Traffic Pollution Modelling — Article Summary

After several posts about pollution sources and effects of street pollution, I thought that it would be interesting to look at how researchers observe and track pollution. One way that they do so is by modelling; modelling is a useful tool to have for long term predictions, but as this paper by Berkowicz et al (2006)  will show, there is still room for improvement for these models.

The paper summaries comparisons between data obtained from traffic pollution modelling with the COPERT model and OSPM mdoel (Operational Street Pollution Model) and that of actual street level measurements. They found that there are significant underestimations present in the modeled data, and proposed a new set of parameters (traffic emission factors, to be precise) which appears to give more accurate results.

Why is modelling prone to inaccurate data? This is because of what modelling actually is. For instance, modelling looks at data on source emissions, which is often calculated based on 1) traffic data and 2) vehicle specific emission factors. These are sometimes not actual measurements; for instance, the authors note that vehicle specific emission factors are often estimated with different methods and are found not to just vary according to vehicle type, but also on driving conditions — this is something that had not been taken into account.

Parameters assigned to different models may also be problematic. For instance, the COPERT modelling in European context aims to be a simple method for estimation of national emissions of traffic related pollutants. It uses vehicle emission factor, which is a function of vehicle speed; differentiation between vehicle types, fuel used, engine capacity or weight, emission legislation category. It also includes correction for cold starts and degradation of emission reduction equipment with mileage. This sounds good, and simplified, but unfortunately the authors note that the parameters used may be erroneous.

For example, they thought that emissions predictions on the national is not quite possible because it is difficult to isolate source pollutions on the national level — there are many variables that complicates pollution levels, as compared to merely street measurements.

Meanwhile, the Danish OPSM model (Berkowicz, 2000; cited in Berkowicz et al, 2006), is a simple parametrized model (parametrization of flow and dispersion conditions — how air pollutants are dispersed in the atmosphere —  in street canyons). The good thing about this model is that it requires little CPU time so that the model can be modeled for longer time periods — this is useful because this is precisely what models try to do (predicting what will happen in the long term given a certain set of conditions)

However, an important result from this paper is that while models provide a good estimation for street level pollution, they are rather unreliable when it comes to providing data urban /regional studies. This is because it is easier to isolate pollution sources on the streets, as compared to that of the whole region. Despite so, traffic pollution modelling is a tricky process.  Factors involved in modeling may be inaccurate, and may result in underestimation of data (for instance, too low emissions attributed to heavy diesel traffic (5% of traffic) resulted in  underestimations of NOx on the street of Jagtvej, Copenhagen, by almost 30%, and an underestimation of CO2 by 60%.

The authors concluded the paper by warning readers that it is essential to note any potential biases from inaccurate emission values attributed to different vehicles, and calls for more comparison between models and actual street level measurements. These information will better improve existing models.


Berkowicz, R., Winther, M. and Ketzel, M. (2006). Traffic pollution modelling and emission data. Environmental Modelling and Software 21: 454-460

Throwaway Culture a cause of Increasing Pollution?

Clean Water Action (CWA), an American environmental advocacy group working for clean, safe and affordable water in the USA, found from their research in Oakland, Richmond, San Jose, and South San Francisco from October 2010 to April 2011 that the biggest source of rubbish on the streets is fast food, accounting for 49% of the total rubbish collected. They also claim that up to 21% could have been eliminated by reusable alternatives.

The contribution of rubbish thrown on the streets to pollution is something authorities should look into and try to minimise. Not only is rubbish unsightly on the streets, it also contributes to the pollution of waterways (For example, stormwater pollution, which I briefly wrote about 2 months ago!). In addition, improper waste management is not enviornmentally sustainable — an article from The Guardian by Walshe (2013) describes how New York’s waste management used to include using garbage trucks that are sent to landfills, and how residents are affected by not just the sight but also the stench of rubbish.

