A new study from UCLA’s department of civil and environmental engineering undertakes a life-cycle assessment for HSR. Their conclusion is what we always conclude:
The energy and emission intensities of each mode were normalized per passenger kilometer traveled by using high and low occupancies to illustrate the range in modal environmental performance at potential ridership levels. While high-speed rail has the potential to be the lowest energy consumer and greenhouse gas emitter, appropriate planning and continued investment would be needed to ensure sustained high occupancy. The time to environmental payback is discussed highlighting the ridership conditions where high-speed rail will or will not produce fewer environmental burdens than existing modes. Furthermore, environmental tradeoffs may occur. High-speed rail may lower energy consumption and greenhouse gas emissions per trip but can create more SO2 emissions (given the current electricity mix) leading to environmental acidification and human health issues. The significance of life-cycle inventorying is discussed as well as the potential of increasing occupancy on mass transit modes.
Being the cleanest mode per passenger hinges on getting a critical mass of people using it. The timeframe for payback on emissions invested in the colossal investment: about 70 years. I won’t see it, but my students might.
UC Berkeley’s economics and engineering programs have also weighed in:
“We found that the model that the rail authority relied upon to create average ridership projections was flawed at key decision-making junctures,” said study principal investigator Samer Madanat, director of ITS Berkeley and UC Berkeley professor of civil and environmental engineering. “This means that the forecast of ridership is unlikely to be very close to the ridership that would actually materialize if the system were built. As such, it is not possible to predict whether the proposed high-speed rail system in California will experience healthy profits or severe revenue shortfalls.”
More than that. We do not know whether the benefits we’ve ascribed to the investment will actually materialize.
Perhaps we will be fortunate and the forecast will under-predict? That would be a bit of a coup, as it doesn’t happen very often.
Peter Gordon and I had an online conversation about the nature of the inaccuracies we generally have in transportation forecasts, particularly for entirely new services like intercity HSR. It strikes me that one of the groups that does this well are the freight shippers. They don’t, in general, tell about how they analyze their markets.