February 21, 2023 | Matt Frommer & Grace Hood
Transportation is the largest source of climate emissions in Colorado, and the sector with by far the biggest deficit in meeting the state’s 2025 climate targets — a gap of more than nine million metric tons (MMT) of greenhouse gas (GHG) pollution. Efforts to introduce more electric vehicles (EVs) in the coming years are critical but insufficient on their own to meet our climate goals and avoid the worst impacts of global warming. The state must also embrace more ambitious policies to reduce driving and enable more transit, biking, and walking.
At the same time, Colorado’s in the middle of a severe housing crisis. Our inability to produce enough housing has priced out many essential workers like teachers, nurses, bus drivers, and childcare providers, exacerbating the labor shortage. Many low-income residents are housing cost-burdened and have to choose between paying the monthly rent and affording other basic life necessities like medicine and food. To stabilize the housing market, Colorado needs to double the rate of housing production to 54,000 units per year while also making a concerted effort to build more permanently affordable homes for low-income Coloradans so they can live near where they work.
Solving these problems is mind-numbingly complex, but if you consider them together, an important solution emerges: climate-friendly land use. By allowing housing choices like duplexes, triplexes, fourplexes, and accessory dwelling units in single-family zones and encouraging more compact development near transit stations and job centers, local governments can expand housing opportunities while reducing driving and pollution: a win-win.
Duplexes, triplexes, and fourplexes can increase housing availability while fitting into the existing neighborhood context.
In addition to more housing options, climate-friendly communities promote a mix of land uses in close proximity to one another. Cities around the world have adopted goals to become “15-minute cities,” where basic needs and destinations like grocery stores, pharmacies, parks, schools, and restaurants are within a 15-minute walk or bike ride. Such neighborhoods give residents the option to leave their cars at home. For those who still choose to drive, trips are shorter. Imagine how much pollution we’d save if everyone could reach their jobs and daily errands with 10 miles of driving instead of 22, the current state average.
In this report, we quantify the potential GHG savings associated with climate-friendly land use, examine the relationship between density and driving at the neighborhood level, and highlight a few examples of climate-friendly development in the Denver region.
Cutting GHG emissions with climate-friendly land use
Updating Colorado’s land use policies to focus the majority of the population and job growth in urban areas has the potential to reduce annual GHG emissions from transportation by 1.3 MMT in the next 10 years, the equivalent of taking 280,000 cars off the road.*
These policies also lower emissions from the buildings sector because attached and smaller homes like duplexes and apartments require less energy to heat and cool. If we consider all sectors, including transportation, buildings, upstream vehicle and petroleum emissions, embodied carbon, and avoided natural land conversion, the potential GHG savings from climate-friendly land use could be 2 MMT or more. This is on par with Colorado’s goal of getting 1 million EVs on the road by 2030.
Failing to pursue climate-friendly land use means more of the same low-density, car-dependent sprawl that Colorado has been experiencing for decades. From 1997 to 2009, the Denver region’s designated area for development grew by 40 percent from 700 to 980 square miles. Such unfettered exurban sprawl only leads to more driving emissions, traffic, land and water consumption, and social and economic inequities.
Just add density: The secret to getting cars off the road
Allowing more compact development in urban areas not only means less driving for the families that move there, but it can also reduce driving for existing residents. For the average neighborhood in the Denver region, a 30 percent increase in residential density is associated with a 1,000-mile decrease in annual driving for neighborhood residents. Compact development, even at modest levels, fosters enough density to support a variety of nearby businesses and frequent transit service within walking distance.
