Top posts of 2018: Most efforts to control traffic don’t work. Here are four things that do.

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Whether it’s an apartment building, shopping center, or a mixed-use project, ostensibly well-intentioned residents regularly cite worsening traffic as the reason to stop new development. However, the most common methods communities push for to alleviate congestion make it worse, while the things that actually help usually face strong pushback.

When residents balk at a new development in suburban areas, in most cases a compromise is made: so long as the developer builds “road improvements” or other transportation-related amenities in an effort to solve the traffic problem, the project can move forward.

Yet almost every time, despite those transportation “improvements” and publicly-funded projects, there is still traffic congestion. Seeing this pattern made me wonder: is there a way to actually solve traffic congestion? If so, what really works?

Where does traffic even come from?

In the most basic sense, traffic congestion occurs when the number of motor vehicles on a road exceeds the physical capacity of that road. When there are too many cars, motorists must slow down to avoid crashing, and eventually stop. When there are too many cars, there’s not enough room to get back up to full speed before having to stop again.

Traffic comes from people doing things and going places — in that sense, traffic is a good thing. Businesses want more patrons, museums and parks want more visitors, people want to spend time with their friends and family. These are all hallmarks of a successful, vibrant place.

When a place's activity generates more vehicles than roads can accommodate, traffic congestion occurs. It’s possible to stop traffic by stopping all activity, but this method is analogous to moving to the middle of a desert. There would be no traffic, but not much of anything else, either. Activity is what comprises the “quality” in “quality of life.”

This is the rub with opposing development projects: residents usually want shops, parks, and restaurants, but don’t want the traffic that comes with them. There isn’t room to accommodate amenities along with no traffic congestion.

Why we can’t make nice places with no traffic

Since it’s not popular to tell people they can’t drive, building more space for cars is the usual compromise. Road improvements like widened roadways, new left-turn lanes, or new traffic signals are all designed to increase the capacity of roads. However, this isn’t actually a solution because of a phenomenon called “induced demand.”

Induced demand is the idea that increasing the capacity of a roadway encourages more and more people to use that roadway until eventually the traffic congestion returns. This is better explained here, here, and here. Several decades ago, MD-214 in Prince George’s County, which leads into Washington, used to be two lanes. It’s now six lanes and it still has problems with congestion.

Building more roads to address congestion not only makes traffic worse, it actually makes everything else worse too. Here’s why.

• Encourages more driving: Expanding roadways creates substantial barriers to people who are not driving. A driving-only approach discourages people from walking, bicycling, or taking transit, which leaves only driving as a viable option thus perpetuating traffic congestion.
• Cost: Roads are expensive to build and costly to maintain over time. Gas taxes contribute to these costs but they're usually not sufficient, so road-building costs further constrain local budgets.
• Space: Roads take up lots of space. In a jurisdiction with limited land, every square foot matters. If land in a city is dedicated to cars, then it’s not dedicated to housing, parks, or other more productive uses.
• Safety hazard: Increasing the vehicle capacity of a road tends to decrease safety for people who are not driving. Walking across six lanes of traffic is less safe than walking across two lanes. Walking to a bus stop on a road with vehicles traveling 50 mph is less safe than walking along a road with vehicles traveling 20 mph.

Quite simply, we can’t solve traffic congestion by trying to build more roads for vehicles.

Is there any hope?

Some claim that Autonomous Vehicles (AVs) are going to solve all congestion issues. If AVs do end up achieving everything that they are set out to do, they will certainly improve the situation, but still won’t be able to solve traffic congestion entirely.

Even if AVs can drive closer together, remove the need for traffic lights, and maximize a road’s capacity, they will still take up physical space. At some point, the number of vehicles that can smoothly travel through an area will take up more space than what is available, resulting in vehicles that slow down or even stop.

This leaves one option: reduce the number of vehicles.

People in the US have grown accustomed to using cars even when there are alternatives, so taking them away would be unpopular to say the least. But sometimes, a person who initially drove now chooses to take transit, walk, or bike because it became convenient or affordable to do so. (In transportation planning-speak, this is referred to as “mode-shift.”) This is ideal, but not easily accomplished.

Another approach is to limit the number of new vehicle trips by encouraging people who have just moved to an area to take transit, walk, or bike from the very beginning. This way, cities can continue to develop and generate “activity” without introducing new traffic. Sometimes longtime residents who usually drive are encouraged to switch modes as well.

There are a few ways to accomplish this. The challenge is, most of them are counter-intuitive.

1. Improve transit, walking, and bicycling infrastructure: If every major road had wide sidewalks, marked crosswalks with enough time to cross the street, separated bicycle lanes, accessible transit stops, and bus-only lanes, it would be significantly more convenient to take transit, walk, or bicycle, especially for shorter trips. People are less likely to drive if high quality and convenient alternatives exist.

This may be difficult to envision because there have been decades of automobile-oriented development. Often, community members opposing new development on the grounds of traffic are aghast at the idea of dedicating motor vehicle lanes for anything other than cars. However, improving transit, walking, and bicycling conditions on the road encourages people to use those modes instead, thereby reducing the number of cars and improving traffic.

2. Toll roads: Toll roads are generally not popular among drivers because they add a monetary cost to something that seemed free. However, the additional cost changes the calculus people make before choosing to drive. If the trip becomes too costly, a person may choose to travel earlier or later in the day, may choose to carpool to avoid the fee, or may choose an alternative mode.

In all of these cases, a vehicle is removed from the roadway at a time when there would be traffic congestion. Albeit a controversial project, we’re seeing this now along the I-66 corridor in Virginia.

3. Build more mixed-use, transit-oriented, and high-density development: People opposed to new development point out that adding even more people is the opposite of what they want. However, there is a distinction between being against traffic congestion and being against all new development.

Mixed-use, transit-oriented, and high density developments generate all the activity that increases residents' quality of life, while generating fewer vehicle trips. This solution doesn’t change the transportation between A and B, but rather brings A and B together, erasing the need for a transportation solution. Denser development also helps foster business because they require areas that draw lots of customers.

4. Prioritize people, not vehicles: Lastly, jurisdictions can change automobile-related requirements in their zoning ordinances and review practices so that all trips — not just automobile trips — are considered. For example, they can remove parking minimums for apartment buildings and prohibit drive-throughs, which encourage driving and penalize those who don’t. They can also lower the threshold where a developer would be required to build a road improvement.

This approach recognizes that assuming everyone drives is both problematic and detrimental to a neighborhood. By accommodating people before cars and reducing the number of road projects, driving doesn’t become the default option. That leads to fewer cars on the road. These options work best together: reducing reliance on automobiles by changing the built environment while simultaneously making transit, walking, and bicycling more convenient and affordable.

The only way to solve traffic is to reduce automobile use. If people are able to travel without relying on motor vehicles, fewer will be used — making cities better for everyone.