Transportation's Role in Reducing U.S. Greenhouse Gas Emissions ...

Transportation’s Role in Reducing U.S. Greenhouse Gas Emissions: Volume 2
additional VMT results in additional fuel consumption and GHG emissions; it also
reduces the initial travel speed and traffic flow benefits of these strategies. The magnitude
of the induced demand is subject to considerable uncertainty, as is its impact on delay
reductions and fuel savings. Bottleneck relief projects also involve GHG emissions from
construction activities and delay during construction, which further offset any GHG
reductions, although these effects have also not been rigorously analyzed.
The Moving Cooler study estimated that, not considering induced demand effects or
construction emissions, improving the top 100 bottleneck locations in the country could
reduce GHG emissions by 6 mmt CO 2e in 2030, while improving the top 200 locations
could reduce emissions by 14 mmt (Cambridge Systematics, 2009). 22 The benefits of
bottleneck improvements, however, may be substantially reduced through induced
demand effects, as more travel occurs in response to improved highway conditions (see
Appendix A). Using assumptions consistent with FHWA’s 2008 Conditions and
Performance Report (FHWA, 2008d), the Moving Cooler study estimated that the GHG
benefits of bottleneck relief would be reduced to 1 to 6 mmt CO 2e in 2030 if induced
demand effects were included; 23 this analysis assumed (consistent with the Conditions and
Performance Report methodology and current highway funding practice) that projects
would be fully financed by increased fuel taxes, which would partly dampen the induced
demand from lower congestion levels. The study further concluded that as increased
travel outweighed the efficiency gains in later years, the entire cumulative GHG
reductions from bottleneck improvements over the 2010 to 2050 period could potentially
be offset by induced demand (Cambridge Systematics, 2009).
Cost-Effectiveness
The costs of individual bottleneck relief projects vary widely, but typically range on the
order of a few million dollars on the low end, to tens—or even hundreds – of million
dollars for construction projects such as interchange construction/reconstruction or lane
additions on short segments. Improving the top 100 bottleneck locations in the country is
estimated to cost $28.8 billion, or about $280 million per location (AHUA, 2004). Since
these are the locations where delay is greatest, they also are locations where investment
costs are likely to be greatest. Not including induced demand effects, the Moving Cooler
study estimated the cost per tonne of GHG reduction of improving the top 100 bottleneck
locations in the country to be $90 per tonne GHG, or $130 per tonne for the top 200
bottlenecks, considering direct costs alone. If vehicle operating-cost savings are taken into
22
Bottlenecks were identified based on a study for the American Highway Users Alliance (AHUA,
2004) and were defined in this study as a “severe traffic chokepoint” at which drivers spend at
least 700,000 hours per year in congestion. Most of these bottlenecks are single interchanges
(usually freeway-to-freeway), a series of closely spaced interchanges, or lane drops on freeways.
23
As described in Footnote 12, the travel demand impacts (including induced demand) were
calculated using FHWA’s HERS model, which estimates demand as a function of total user costs,
with a short-term elasticity (first five years) of roughly -0.4 and a long-term elasticity of roughly -
0.8.
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