Households in Denver’s densest neighborhoods drive less. The colors indicate the percentage of homes in each neighborhood that are single-family, most likely because they’re restricted by zoning. Red dots represent neighborhoods where more than three-quarters of homes are single-family and the average driving per year is 16,200 miles. For the blue dots, between one-quarter and three-quarters of the housing stock is single-family, and the average household drives 14,600 miles annually. Lastly, green dots indicate neighborhoods where less than one-quarter of homes are single-family and the remainder are multiplexes and multifamily apartment buildings. The average driving is around 13,600 miles per year. (Source: Southwest Energy Efficiency Project (SWEEP) analysis using Center for Neighborhood Technology data for the Denver-Aurora-Lakewood Metropolitan Statistical Area. Graphic inspired by Sightline Institute.)
Every year, hundreds of homeowners in Denver scrape older single-family homes and replace them with larger single-family homes — the only housing type allowed on over 70 percent of residential lands. If just a handful of the 30 homes around the average Denver city block were converted to duplexes, triplexes, or fourplexes instead of new single-family McMansions, the neighborhood would cross the “15-minute city” density threshold and be able to support local businesses and frequent transit.
What does climate-friendly land use look like in Colorado?
It could look similar to Belmar in Lakewood. In the early 2000s, the City of Lakewood decided to redevelop the land where the old Via Italia Mall was located. A citizens advisory board helped to guide the vision for what today is a 22-block commercial and residential area with a mix of restaurants, homes, shops, and businesses.
Belmar Square Park is ringed by condos and apartments.
More than 2,000 people live within the redeveloped areas, mostly in duplexes, triplexes, townhomes, and condos. Another 4,000 nearby residents can walk to the shops and restaurants. Average daily driving for Belmar residents is just 18 miles per capita, 20 percent below the regional average, making it one of the greenest neighborhoods in Lakewood (see the green square below).
New York Times map of greenhouse gases per household and Walk Score.
Belmar is considered a “Walker’s Paradise” because it offers easy access to restaurants, coffee shops, grocery shopping, parks, schools, and entertainment within a five-minute walk. As a result, Belmar households are more likely to own one car instead of two, which helps families save money on car expenses and leads to less worrying about gas prices.
In addition to less pollution, climate-friendly land use also helps to conserve water at a time when the Colorado River, the lifeblood of the West, is drying up. In Denver, the typical single-family home uses twice as much water as multi-unit dwellings, primarily because of their larger and more thirsty lawns. Allowing duplexes, triplexes, fourplexes, and multifamily buildings in districts currently restricted to single-detached units could result in as much as a 30 percent reduction in outdoor water use.
Climate-friendly land use is transit-oriented
Public transit is a critical strategy for reducing vehicle trips and air pollution, but unleashing its full climate potential requires Transit-Oriented Development (TOD). To put this in perspective — Denver’s regional transit agency, the Regional Transportation District (RTD), is responsible for cutting about 192,000 metric tons (MT) of GHG pollution every year by replacing car trips with bus and train trips. An impressive number, but it pales in comparison to the 793,000 MT in GHG savings from “land use efficiency” around RTD’s transit stations (see the green bars in the graph below). Well-planned transit systems cluster housing and jobs around the stations. Even the residents who don’t take transit will drive less because their neighborhoods are more walkable and bikeable.
When it comes to TOD, building the “T” without the “D” leaves 80 percent of the GHG savings on the table.
The Federal Transit Administration’s Transit Cooperative Research Program
Shining examples of successful TOD in Denver, present and future
Travel northeast to RTD’s light rail station at 10th and Osage, and you’ll find a transit station horseshoed by mid-sized apartment buildings, most of them reserved for permanently affordable housing.
The station is busy with the 10th highest ridership on RTD’s light rail system. Within an eighth-of-a-mile radius of the station, there are over 450 affordable homes and nearly 130,000 square feet of commercial space recently built out. More than 1,200 additional homes, around 20 percent of which will be affordable to low-income families, are slated for construction within a half-mile radius, many of them on the business corridor of Santa Fe Drive (more bonus points for mixed-use development!).