What other cities have been doing include recycling and conservation efforts to reduce the amount of rubbish generated, so it is not merely a shifting of rubbish out of sight but includes actual management. However, Walshe (2013) points out that not only is it hard to change the disposable mentality of New Yorkers, the lack of public recycling facilities and ineffective measures (such as the nickel deposit on bottles) are factors affecting for the lackluster recycling measures in the city of New York. For instance, Walshe notes that the “nickel deposit on bottles” are not seen as valuable enough to encourage people to claim them by recycling — most people do not feel that the nickel (approximately 5 cents) is worth the trouble.

This is something that perhaps we can consider when thinking about measures to target pollution: can we think of something that people will be willing to comply with, and yet economically sustainable? I do not think that a ‘carrot and stick’ approach will necessarily work in the long run (perhaps the ease of improper disposal of rubbish and excessive use of energy resources, for example, is an easier option for many people such that small monetary benefits may not be significant), and the change in mindset is something that is much harder the cultivate but yet much more sustainable.

How then, do we change behaviour? In these articles’ cases, how do we modify the throwaway culture?

As cliche as it sounds, we have to work from the ground. And before we can start thinking about changing the mindsets of other people, we should perhaps look at how we can modify our daily habits to reduce the amount of disposable trash that we generate. For instance, we could bring our own containers when ordering take-aways (it will be interesting to know how successful is ProjectBox by NUS SAVE — the initiative lets staff and students obtain a $2 discount off their next canteen meal if they use their own containers for 10 times). I have not tried this myself, but the last time I am at the canteen, I still saw these printouts pasted on the canteen stores.


Cheeseman, G. (2011) Fast Food Garbage Makes up 50% of street (and Pacific Gyre) litter. Triple Pundit. [Online]. Retrieved from: [last accessed: 27 March 2015].

Walshe, S. (2013). New York’s Waste Management plans don’t address throwaway culture. The Guardian [Online]. Retrieved from: [last accessed: 27 March 2015]

Gadgets to monitor air quality at Edmonton

I came across this interesting initiative to help raise awareness on air pollution in the city of Edmonton, Alberta.

In response to the poor air quality (in particular, during the 2009/10 and 2010/11 winters when calm wins and a temperature inversion trapped air pollutants in the city) in Edmonton, Alberta Capital Airshed (a provincial industry and environmental advisory group) are partnering with city authorities to make portable and personal air quality monitors for citizens in the city by making use of crowd-mapping software with the help of HabitatMap. This is done with the aim of raising awareness about the dangers of poor air quality which residents may not be aware of, such as that of PM2.5 which are too small to be seen with the naked eye.

How the monitors work is that participants will bring their monitors along, and the monitors will take in data which will be uploaded real-time to an online map that is available to the public. These monitors measures the amount of PM2.5 in the air by running a small stream of air past an infrared LED light. A small sensor located in the device measures how much light is scattered by the PM2.5 particles in order to detect the PM2.5 concentrations in the air.

Here is a picture of the monitor!

Picture of the air quality monitor which will be provided to some residents of the city of Edmonton. Source:


Slote, E. (2015) New air quality gadgets demystify pollution. Edmonton Journal [Online] Retrieved from: [Last accessed: 21 March 2015]

Noisy Roads

Noise is a prominent feature in many urban areas, coming from not just transport but also industries. There are various studies done on the effect occupational and environmental noise exposure on humans, such as that by Stansfield & Matheson (2003), and also the effects of noise exposure on the ecology system (Forman & Alexander, 1998). I’ll try to give a brief summary on these two papers.

Noise as an environmental stressor and nuisance (Stansfield & Matheson, 2003), and is found to cause progressive loss of hearing (under continuous exposure), with an increase in the threshold of hearing sensitivity. Other than auditory effects on health, continuous exposure to noise can give rise to a host of other problems for the human population too.

