Mineta Transportation Institute (MTI)

CA: Research Investigates How to Reduce Greenhouse Gas Emissions from Transportation

Greenhouse gas (GHG) emissions must be reduced by 50-80 percent by 2050 to limit a global temperature increase of 2 degrees Celsius (or 3.6 degrees Fahrenheit).  With vehicles as one of the prime producers, how can the transportation sector address that hurdle?

The Mineta National Transit Research Consortium (MNTRC) has just published the peer-reviewed Transportation Futures: Policy Scenarios for Achieving Greenhouse Gas Reduction Targets, which analyzes three possible scenarios. Authored by Andrew I. Kay, MCRP; Robert B. Noland, PhD; and Caroline J. Rodier, PhD, the report is available at no charge and no registration.

“It’s generally accepted that these temperature changes can negatively affect global food supplies, biological health, water quality, and other necessities of life,” said Kay. “Achieving GHG reductions of this magnitude in the transportation sector is a challenge and requires a multitude of policies and technology options. In particular, medium- and heavy-duty vehicles require additional fuel or technology-based GHG reductions. While existing and upcoming regulations deliver certain benefits, it is unlikely that they will be sufficient to meet the GHG reduction goals.”

The research presented in the report analyzes three policy scenarios: changes in the perceived price of travel, land-use intensification, and increases in transit. To forecast the changes from these scenarios, the California activity-based travel demand model was used. This is a statewide model that covers all the regions of California, but they also reasonably represent the US. From this model a variety of travel-demand elasticity estimates were derived for each policy option. These were then applied to forecasts of future vehicle miles of travel from the VISION model while also accounting for potential error bands inherent in the modeling process.

The research results provide useful information for understanding the effectiveness of alternative policies and any additional regulatory policies that might be necessary to close the gap. Of the three travel demand management policies analyzed, only the pricing policy comes close to achieving the 50 percent emission reduction target over the period from 2000-2040, and this assumes a two-fold increase in the price of driving and the highest range of elasticity estimates from the model. Transit and land-use policies provide only minor reductions in emissions. Overall, this analysis suggests that reductions of about 20-40 percent – in addition to those provided through demand management strategies – may be necessary to meet aggressive mitigation goals.

Medium- and heavy-duty vehicles, primarily freight traffic, achieve only small reductions in emissions even with the pricing scenarios. Transit and land-use policies would have little effect on freight emissions. This suggests that further technological improvements far beyond current regulations will be required to reduce emissions from these vehicles.

“These results are consistent with other gap analyses that have been conducted,” said Rodier. “Most studies conclude that aggressive technology policies and reductions in travel demand are necessary to achieve large reductions in transportation GHG emissions. This study reveals a potential gap, particularly in emissions from medium- and heavy-duty trucks, without further regulatory action. The need to increase the price of travel to reduce demand is also critical if the transportation sector is to contribute to global efforts to help stabilize temperatures.”

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