All this transit opens the door to a lifestyle that is less car-dependent. The average resident in the zip code drives just 14 miles per week, nearly 40 percent below the regional average. Residents are three times more likely to use transit or walk to work than the average Denver metro resident. Fewer cars could eventually translate into downstream impacts like less gasoline being refined and consumed–and ultimately less oil and gas extracted from the ground.
Lone Tree’s new city on the plains
Enabling infill development inside the existing urban area is absolutely necessary if we hope to grow sustainability, but Lone Tree is showing that we can also grow responsibly on the plains around the urban edge. Lone Tree is making the most of its investment in RTD’s light rail expansion by planning dense, mixed-use communities around its new transit stations. Construction is now underway on affordable housing, senior living, offices, and a commercial area at RidgeGate Station.
The Lone Tree City Center Sub Area Plan shows the planned transit-oriented development around the RTD City Center and RidgeGate stations.
As you move closer to the light rail stations, the zoning allows building heights to gradually increase from single-family homes to duplexes, triplexes, and fourplexes, and then taller 5-10 story apartment and office buildings. Of the 700 new homes planned for Ridgegate Station, half will be affordable to low-income households.
RidgeGate will also have walkability and bikeability like Belmar and 10th and Osage Station — reducing car dependence for new residents. The estimated 5,000 new residents will have a new grocery store within walking distance, helping to limit the number of car trips. According to the city plan, designers specifically considered how easy it would be to navigate the development on foot with an ideal grid of block sizes for walkability.
Climate-friendly land use supports the preservation of open space, another important feature of RidgeGate Station. The downtown residential area is zoned for 1,620 homes on 54 acres of land, an average of 30 units per acre. If we consider a likely alternative, where we spread the same number of homes over the average single-family zoning density of 4 units per acre, the development would consume seven times more land, over 400 acres, and much more water for irrigation.
Source: Design Workshop
Transit-oriented development must be equitable: Expanding affordable housing and preventing involuntary displacement
Colorado’s extreme housing deficit hurts low-income families the most. When there’s a shortage of market-rate homes, middle-income families are forced to compete and bid up the price of homes that would otherwise be affordable to low-income households, shrinking the pie. As a result, for every 100 extremely low-income households in Colorado, there are only 30 adequate, affordable, and available rental units. Solving this requires both an increase in total housing production to take pressure off the lower-income markets and targeted investment in deed-restricted affordable homes for low-income families.
Many local governments have taken important steps to increase the number of permanently affordable units — strategies like Inclusionary Zoning Ordinances, which require developers to either build a minimum number of affordable homes in multifamily buildings or pay into an affordable housing fund. Around 20 cities and counties in Colorado have these ordinances in place, with more than half adopted in the last few years.
Without specific protections and guardrails, the influx of capital investment around transit stations has the potential to accelerate the involuntary displacement of vulnerable residents and businesses. Local governments like the City and County of Denver have tackled this head-on by creating innovative anti-displacement programs like rental assistance and housing prioritization policies for its most vulnerable residents. Such programs should be scaled up and replicated to preserve neighborhood stability and ensure that current residents benefit from transformative investments in housing, transit, parks, and other amenities instead of getting driven out by high prices and redevelopment pressures.
The combination of affordable housing and rapid transit, known as Equitable Transit-Oriented Development, hits the sweet spot for both climate and equity. From an affordability perspective, the economies of scale offered by larger multifamily projects give non-profits and developers an opportunity to deliver more deeply affordable units for low-income families. In addition, providing easy and convenient access to clean and low-cost transportation options like transit, biking, and walking saves money and improves job access for people who need it most while also cutting pollution and fostering healthier and more active lifestyles.
Completing the second half of the TOD equation
For every example of a Denver transit station with good TOD, there are three that aren’t fulfilling their potential. A quick zoom around Google Earth shows dozens of light rail stations surrounded by vacant land, industrial buildings, highways, and massive empty parking lots — essentially the anti-TOD.
