only note that an anti-sprawl campaign in California cannot be deemed truly successful unless it addresses the rapid, unchecked growth of sprawl  in the Valley.

ARB’s draft targets are basically a consolidation of the collaborative work that the agency has done thus far with California’s MPOs.  But that is not the end of the story.  This summer presents a key opportunity for MPOs to refine their technical work before the fall deadline.  As they do so in the coming weeks, these draft target ranges will ideally be honed into more precise ambitious-yet-achievable targets.



3 thoughts on “ARB releases draft greenhouse gas targets for SB 375

  1. Eric,

    Thank you for covering this issue. I blogged about it on my site at

    I encourage you and your readers to check it out.

    Posted by Juan | 1 July 2010, 1:23 pm


  1. Pingback: Regional HOT lane network going back to the drawing board « Transbay Blog - 8 July 2010

  2. Pingback: Air Resources Board proposes final regional targets for SB 375 « Transbay Blog - 11 August 2010

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