Resident Expert: Transportation and Environmental Sustainability

Samer Madanat, Dean of Engineering

Why electric cars and more public buses aren't enough to reduce global vehicle emissions

NYU Abu Dhabi Dean of Engineering Samer Madanat specializes in transportation infrastructure management. He's an expert in developing optimal transportation policies and solutions to improve the sustainability of transportation systems in cities, including highway and public transit networks. In other words, he develops efficient ways for people to get around with an eye on protecting the environment.

To reduce CO2 emissions from the transportation sector Madanat says the collective global society needs to be smarter about getting from point A to point B, whether by car or public transport. But how do we do that? Aren't we being ‘smart’ enough already by manufacturing hybrid vehicles and taking the bus more often? Madanat says it's more complex than that.

The consensus from experts is that there are three ways the transportation sector—and people as a key part of it—can make an impact on greenhouse gas emissions and mitigate climate change:

  1. Improved fuel and vehicle technology (electric and hybrid cars)
  2. Increasing urban density to reduce vehicle-kilometers of travel (increasing transit market)
  3. Improved operational management (better use of available capacity of road networks)

Many governments and companies are already committed to one or more of these concepts and are spending billions on products and transportation systems in the name of environmental sustainability. For example, both the public and private sector in nearly every city in the world have prioritized expansion of transit networks to reduce congestion. But is it working?

True or false? There would be no road-related emissions if everyone in the world drove electric vehicles.

False. Fuel technology and cleaner fuels play a role but cannot work on their own to reduce emissions. Electric vehicles, hybrids, and hydrogen fuel cell cars do achieve higher mileage efficiency but there is widespread consensus that a significant amount of CO2 emissions from the transportation sector is the result of building new roads and fixing old ones. Even pavements produce a significant amount of CO2. To overlay old pavements with an asphalt layer, you have to extract aggregate and produce bitumen from oil refineries. Then you need to transport it, mix it and lay it. So, if you fix roads or build new ones too often, emissions go up. But on the other hand, if the pavement is left to crumble, more fuel is consumed driving on rough roads, and again, emissions go up.

Highway traffic in Dubai.

The main reason that cities have so many traffic jams is not simply because there aren't enough lanes, but because we have not mitigated bottlenecks on our road systems. 

Samer Madanat, Dean of Engineering
True or false? Building more highway lanes will reduce congestion and therefore reduce emissions.

False. Although emissions rise when more people sit stuck in traffic with engines idling, adding lanes to a busy freeway is a short-term and expensive fix. Contrary to conventional wisdom, congestion is not simply the result of too much traffic and not enough lanes. It's like the law of supply and demand. If you reduce the price of a commodity, more people will demand it; create more road capacity and people will drive more. To reduce congestion, we need to improve road network efficiencies. The main reason that cities have so many traffic jams is not simply because there aren't enough lanes, but because we have not mitigated bottlenecks on our road systems. They can be less damaging if they are managed well. In some countries such as Japan, variable message signs direct drivers and force driving behavior upstream of the bottleneck. You can't cut in later, and that means disruptive lane-changing behavior is reduced.

Which one is more accurate?

A. If car companies manufactured more hydrogen fuel cell cars, there would be more hydrogen fueling stations.

B. If there were more hydrogen fueling stations, car companies would manufacture more hydrogen fuel cell vehicles.

It's a chicken and egg question. People won't buy hydrogen cars if there's no supportive infrastructure. But the private sector is saying, we're not going to build hydrogen refueling stations if no one is going to come. This is an area where the government should play a role and invest in the hydrogen fueling infrastructure.

Highway traffic in Abu Dhabi.
What works better: Asking for a transportation behavior change to protect the environment or forcing it?

As a government, you can either encourage people to take personal responsibility for their emissions or mandate behavior adjustments. Centralized governments have a huge advantage in this way. In the USA, transportation is the third largest source of CO2 so the trucking industry has been both mandated and incentivized to reduce emissions by purchasing more aerodynamic trucks (better fuel economy) and fitting new trucks with cleaner engines.

True or false? Old cities usually have better public transit systems than newer ones.

Not necessarily true. It's not about the age of a city but the density of a city. In some places in the world, cities were built before the arrival of the automobile. Those were the days when the only way to get around was a horse or a tramway. As a result, cities were quite dense and people had to live closer to each other and and close to where they worked. Density made public transportation a viable option in Europe, China and older cities in the Middle East like Cairo, Beirut or Damascus. After the arrival of the automobile, cities started to spread out. In the Western US, cities were developed for driving and can't be rebuilt today to become more dense. On the other hand, even though cities like Boston and New York have vast suburbs, the majority of citizens still live and work in population dense areas that are easily accessible by public transportation and, therefore, transit use is high. In China, cities like Xian are growing rapidly but density is preserved and public transportation is an attractive option.

True or false? Some cities are too spread out for public transportation to ever be efficient.

In my view, this is true. Having people drive less and reducing vehicle miles of travel makes sense for some growing cities. But for others, like Los Angeles and Houston for example, it's too late (I'm not very popular among some transportation authorities in California!). Los Angeles is so spread out that it's difficult to develop an efficient public transit system that people will use. For all their efforts and billions invested, the metro line in LA still carries less than 10 percent of its capacity. Efficient public transit requires people to live close to the transit lines or you must have very efficient feeder routes to the main lines. But even the feeder routes require dense neighborhoods for it to work and LA doesn't have that.

What is your assessment of transportation development in Abu Dhabi? How smart is it?

Abu Dhabi is making the same mistakes that cities like Amman made in the past three decades: imitating the automobile-centric transportation system of most US cities. The center of Abu Dhabi has relatively high density, which can support mass transit modes like Bus Rapid Transit (BRT). In BRT systems, such as those in Curitiba (Brazil) and Bogota (Colombia), modern buses have dedicated lanes and signal priority; such buses also have lower platforms for higher speed of boarding. BRT networks could cover much of Abu Dhabi, with branches expanding toward the airport, and could, if attractive enough for residents of the city, convince many to use them for their daily commutes.

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