As a result, RTD’s system is underutilized and inefficient compared to peer transit agencies. Across 10 peer cities in the western United States, RTD’s 2019 rail service delivered the fewest trips per service mile, a common metric of transit system efficiency and cost-effectiveness. Trains in Portland, Seattle, Minneapolis, and Phoenix are more than twice as full. The COVID-19 pandemic and the sustained shift to telework have only made the problem worse and current ridership is about 60 percent of pre-pandemic levels.
Over the last 20 years, the Denver region has invested $6 billion to build nearly 80 miles of new FasTracks rail service. Many of the new stations were designed for commuters with big Park-n-Ride lots surrounding them. By now it’s clear that many of those former riders are not going to return to the office. To make this historic transit investment worthwhile and bring back ridership, we need to adjust our land use plans and build more TOD around RTD’s system.
For many transit station areas, the combination of restrictive zoning, lack of infrastructure, excessive parking mandates, and other local regulations are preventing new development. Completing the TOD vision requires a collaborative effort to identify and remove these barriers. First, cities need to update their zoning regulations to allow more housing around transit stations. Just as importantly, cities should develop policies and programs to produce more affordable housing and prevent involuntary displacement.
To address infrastructure needs, state and local governments should revise transportation planning guidelines to direct more funding to TOD infrastructure, including the road, bicycle, and pedestrian facilities around the transit stations. Supporting TOD aligns with the Colorado Department of Transportation’s adopted goals to reduce vehicle trips, alleviate congestion, eliminate traffic fatalities, and cut GHG emissions.
Lastly, most cities in Colorado have costly parking mandates that require new buildings to overbuild their parking. According to RTD’s 2020 Parking Study, about half of the parking spaces around their transit stations sit empty, even during peak periods. Parking mandates increase housing costs — $25,000 to $50,000 per new parking space increases the average rent by $225 per month — and dedicate valuable space to car storage instead of housing.
As a result, cities like Denver have taken steps to eliminate parking mandates downtown and for new affordable housing near transit. To be clear, removing parking mandates does not eliminate all new parking. Rather it gives local businesses and builders the opportunity to right-size their parking to meet market demand, share parking with their neighbors, and fit into the neighborhood context. For example, for new apartment buildings in downtown Denver, about half provided more than the standard one parking space per home while the other half provided anywhere between 0.39 and 0.94 spaces per home, and in turn, were able to dedicate more investment and land to housing. Cities should go one step further and scrap parking mandates throughout the city to maximize land efficiency and lower the cost of development.
This is a pivotal moment in Colorado’s history where we need to decide how we want to grow in the future. It’s high time for policymakers to recognize that climate-friendly land use is an important lever to tackle transportation pollution and our housing affordability crisis. Updating land use policies to allow more housing choices, support affordable housing and mixed-use development near transit and jobs, and prevent sprawling development on open space will result in more sustainable, healthier, and equitable communities.
*Notes of methodology
To calculate the estimated GHG reductions from climate-friendly land use policies, SWEEP worked with our colleagues at the Rocky Mountain Institute and Replica’s modeled data about activity in the built environment. The analysis assumes Colorado updates its land use policies and produces enough housing to close the 175,000-unit deficit and keep pace with population growth. The result is 554,000 new homes by 2032. We assume 90 percent of the new homes will be located in the most transportation-efficient areas where residents drive 14 miles per day, 37% less than the current state average. The result is a 6.3 percent reduction in statewide VMT by 2032 and a 1.3 MMT reduction in GHG emissions from light-duty vehicles.
This is a simple estimate, not intended to substitute for specific modeling of real land use policy reform proposals. It can be considered optimistic in assuming policy can fully solve the housing shortage in ten years, without facing constraints such as the ability of the construction industry to respond, while directing most new housing to transportation-efficient areas. It can also be considered conservative in assuming no transportation synergies with existing housing, such as improved transit and access to retail for people currently living in areas where new housing is added.