Can public transport investment really fix traffic congestion?

Well, this is fine: traffic in the north west Chinese city of Xi'an on a smoggy day. Image: Getty.

Now and then, someone mentions that a particular transit project did not reduce traffic congestion, as though that were evidence of failure.

In fact, the relationship between transit and congestion is an indirect one. In most cases, it’s unwise to claim congestion reduction as a likely result of your proposed transit project. (In this post “congestion” means that volume/capacity ratio for motor vehicles on a roadway is high enough to substantially reduce average speeds.)

Road widening, however, is also not a very good way to relieve congestion, except in the short term. In his 1992 book Stuck in Traffic Anthony Downs described the effect of widening an expressway in terms of a “triple convergence”:

In response, three types of convergence occur on the improved expressway:

(1) many drivers who formerly used alternative routes during peak hours switch to the improved expressway (spatial convergence);

(2) many drivers who formerly travelled just before or after the peak hours start travelling during those hours (time convergence); and

(3) some commuters who used to take public transportation during peak hours now switch to driving, since it has become faster (modal convergence).

Downs is describing only the immediate effect of the road expansion. Further increases in traffic will come from any new development that is attracted to the road’s catchment as a direct consequence of its expansion.

Prof. David Levinson’s work in the Minneapolis / St. Paul region suggests that, while added capacity generates new vehicle trips, the effect is often not great enough to restore the previous level of congestion. However, your results will obviously vary based on the amount of development that occurs as a result of the new or expanded road. If this development adds enough new vehicle trips to fill the new capacity, traffic congestion can return to near previous levels.

So the only way to make the congestion benefit of new road capacity permanent is to severely restrict development in the catchment area of the road – an impossible bar in most cases. In fact, parties who will profit from further development in a corridor may be part of the political consensus in support of a road expansion, even as the same expansion is marketed to existing residents as a congestion reducing project.

Otherwise, there appear to be two broadly applicable ways to relieve congestion in a substantial and permanent way.

Economic collapse. Traffic congestion drops during economic slowdowns, because fewer people have jobs to commute to, or money to spend on discretionary travel. A complete economic collapse, which causes people to move away from a city in droves, is always a lasting fix for congestion problems.

Correct pricing of road space. Fundamentally, congestion is the result of underpricing. If you give away 500 free concert tickets to the first 500 people in line, you’ll get 500 people standing in line, some of them overnight. These people are paying time to save money.

Current, prevailing road pricing policy requires all motorists to act like these frugal concertgoers. Motorists are required to pay for road use in time, rather than in money, even though some would rather do the opposite – and our cities would be safer and more efficient if they could. Current road pricing policy requires motorists to save money, a renewable resource, by expending time, the least renewable resource of all.

So if transit isn’t a cause of reduced congestion, what is its role? Do transit advocates offer nothing in response to congestion problems that have many voters upset?

In fact, transit’s role is essential, but its effect is indirect.


1) Transit raises the level of economic activity and prosperity at a fixed level of congestion.

Congestion appears to reach equilibrium at a level that is maddeningly high but that can’t be called “total gridlock.” At that level, people just stop trying to travel. If your city is car-dependent, that limit becomes the cap on the economic activity – and thus the prosperity – of your city. To the extent that your city is dependent on transit, supported by walking and cycling, economic activity and prosperity can continue to grow while congestion remains constant.

To quite a comment left on my website, on an earlier version of this post: “Toronto achieved significant downtown employment growth without increasing road capacity after the 1960s, thanks first to increased subway ridership and later due to increased commuter rail ridership. Congestion is still bad on the roads and expressways into downtown, even with transit expansion, but the expansion of transit has permitted the downtown to grow beyond what the road network would have supported.” A similar pattern can be observed in many similar cities.

2) Transit enables people who can’t drive to participate in economic life.

Groups who don’t have the option to drive include many seniors and disabled persons, some youth, and a segment of the poor. Providing mobility to these groups is not merely a social service; it also expands participation in the economy.

For example, during the US welfare reform debate in 1994-96, government began raising pressure on welfare recipients to seek and accept any employment opportunity. For the very poor living in car-dependent cities, the lack of commuting options became a profound barrier to these job placements.

This is really an element of the previous point, since all employment, even of the poor, contributes to prosperity. But this has independent force for government because unemployed people consume more government services than employed people do. This benefit of transit should routinely be described in terms of economic efficiency, as I’ve done here, rather than appealing to pity or to alleged “economic rights,” as social-service language often implicitly does. The appeal of the social service argument is just too narrow, especially in the US.

