Experience shows Delhi’s “even/odd” car plan won’t cut massive pollution – U.S. expert
In response to a reprimand from the Delhi High Court, the Indian capital has announced that it will trial a policy starting Jan. 1 that will bar cars from driving on alternating days. The intention is to cut vehicle emissions – arguably one of the largest causes of air pollution in the city – by half.
Mexico City introduced a similar programme in 1989 called Hoy No Circula (You Don’t Drive Today). While that city’s air quality is now much improved, experts have cast serious doubt onto whether the programme led to this success. Dr. Lucas Davis, Associate Professor at the Haas School of Business at the University of California-Berkeley and Faculty Director at the Energy Institute at Haas, authored a 2008 research paper in which he concluded that Hoy No Circula had resulted in no decrease in driving or pollution in Mexico City. The research had no corporate sponsors.
Below are excerpts from an interview with Davis:
Q: You wrote a paper about Mexico’s Hoy No Circula programme. Can you start by saying how effective that’s been?
A: First, let me just say that Mexico City’s programme works by restricting driving based on the last digit of the vehicle’s license plate. So for example, if your vehicle’s license plate ends in a five or a six, you can’t drive on Mondays.
Using hourly data from pollution monitors, I looked to see what the effect of the programme was, when it was first implemented, on air quality. And I find no evidence that the programme improved air quality. I looked at six different measures of pollutants, I looked at a bunch of different hours of the day, and I crossed pollutants and the hours of the day, and I find no evidence that the programme improved air quality.
Q: Did the programme lead to any positive outcomes?
A: It was hoped that the programme would encourage people to substitute to public transportation. I looked at data from the Mexico City subway and bus system and found no evidence of an increase in ridership. This is pretty disappointing, because public transportation is much lower emitting than vehicles.
So this is pretty disappointing, but maybe not surprising. We’ve found around the world, that drivers have a revealed preference for fast and convenient transportation, and it can be very difficult to get drivers to switch to public transportation.
Q: I know you wrote about this in your report, but what, in general, did you see people doing on the days when they couldn’t drive their cars?
A: What I found is that sales of new vehicles increased, and the number of registered vehicles increased. So what it looks like is that many households responded to the programme by acquiring an additional vehicle.
This is actually quite a disappointing, perverse outcome, because it means – well, first, it makes sense: You can’t drive your primary vehicles on Mondays, but now having a secondary vehicle – even an older vehicle – is helpful, because you can use it on Mondays. But often, households have more than one driver per household, and so this means that the programme could cause total driving to increase, potentially substantially. That secondary vehicle ends up being used on more than on just that day when the primary vehicle is restricted.
Q: There have been some similar programmes conducted in other cities, notably in Beijing in the leadup to the Olympics. Do you know or feel comfortable commenting on whether any of these other cities have seen any success?
A: I’ve seen no evidence that this type of license plate-based restriction has been successful anywhere. Beijing did manage to improve air quality during the 2008 Olympics, but it’s difficult to learn much from that, because at the same time Beijing was implementing driving restrictions, they also closed down a number of power plants and other industrial facilities and took a number of other draconian measures that, all together, did manage to improve air quality, but it’s very difficult to know what effect the driving restrictions themselves had.
Q: Delhi has a couple unique traits that I wanted to get your opinion on. On the one hand, it has an unusually high number of taxis – if you include autorickshaws it’s one for every 60 residents – but on the other hand, more than half of taxis are autorickshaws, which run on natural gas. Do you think that either of these, or any other traits about Delhi, might lead to a different outcome compared to Mexico City?
A: Yeah, I think that the success of driving restrictions depends on what available substitutes there are. The availability of these lower-emitting, natural gas rickshaws actually is some cause for optimism. Rickshaws are a form of private transportation that’s fast, convenient, and available, and if the programme could succeed in leading people to substitute widely to natural gas rickshaws, you could see a decrease in emissions.
Nevertheless, I’m very discouraged to see this type of indirect policy rolling out around the world. Economists have argued for about a century that the way you address externalities is through pricing mechanisms. What I’d like to see is more direct policies aimed at driving. That means increasing gasoline and diesel prices as well as congestion pricing where available.
Q: Moving on then, what can you tell me about the costs to citizens and to the city of implementing a programme like this?
A: Driving restrictions are appealing to city governments in part because they don’t require large city expenditures. These programmes are typically enforced by city police, so there is no immediate investment required for enforcement, and this kind of policy can be implemented very quickly, as you’ve seen around the world.
The cost instead are really borne by drivers. This kind of policy is extremely inconvenient for drivers. As an anecdote, in Mexico City, truckers line up outside the city and wait until 10 pm when the programme restrictions end. And so you just have this line of truckers waiting outside the city, waiting for the restrictions to end. So these are costly policies for commercial vehicle owners and for households, who have to come up with alternative modes of transportation on these days when they can’t drive.
Q: Mexico City has over time has found some success in getting its air pollution problem under control. If Hoy No Circula wasn’t responsible, what policies should get the credit?
A: Mexico City’s air quality has improved over the last two decades primarily because of new vehicle emission standards and improvements in the environmental characteristics of the gasoline that is sold in Mexico.
Mexico made the decision about two decades ago to adopt U.S. emissions standards for new vehicles. So this has been enormously successful and meant that over time the vehicle fleet has gotten much cleaner in terms of emissions characteristics.
Q: So finally, a lot of people in New Delhi’s primary concern isn’t the NO2 or the Ozone, that as far as I understand was the big concern in Mexico City, but instead it’s particulate matter, for which it seems that transportation plays a role, but there are several other factors. Do you think that’s a significant difference for a programme like this?
A: Scientists are very clear now that particulates are the most pollutant for human health, so addressing particulates is an enormous priority. Unfortunately, it’s not at all clear that driving restrictions are a way to do this. As you suggest, vehicles are just one of many sources of particulates, so it’s not clear at all that going after vehicles is the best method for addressing particulates.
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