Congestion and Pollution in Cities: Erroneous Measures?

The great weight that the car has as a means of mobility in large cities generates significant negative externalities in terms of congestion and pollution.

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The great weight that the car has as a means of mobility in large cities generates significant negative externalities in terms of congestion and pollution. The problem, which is extraordinarily serious in terms of lost time and public health, seems out of control and worsens year after year. Many cities in Europe have adopted low emission areas (such as Barcelona on 01/12/2017 and more recently Madrid with progressive entry into force as of 11/30/2018), while only a few have decided to establish congestion tolls. (London in 2003, Stockholm in 2006, Milan in 2008, Gothenburg in 2013 and Palermo in 2016). Added to this are the permanent claims for improvement of road infrastructures in congested cities. It is frustrating to see how the problem becomes entrenched and worsens in spite of the measures adopted, which transmits the idea of ​​endemic evil inherent in the big cities.

In this post we analyze the properties of the three measures we mentioned previously: investments in infrastructures, restrictions via quantities (low emission zones) and restrictions via prices (congestion tolls). This analysis will allow us to assess if there is a solution to the problem and, where appropriate, which measure is the most appropriate (more details in Fageda and Flores-Fillol, 2018). This entry complements and updates previous ones on this topic (here, here, here, here and here).

Road congestion in urban centers is explained because supply (infrastructure) is unable to absorb demand, especially in the early morning and late afternoon. The reason has to do with the coexistence of a fixed offer and a very variable demand (characterized by peak and valley hours). The congestion is translated into great traffic jams that cause problems to the occupants of the vehicles and to the inhabitants of the cities, who find their streets blocked by an excessive number of vehicles that produce noise and pollution. The relationship between congestion and pollution is clear, as the use of short gears at reduced speeds has a notable effect on the emission of polluting substances (Parry et al., 2007). These emissions cause the death of 3.3 million people a year in the world, 31,520 of them according to the European Environment Agency (info here), more than AIDS, malaria and flu together (Lelieveld et al. , 2015).


With data on cities around the world, TomTom produces a congestion indicator that measures the additional time a vehicle needs to access the city center with respect to a fluid traffic situation (info here). Thus, traffic jams in Barcelona and Madrid mean that a vehicle takes an average of 31% and 25% more time, respectively, compared to the decongested situation (2016 data). TomTom has also published a report on the cost of congestion in Spanish companies (info here). Noteworthy are the 119 extra hours at the wheel in Barcelona (equivalent to 14 working days) and 105 in Madrid. This time translates into a huge economic loss: 175.5 million euros in Barcelona and 187.5 million euros in the Spanish capital.

Atmospheric pollution

The World Health Organization (WHO) has a database on air quality in the most populated cities in the world that provides the concentration of suspended particles of type PM10 and PM2.5 (particles with an aerodynamic diameter less than or equal to at 10 and 2.5 microns, respectively). For some years now, the WHO has recommended the use of indicators based on PM2.5, since they are considered a better indicator of urban pollution due to their mainly anthropogenic origin. The effects of PM2.5 on our health are very serious due to its composition rich in very toxic components with a great capacity of penetration in the respiratory tract. According to the WHO Health Protection Guideline Values, an average annual concentration of 10 μg / m3 would be the lowest level from which an association between cardiopulmonary effects and mortality was detected; the risk increases with the concentration of particles as expected (WHO, 2005).

We explain the properties of the three main measures that can be adopted: investments in infrastructures, restrictions via quantities and restrictions via prices.

Investments in infrastructures

In urban centers with mature infrastructures, investments aimed at improving supply have a low social return since their costs are very high, they can have regressive effects (insofar as they are financed with broad-based taxes from which they mainly benefit drivers) and are generally ineffective. The latter is due to the fact that the improvement in supply can be matched by an increase in demand in response to the reduction in the generalized cost of travel (Duranton and Turner, 2011).

Restrictions via quantities

The most used in Europe are the low emission areas (applied in Barcelona and recently in Madrid). These measures are:

  • Inefficient. They are indiscriminate and expel drivers with great need to access the city center.
  • Ineffective in the medium term. They progressively lose their effectiveness in preventing traffic jams as the fleet of cars is renewed (although they can be effective in reducing pollution).
  • Regressive. They affect the most polluting vehicles, which are the oldest and belong to families with lower purchasing power.

Restrictions via prices: congestion tolls.

These measures have the virtue of being:

  • Efficient. Those users who value the infrastructure more are precisely those who end up using it.
  • Effective. They can substantially reduce traffic from the moment of its implementation.
  • Not regressive. if they are well designed. On this issue it should be noted that: i) their amount is usually low, ii) they involve a certain saving in fuel by reducing traffic jams, and iii) they generate resources that can be used to improve public transport or progressive social policies.

In addition, a recent study (Bernardo et al., 2018) with European data shows that low emission zones are not effective in reducing congestion, while congestion tolls do work (confirming previous partial studies: Eliasson, 2008, Santos and Fraser, 2005, Andersson and Nässén, 2016, Gibson and Carnovale, 2015, among others).

Therefore, we find that in many European cities erroneous policies are being applied that are inefficient, inefficient and regressive. We maintain that the problem has a solution if the appropriate policy is applied. We propose the establishment of a congestion toll that regulates access to the center of Madrid and Barcelona during peak hours. This system can permanently and permanently solve the problem of traffic jams, while at the same time helping to substantially mitigate the problem of air pollution. In addition, it is simple to design and implement and produces immediate results while generating additional resources.

The unpopularity derived from paying a new toll is obvious. However, the experience of the cities where it has been applied limits this obstacle in the short term. In Stockholm, social support for the toll went from 30% to 70% one year after its application (Eliasson, 2008), once citizens directly experienced its effectiveness (traffic was reduced by 20% immediately).