  • Sleep disturbances
  • Impaired cognitive performances
  • Cardiovascular Diseases
  • Psychological disorders

Meanwhile, Forman & Alexander (1998) highlights how roads impact local ecology with various local hydrological and erosional effects. I will however, focus on the section on ‘Vehicle Disturbance and Road Avoidance‘. The research highlights how different species are affected by vehicle disturbances, and in particular, songbirds who are extremely sensitive to noise levels (for instance, the most sensitive woodland species, the cuckoo, showed a decline of density at 35 decibels.) The article further describes the effect of traffic noise in affecting animals, which not only includes increase in stress levels due to the noise, but other disturbances and changes to the ecosystem which includes the barrier effect of roads which affects the population of various species and their distribution (one example is the genetic structure of small local populations of the common frog in Germany).

Reading this article reminded me of a series of pictures I saw online about wildlife bridges.

I think I’ll need to read more about the benefits of such bridges, but I can see how these bridges can have the potential to remove the barrier effects of roads, and reducing the number of road kills if animals use them. I doubt they will remove the effects of toxic particulates and noise from vehicles though, but this is the least we can do along existing highways that have already been built to minimize further damage to local ecology.


Forman, R. and Alexander, L. (1998). Roads and their major Ecological Effects. The Annual Review of Ecology, Evolution, and Systematics 29:207-231

Stansfeld, S. and Matheson, M. (2003). Noise pollution: non-auditory effects on health. British Medical Bulletin 68: 243-257

The World Geography (2012) Unusual Bridges for Animals — Wildlife Overpasses. [Online] Retrieved from: [Last accessed: 15 March 2015]

Light Pollution on streets

I searched “Night” + “Singapore” on Google images, and what came out were photos that look like this — dazzling with lights. I guess these image are almost like a symbol of modernity and progress,  a 24-hour global city. For instance, in recent years we see the Singapore Tourism Board promoting events such as F1 Night Race in Singapore. I hope that this will be a starting point for this blog post.

Few of my previous blog posts have mostly touched on air pollution, and I thought I would focus on something different this time round.

In this ABC Online article, “darkness” was described as an “endangered resource” — we are cutting ourselves away from the night sky, which is a “source of inspiration, meditation and reflection”. Not only are we disrupting ecosystems and wildlife, scientists have found that artificial light at night contributes to sleep disorders, which are in turn tied to many different diseases.

Light pollution, it seems, includes not just monetary costs (inefficient energy usage) but also environmental and health costs.

Some solutions proposed includes smart lighting technology (by Amsterdam-based company Tvilight), which aims to create lighting systems that responds to the amount of traffic and pedestrians in the area so as to reduce light pollution. In order words, providing what that is needed without wasting excess and necessary lights.

Is this something that we should consider? Or are we too fearful of the dark (after all, darkness is often associated with danger too) or that we will lose the vibrancy of the city?

To end off, here is a video of Earth from the International Space Station (just for fun! and for us to get a sense of how much light are we emitting from Earth).


Funnel, A. (2015). The Dark Side of Light. ABC Online. [Online]. Retrieved from: [Last accessed: 11 March 2015]

Under the Dome [Documentary]

Recently (28th Feb 2015), former Chinese journalist Chai Jing released an anti-pollution documentary, “Under the Dome”, which talks about China’s horrendous air pollution and is critical of the Chinese government’s policies which she blames for the country’s pollution crisis. She brings the audience through the issue with charts and diagrams through a presentation in a manner similar to Al Gore’s “An Inconvenient Truth”.

With the documentary going viral over just a few days, the Chinese government has imposed a ban and links to the documentary were pulled off from Chinese major video sites. The government has yet to comment on this to date.