Hey, at least the train is moving: just another rush hour in Manila. Image: Getty.

3) Transit-dependent cities are generally more sustainable than car-dependent cities.

They cover less land and tend to have fewer emissions both per capita and per distance travelled. The walking that they require is also better for public health, which produces further indirect economic benefits in reduced healthcare costs.

4) Intense transit service is essential for congestion pricing.

Congestion pricing appears to be the only effective and durable tool for ensuring free-flowing roads while maintaining or growing prosperity. Congestion pricing always causes mode shift toward public transit, so quality public transit, with surplus capacity, must be there for a pricing plan to be credible.


5) Surface exclusive transit lanes (for buses, rail, and arguably two-wheelers and taxis) improve the performance of emergency services.

This argument should be much more prominent, because even the most ardent car-lover will understand it. Few things are more distressing than to see an emergency vehicle stuck in traffic, sirens blaring. When confronted with this, all motorists do their best to help. But if the entire width of a street or highway is reserved for cars (moving or parked), and is therefore capable of being congested, it can be impossible to get out of the way of an emergency vehicle even if every motorist present has the best of intentions.

Emergency response should be one of the strongest and most obvious cases for surface transit lanes. Motorists understand the need to drop to a low speed in school zones, to protect the life of every single child. Why do we not accept come degree of delay to save a child who may be dying somewhere else, because the ambulance is stuck in traffic?

In the end, of course, “congestion” is not a good measure of the outcomes of transit. In fact, the very notion of congestion presumes a motorist’s view of the world. I agree with another commenter, Rodrigo Quijada, when he writes:

What we’d like to do in a city is to reduce TRAVEL TIMES. Reducing congestion is a way to do that, but in no way the only one. Over the decades, in places where car transportation has become dominant, people have got used to see travel times and congestion as the same thing, thus orienting their thinking and their solutions to reduce congestion. But this is essentially a confusion.

Still, in real-world transit politics, selling transit projects to current motorists is a necessity, and the current motorist is likely to see her problem as one of congestion. So it’s important to be clear on what transit can readily do for her.

  1. It can provide an alternative to driving which may be faster, more cost effective, and less stressful. This argument can be put quite selfishly: Good transit won’t eliminate congestion in your city, but it can eliminate it from your daily life.
     
  2. Transit helps reduce government spending on social services by enabling transit disadvantaged groups to participate in the economy. This obviously has a range of health and wellness benefit apart from its economic role.
     
  3. It can increase the level of prosperity at a fixed level of congestion.
  1. Its exclusive lanes protect emergency vehicles from congestion-related delays, potentially saving lives.

Jarrett Walker is an international consultant in public transit network design and policy, based in Portland, Oregon. He is also the author of “Human Transit: How clearer thinking about public transit can enrich our communities and our lives".

This article was originally written for his blog, and is reposted here with permission.

 
 
 
 

Mexico City’s new airport is an environmental disaster. But it could become a huge national park

Mexico City’s new Norman Foster-designed airport, seen here in a computer rendering, is visually striking but environmentally problematic. Image: Presidencia de la República Mexicana/creative commons.

Mexico City long ago outgrew the two-terminal Benito Juárez International Airport, which is notorious for delays, overcrowding and canceled flights. Construction is now underway on a striking new international airport east of this metropolis of 20m. When it opens in late 2020, the LEED-certified new airport – whose terminal building was designed by renowned British architect Norman Foster in collaboration with the well-known Mexican architect Fernando Romero – is expected to eventually serve 125m passengers. That’s more than Chicago O'Hare and Los Angeles’ LAX.

But after three years of construction and $1.3bn, costs are ballooning and corruption allegations have dogged both the funding and contracting process.

Environmentalists are also concerned. The new airport is located on a semi-dry lake bed that provides water for Mexico City and prevents flooding. It also hosts migrating flocks and is home to rare native species like the Mexican duck and Kentish plover.

According to the federal government’s environmental impact assessment, 12 threatened species and 1 endangered species live in the area.

The airport project is now so divisive that Andrés Manuel López Obrador, the populist winner of the country’s 2018 presidential campaign, has suggested scrapping it entirely.

An environmental disaster

Mexico’s new airport sits in a federal reserve. Image: Yavidaxiu/The Conversation.

