By Kevin McDonald
The limited-access highway has deemed by planners, environmentalists and much of the public at-large to be an unsustainable urban form of transportation. The unsustainability is driven by three elements of this facility: 1) non-renewable gasoline to power automobiles that use the highway, 2) the noise, disruption and pollution created by the automobile’s engine and operations, 3) energy-intensive forms of the built environment. These key issues are juxtaposed against the indelible strength of the limited-access highway: point-to-point transportation that efficiently and quickly delivers goods and people. In the US, those arguing against the sustainability of the urban freeway appear to have the day- the country has only added 2% to its 1980 levels of urban mileage. Recent technology innovations have mitigated the negative externalities of the urban freeway. This begs the question: is it time to rethink opposition to new investments in urban highway lane miles?
As automobiles become more fuel efficient (or solely use electricity, such as cars from Tesla Motors), the unsustainability of the automobile falls away. The USDOT currently estimates cars use 3,500 BTUs per passenger mile, buses use 4,242, while light-rail uses roughly 2,500. So while these figures suggest light rail is the most environmentally advantageous, increasing efficiency of the gasoline engine will blur these differences to the point where the marginal energy use by mode will be almost indistinguishable. Indeed, cars like Chevrolet Volt are already more sustainable per BTU mile than the average city bus or commuter rail system. In future, suburban commuters may not be using much fuel for transportation, regardless of the source.
Pollution, noise and land-clearings are also suggested as an unsustainable and indelible part of urban freeway construction. The changing propulsion methods for automobiles will reduce the pollution and noise from cars to the point where AASHTO has required new zero-emissions electric cars to emit a noise so pedestrians hear their presence. Plug-in hybrids like the Volt and Prius PHV are providing clean, quiet urban transportation. Highways like Connecticut Route 11 Greenway and roads that utilize existing industrial and transportation corridors do not result in 1960s style urban neighborhood demolition that still scars our psyche.
Urban sprawl induced by freeways is also a key problem, but there are ways to reduce the induced demand of diffuse housing that require enormous amounts of energy, water and investment. Along the NYS Thruway, there are seventeen miles of flat, developable land in Rockland County amidst the wealthiest region in the nation. The key to the lack of development is the lack of exits from the freeway. By restricting the number of exits and when available, requiring strict land use rules and ramp tolls, a limited-access freeway can allow for easy access of land for dense, urban style development and act as a release valve for urban areas with strict land use controls that increase commercial and residential rents, that deters healthy growth.
Given that transit on average requires at least one transfer, trips take twice as long as those in an automobile and in the face of new transportation innovation, we might need to ask whether it’s time to rethink the urban freeway.