As cities become more crowded, space utilization and efficiency for transportation become critical to the quality and effectiveness of the transportation network. Improving travel efficiency is also essential for achieving other goals, such as reducing greenhouse gas (GHG) emissions and managing delay or travel time reliability. Traditional measures of transportation network performance do not provide a complete picture of travel efficiency and have contributed to the land use and transportation decisions in the U.S. that have caused substantial reliance on private automobiles with low levels of vehicle occupancy, or seat utilization. This reliance is difficult to change even in California, where state goals for GHG reduction have not translated to lower levels of driving or emissions as revealed in the chart to the right from the recent 2018 Progress Report California’s Sustainable Communities and Climate Protection Act, California Air Resources Board, November 2018.
Uber proposed a new travel efficiency metric.
To change current outcomes, transportation analysis practice would benefit from new metrics measuring efficiency and space utilization directly. The travel efficiency metric proposed by Uber, person miles traveled divided by vehicle miles traveled (PMT/VMT), is a useful example because it can be measured across all passenger modes and can be adapted for freight travel too. Its connection to carbon intensity (carbon emissions/PMT) has similar benefits. Adding these metrics to the planning process would improve the understanding of whether land use and transportation network decisions are creating more travel-efficient and climate-sensitive outcomes.
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