I’m an expert in landscape architecture who studies the ecological adaption of urban environments. I think there’s a way to save Mexico’s new airport and make it better in the process: create a nature reserve around it.

Five hundred years ago, lakes covered roughly 20 percent of the Valle de Mexico, a 3,500-square-mile valley in the country’s south-central region. Slowly, over centuries, local residents – first the Aztecs, then the Spanish colonisers and then the Mexican government – built cities, irrigation systems and plumbing systems that sucked the region dry.

By the mid-20th century, the lakes had been almost entirely drained. In 1971, President Luís Echeverría decreed the area a federal reserve, citing the region’s critical ecological role for Mexico City. The smattering of small lakes and reforested land there now catch and store runoff rainwater and prevent dust storms.

The new airport will occupy 17 square miles of the 46-square-mile former Lake Texcoco. To ensure effective water management for Mexico City, the airport master plan proposes creating new permanent water bodies to offset the lakes lost to the airport and cleaning up and restoring nine rivers east of the airport. It also proposes planting some 250,000 trees.

The government’s environmental assessment determined that the impacts of the new airport, while significant, are acceptable because Lake Texcoco is already “an altered ecosystem that lost the majority of its original environmental importance due to desiccation and urban expansion.” Today, the report continues, “it is now only a desolate and abandoned area.”

Environmentalists loudly disagree.

Make Mexico’s airport great again

I see this environmental controversy as an opportunity to give Mexico City something way more transformative than a shiny new airport.

Nobody can entirely turn back the clock on Lake Texcoco. But the 27 square miles of lake bed not occupied by the airport could be regenerated, its original habitat partially revitalised and environmental functions recovered in a process known as restoration ecology.

I envision a huge natural park consisting of sports fields, forests, green glades and a diverse array of water bodies – both permanent and seasonal – punctuated by bike paths, walking trails and access roads.

The airport will come equipped with new ground transportation to Mexico City, making the park easily accessible to residents. Extensions from the surrounding neighborhood streets and highways could connect people in poor neighbourhoods abutting the airport – dense concrete jungles like Ecatepec, Ciudad Nezahualcoyotl and Chimalhuacan – to green space for the first time.

The nine rivers that empty into Lake Texcoco from the east could be turned into greenways to connect people from further out in Mexico State to what would become the area’s largest public park.

Space could also be reserved for cultural attractions such as museums, open and accessible to passengers in transit.


New master plan

This idea is not as crazy as it sounds.

As early as 1998, Mexican architects Alberto Kalach and the late Teodoro González de León proposed rehabilitating the lakes of the Valley of Mexico. Their book, “The City and its Lakes,” even envisaged a revenue-generating island airport as part of this environmentally revitalized Lake Texcoco.

Under President Felipe Calderon, Mexico’s National Water Commission also proposed building an ecological park in Lake Texcoco, which was to include an island museum and restore long-degraded nearby agricultural land. But the project never gained traction.

Granted, turning a large, half-constructed airport into a national park would require an ambitious new master plan and a budget reallocation.

But in my opinion, evolution and change should be part of ambitious public designs. And this one is already expected to cost an additional $7.7bn to complete anyway.

Toronto’s Downsview Park – a 291-acre former air force base turned green space – has transformed so much since its conception in 1995 that its declared mission is now to “constantly develop, change and mature to reflect the surrounding community with each generation.”

Local communities neighboring Mexico City’s new airport were not adequately consulted about their needs, environmental concerns and their current stakes in the Lake Texcoco area. A revamped park plan could be truly inclusive, designed to provide recreation and urban infrastructure – and maybe even permanent jobs – for these underserved populations.

Presidential race

Three of the four candidates in Mexico’s July 1 presidential election wanted to finish Mexico City’s new international airport. But eventual winner López Obrador was not so sure.

Early in his campaign, he said he would cancel it if elected. Instead, López Obrador suggested, a former air force base could become the new international terminal. It would be connected to Benito Juárez airport, 22 miles south, by train.

López Obrador has since said he would support completing construction of the new international airport if the remaining financing came from the private sector, not the Mexican government. Currently, some two-thirds of the project is funded by future airport taxes.

The ConversationLópez Obrador’s promise to review and likely upend the airport plan could open the door to its wholesale transformation, putting people and nature are at the core of a plan ostensibly designed for the public good.

Gabriel Diaz Montemayor, Assistant Professor of Landscape Architecture, University of Texas at Austin

This article was originally published on The Conversation. Read the original article.