The pandemic helped Houston move up on the list of greenest cities


Shifts in travel habits because of the pandemic, including less driving and more active transportation, drove the metro’s improved ranking among the most climate-friendly areas in the U.S.

Shifts in travel habits because of the pandemic, including less driving and more active transportation, drove the metro’s improved ranking among the most climate-friendly areas in the U.S.

The pandemic upended every aspect of American life in 2020, from how and where we work and go to school, to how and where we spend our free time and socially interact with friends and family. For many reasons, including working from home, pandemic-related job losses, stay-at-home orders, remote learning and efforts to limit travel to essential trips, Americans drove far less than normal.

Compared to 2019, all 80 of the largest U.S. cities experienced less traffic in 2020 — from 10% to as much as 47% less. Congestion levels fell as well, from 2% to as much as 15%. Houston saw 33% less traffic and the congestion level dropped from 24% to 16% last year. Who would’ve thought they’d see the day Boise had worse congestion than Houston? It was that strange of a year.

Transportation is the number one cause of carbon emissions in the United States (28%), and vehicles driven in cities and suburbs account for the largest share of those emissions, which include automobiles and airplane flights. While Americans spent less time in their car or commuting, they spent a lot more time exploring their neighborhoods and cities on bikes and on foot. Because of this and the reduction in vehicles miles traveled (VMT), the ranking of “greenest cities” in the U.S. was another thing upended in 2020.

According to the U.S. Transportation Climate Impact Index, the ranking of the “greenest” or most climate-friendly metropolitan areas in terms of transportation in 2020 looked a lot different compared to 2019. Using location-based services data from mobile phones, Streetlight Data ranked the 100 most populous metropolitan areas on six factors: vehicle miles traveled (VMT), biking and walking, transit ridership, density and circuity (the difference between an actual route taken and a straight line between A and B). Each of the factors was weighted relative to its impact on transportation greenhouse gas emissions. VMT, the most important factor in the index, was weighted much heavier than the other five.

Houston, Phoenix and Dallas — big, sprawling Sun Belt metros — were ranked the three worst metros in the nation at Nos. 98, 99 and 100, respectively, according to the 2019 Transportation Climate Impact Index. A year later, Houston moved up to No. 71 and Phoenix jumped 77 spots to No. 22. Dallas gained a modest amount of ground, moving to No. 90.

Other Sun Belt metros made big moves in the rankings as well. San Diego had the largest jump of all, from the seventh worst to the eighth best. Miami moved from No. 67 to the top 10, at No. 6, and Tampa went from 81st to 25th.

In 2019, commuters in Texas had the worst impact on the climate of all states. (The state leads the nation in the total amount of CO2 emissions from fossil fuel combustion, producing 245 million metric tons from transportation, 349 million metric tons from industrial and 201 million metric tons from electrical power plants in 2018.)

Here are the 2019 and 2020 Transportation Climate Impact Index rankings for large Texas metros:

Texas metros 2019 ranking 2020 ranking
Austin-Round Rock No. 61 No. 32
McAllen-Edinburg-Mission No. 44 No. 36
El Paso No. 69 No. 44
Houston-The Woodlands-Sugar Land No. 98 No. 71
San Antonio-New Braunfels No. 83 No. 82
Dallas-Fort Worth-Arlington No. 100 No. 90

The rankings for the Houston metro area in 2019 and 2020:

VMT Bike Ped Transit Density Circuity Overall ranking
2019 99 43 48 36 20 7 98
2020 81 45 37 30 20 57 71

The Houston metro’s overall improvement was mostly due to an improved ranking for VMT — from second worst in 2019 to No. 81 — but biking and pedestrian activity increased as well. So did the metro’s transit ranking — moving from No. 36 to No. 30 — despite the brutal toll the pandemic took on Metro ridership last year. (Note: While Metro’s ridership has no doubt declined significantly since the pandemic began, it leveled off in July and has held steady since. This indicates a core group of riders — many of whom most likely are essential workers who can’t work from home — continue to use and remain reliant on transit.

Some metros grew greener, others wilted

The New York metro area held the top spot for the second year in a row. There were three Florida metros in the top 10, and five in the top 25. North Port-Sarasota-Bradenton was No. 2 overall, thanks to the strength of residents’ biking activity (No. 1) and pedestrian travel (No. 4), as well as reduced VMT. Cape Coral-Ft Myers also rode the index’s bicycle and pedestrian travel per capita metrics to a high ranking at No. 4. Unlike those two Florida metros, which were both in the top 20 in 2019, Miami-Fort Lauderdale-West Palm Beach saw a significant improvement in its climate-impact friendliness in 2020, going from No. 67 to No. 6. Miami’s improvement was due to the big drop in driving in 2020, going from No. 90 in 2019 to No. 3 in the VMT ranking.

An improved VMT ranking also fueled San Diego’s impressive rise, though its biking and walking rankings were higher as well. Other metros that experienced dramatic changes (for the better) in the rankings were Colorado Springs, Grand Rapids, Minneapolis-St. Paul, Boise City, Rochester and Wichita. Of course, some metros fell in the ranking between 2019 and 2020, some more sharply than others, including Harrisburg, Pennsylvania (No. 15 to No. 84), New Haven (No. 9 to No. 65), Madison, Wisconsin (No. 3 to No. 68) and Greensboro, North Carolina (No. 19 to No. 96). All of these precipitous falls overall were paralleled by big drops in VMT ranking.

The Streetlight Data analysis revealed three key takeaways from 2020:

Driving and economic growth aren’t connected: While VMT dropped to unprecedented lows in 2020, GDP didn’t follow suit, suggesting that decoupling VMT and GDP is possible.

“Active transportation” plays a larger role: Although cycling activity increased in many areas, it actually dropped in many major cities – most notably in cities with a history of very active bike commuting. This isn’t surprising for a year with widespread work-from-home mandates. Our analysis found that even in those cities, bicycling did not drop as much as driving. This indicates that bike riding took up a larger share of total miles traveled in 2020.

Work-from-home isn’t a silver bullet: Although widespread work-from-home policies were still in place at the end of 2020, the fall in commuting did not translate to permanent or drastically lower amounts of driving. In fact, by August, VMT had begun to climb back to pre-pandemic levels, albeit with peak traffic spread over more hours during the day.

Last month, the Rhodium Group reported that, because of the pandemic, greenhouse gas emissions in the U.S. were reduced by 10% in 2020. The reduction puts GHG emissions below 1990 levels and is the biggest drop since World War II. Compared to 2005 emission levels, last year’s reduction represents a 21.5% decrease in emissions.

“The emission reductions of 2020,” the report points out, “have come with an enormous toll of significant economic damage and human suffering.”


“With coronavirus vaccines now in distribution, we expect economic activity to pick up again in 2021, but without meaningful structural changes in the carbon intensity of the US economy, emissions will likely rise again as well.”

For example, if companies permanently adopted a one-day-a-week work-from-home policy, the commute VMT of their employees could be lowered by 20%, Streetlight Data analysts estimate.

After a year as terrible and eye-opening as 2020, we’re at a decisive moment in history. What will we choose to do to address the problems of racial injustice, widespread disparities and climate change? As for that last one, COVID-19 forced unprecedented shifts in how we work, travel, eat out, shop and share public spaces, all of which changed traffic in unprecedented ways. If we embrace some of those shifts, maybe we can make the unprecedented into permanent.

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