Even though this documentary is not solely about street pollution (and is more about pollution specifically in China), I thought that this will be something interesting and definitely relevant to what we are studying in school right now. For a start, here are some issues that we should consider:

  • Why did China impose a ban on this documentary? Does that mean that what the documentary says is false or that the government is refusing to acknowledge the truth? Do they have something to hide?
  • Pollution is not simply about the physical effects of the pollutants on the environment; it is implicate in political decisions and has profound effects on both the social and economic spheres. This should prompt us to consider various factors contributing to pollution problems when assessing them.
  • Beyond the environmental effects of pollution, the internet is an interesting medium too — is it a whistle-blower? Can it prompt governments to take action? Raise awareness amongst the internet population? How can activists make use of the internet medium to bring their messages across to the wider public?
  • Of course, we should not forget that every documentary has its own biases. As such, we should not be taking in facts from documentaries (not just this one) mindlessly and should verify them before taking them as “justified beliefs”. We should also be cognisant that statistics (charts, data) can be manipulated to serve a particular purpose.

Meanwhile, here’s the Youtube link to the documentary. It is rather long (about 1hr 40mins) but it is worth the watch. I have included the version with English subtitles! Do have a look!


Chen, T. (2015). Pollution Documentary Pulled from Chinese websites. Wall Street Journal — China News. [Online] Retrieved from: [Last accessed: 7 March 2015]

Pittsburgh’s Air Pollution (1940s vs Today)

I saw this BuzzFeed article contrasting the difference in air pollution (through photographs) in Pittsburgh’s streets almost 70 years ago. (Do take a look!) The contrast is quite startling; seeing photographs of the hazy air (the outlines of buildings nearby are obscured) gives a better picture of just how severe pollution issues are in the past too.

While looking through the pictures, I felt quite happy that there is much progress for the better, and this made me wonder if it is possible for many highly polluted streets and regions to improve their air quality too. What is important to note is that measures take time — perhaps, we cannot expect air quality to improve overnight. But we can be hopeful that many decades later, there is a possibility of cleaner air.

Indeed, the Atlantic had used these pictures to tell netizens who are criticising Beijing’s air quality that it takes time, and Pittsburgh took close to a century to reduce the amount of smoke and soot particles in the air to the level it is at today. Contrast Pittsburgh’s development in the 19th century as the city, powered by coal, emerged as one of the main metalworks industries in the country with Beijing’s excessive coal powered power plants today.

This is Pittsburgh back in the 1940s. Source: [Last accessed: 1 March 2015]

After looking at these pictures, I have some thoughts (these are not necessarily referring to Pittsburgh and Beijing; I am thinking about many cities around the world in general):

1. The political will of the city/country’s authorities

After looking through the pictures, it might be tempting to say that severe air pollution around the world is acceptable for developing cities, and that they just need to be given a longer time to solve their air pollution issues because they are inevitable with industrial development. I think that it is unacceptable to say that just because other countries were able to pollute the air without much dire consequences (laws were not as strict as those today), one should be permitted to pollute the air as much as they would want to. It may be unfair for countries who are at the other end of the developmental ladder, but I feel that there is a responsibility towards not just a country’s own citizens, but citizens of the world once there is ample evidence and knowledge on tackling these issues.

That said, we should be aware of the unequal power relations on the world stage — would developed countries push the developmental ladder away from developing countries? Ideally, developed countries with the expertise and experience should provide their technological known-how for other countries to tackle the same problem they faced many years ago, but which country is entirely selfless to do that without any reservations or motives (settling a deal, etc)? I think not.

2. The situation may not have improved as much as we thought it had

For instance, back to Pittsburgh: it is reported in 2014 that the air quality is still bad despite improvements, due to shifts towards natural gas from coal-powered plants, with increases in unhealthy ground-level ozone. Soot and smoke particles may have declined, but many cities around the world are facing a new set of pollution problems which are less visible. PM2.5, carbon dioxide and nitrogen dioxide are just a few examples.


Hopey, D. (2014). Pittsburgh region still gets poor marks for air pollution. Pittsburgh Post-Gazette. [Online] Retrieved from: [Last accessed: 1 March 2015]

Madrigal, A. (2013). Aghast over Beijing’s Air Pollution? This was Pittsburgh not that long ago. The Atlantic. [Online] Retrieved from: [Last accessed: 1 March 2015]