April 22, 2021

Sustainability + Transportation

Noah Hagen contributed to this article.


Due to rising concerns about climate change over the past several years, environmental sustainability has become a major consideration in almost every transportation project today.  Developers, engineers, architects, and planners hold greater responsibility to commit to creating a built environment that reduces negative environmental impacts.

In that effort, transportation engineers and planners usually seek to limit the number of single-occupancy vehicle trips to a given site and in the city as a whole.  They typically accomplish this by providing connectivity to public transportation and creating safe and comfortable spaces for pedestrian and cyclists to travel.  Locally, DC’s Department of Energy & Environment affirms that “shifting our transportation system away from single occupancy vehicle trips towards walking, biking and using public transit is the best way to reduce our energy use in the transportation sector.”

In 2018, the Transportation sector accounted for 28% of United States Greenhouse Gas Emissions.  Breaking down the contributions within transportation, Light-Duty Vehicles are the source for 59% of emissions.  The EPA reports that “a typical passenger vehicle emits about 4.6 metric tons of carbon dioxide per year,” and producing and distributing the fuel to power vehicles creates additional greenhouse gases.

The transportation shift toward non-auto modes is met with several challenges including funding, , and accessibility. The first hurdle for many individuals is overcoming a reliance on automobiles as a primary mode of transportation. Transportation Statistics Annual Report 2020 found “households increasingly own more vehicles, with two- and three-vehicle households now comprising a larger share of the population than o.” One way that planners seek to reduce the number of single vehicle trips is through eliminating the mandatory vehicle parking requirements that most cities impose on new developments.  An article from Bloomberg CityLab links cheap, excessive parking to drive-alone commutes, traffic congestion, and higher rents.  To combat this, some cities are moving towards repealing mandatory parking requirements.

In Buffalo, the 2017 Green Code repealed all mandatory parking requirements (MPRs) in the city.  In the years since it was enacted, “mixed-use developments in transit-rich locations along primary commercial corridors tended to provide fewer off-street parking spaces relative to preceding MPRs.”

Lifting parking requirements creates flexibility for addressing transportation needs. As opposed to minimums, DDOT recommends “preferred” parking maximums as part of the Comprehensive Transportation Review guidelines that large developments need to meet before gaining approval.  Put simply, they argue that “if you plan and design for auto-oriented development, you’ll get high traffic generating development.”  The maximums depend on building size, use, and proximity to transit.  Buildings that have too much parking are required to provide additional Transportation Demand Management measures to reduce vehicle trips to the site.

In instances where parking is reduced, fewer people would be driving, likely utilizing alternative modes of transportation, lowering emissions, and moving towards more sustainable transportation.

A great alternative mode of transportation with zero emissions is the bicycle.  Bicycles promote not only sustainability but also personal health and fitness.  Many people turned to bicycles in the last year as an alternative to using public transportation during the COVID-19 pandemic.

A New York Times article from May 2020 reported, “the spike in sales comes on the heels of stay-at-home orders that have temporarily curtailed daily life, but that may permanently transform the role of bicycles into something more essential, including a safer alternative to public transit as the nation slowly begins to reopen.”

As more people took to cycling, cities responded with initiatives like DDOT’s Slow Streets and Car Free Lanes.  Providing additional space for cyclists to move about the city safely might give reassurance to some still on the fence about trying cycling.  While these things came about as a result of the pandemic, if they become permanent fixtures, the number of cyclists may continue to grow or at least hold steady at what’s been reported during the pandemic.

The same New York Times article cites Sarah M. Kaufman, Associate Director of New York University’s Rudin Center for Transportation Policy and Management, saying “The U.S. has been built around cars. The European model has tended to be more forward looking in terms of sustainability and safety, which leads them to favor bikes.”

We have seen DC, Arlington and other jurisdictions adopt Vision Zero plans in an effort to improve safety for cyclists and pedestrians.  Vision Zero positions itself as “a fundamentally different way to approach traffic safety,” seeking to “eliminate all traffic fatalities and severe injuries, while increasing safe, healthy, equitable mobility for all.”

Moving commutes and local errand runs from trips made in vehicles to bicycles will help to cut down tailpipe emissions. Another option is shifting towards utilizing public transportation.  The significant advantage to public transportation is the increase in passengers per trip using the mode of transportation.  While a bus may produce more CO2 emissions than a vehicle, the bus can accommodate more passengers than a single car and thereby reduce the number of vehicles on the road concurrently.

Public transportation has also committed to improving sustainability efforts.  The District’s public bus system, the Circulator, includes 14 fully electric vehicles in their fleet (DC Department of Energy & Environment).  Washington Metropolitan Area Transit Authority (Metro) has committed to planning for a zero-emission fleet in their 2019 Energy Action Plan.

Parking, bicycling paths, pedestrian friendly spaces, and public transportation are all key considerations in creating and implementing Transportation Demand Management plans. TDM plans are created for buildings or developments to provide occupants with a comprehensive menu of transportation options for that area.  The strategy considers bike and pedestrian choices, public transportation connectivity, carpooling, and telework programs to give users a range of transportation options.  Providing these alternative modes of transportation may influence a move away from reliance on automobile trips to travel to/from the destination.

With updated guidelines and regulations coming from jurisdictions coupled with transportation demand management plans, transportation engineers and planners will continue to work in tandem with clients, developers, and governing bodies to move towards more sustainable transportation for the community.



DC’s Department of Energy & Environment

EPA Greenhouse Gas Emissions

EPA Fast Facts Transportation

Transportation Statistics Annual Report 2020

Bloomberg CityLab

SideWalkTalk Buffalo Ended Parking Requirements

DDOT Guidance for Comprehensive Transportation Review in the District of Columbia

New York Times, Coronavirus Bike Shortage

Vision Zero Network

WMATA Sustainability