CBC Science reporter Emily Chung writes for CBC’s excellent “What On Earth?”  podcast and weekly newsletter that  explores environmental issues.

Last week I spoke to Dr. Chung and we pondered an interesting question~why are we not connecting the fact that slower speeds on highways and cities are also a way to cut back on greenhouse gas emissions and air pollution?

As Dr. Chung writes “According to Natural Resources Canada, driving a vehicle with an internal combustion engine at 120 km/h burns 20 per cent more fuel than driving at 100 km/h. An Ontario law that requires trucks to install technology to limit their speed to 105 km/h was estimated to have reduced greenhouse gas emissions by 4.6 megatonnes between 2009 and 2020. That’s largely because air resistance increases exponentially at higher speeds, reducing a vehicle’s fuel efficiency and generating more pollution per kilometre.”

I have already written about  The Netherlands where under European law nitrogen oxide emissions must be mitigated before roads, housing and airports are built. In order to build 75,000 new dwelling units this year, the Dutch government lowered daytime highway speeds. In the Netherlands 50 kilograms of nitrogen compounds per hectare  are released into the environment annually  where the average in the rest of the  European Union (EU)  is 15 kilograms per hectare.

The  EU is restricting levels of air pollutants based upon World health Organization targets, and in the Netherlands 11 percent of nitrogen compounds come from vehicular traffic. It made sense to reduce that to meet pollution targets.

It is NOT the chemical element of nitrogen that is the issue but the chemical compounds created when oxygen or hydrogen is added. As DW.com reportsAmmonia contaminates groundwater and nitrogen oxides contribute to respiratory diseases and, according to the European Environment Agency, were responsible for 68,000 premature deaths across the EU in 2016.”  

 I wrote about the new handbook put out by NACTO (the National Association of City Transportation Officials) that recommends the adoption of slower speeds in cities to make them less deadly  and more livable. While the handbook has great data, it does not include any correlation between speed and increased emissions. The handbook does point out that 2018 data from the National Highway Traffic Safety Administration found that speed factored into 25 percent of all fatal crashes that year.

It is people like Professor Marianne Hatzopoulou, Canada research chair in Transportation and Air Quality at the University of Toronto who is leading the way in making the connection for North Americans. Dr. Hatzopoulou points out that it is  not only speed that factors into nitrogen oxide  emissions but speed changes in accelerating and braking.

Dr. Fred Wegman,  an emeritus professor of traffic safety at Delft University of Technology is  credited as a  developer of the “safe systems” approach to road management and recognized as such at the 2019 International Road Safety Symposium in Vancouver.

By adopting principles aimed at recognizing the safety of all road users, The Netherlands experienced a 49 percent reduction in road fatalities.

Dr. Wegman is  the person saying that  while reducing road speed saves lives, politically elected officials will find reducing road speed for basic sustainability reasons would be a more palatable rationale. Tying slower vehicular driver speeds with mitigating climate change accomplishes the same goal, that of safer roads, less traffic deaths, and fewer serious injuries.

It is time for this discussion to start in North America.



Images: mprnews, nationalauditoffice



  1. In the Netherlands in a collision between a car and a cyclist or pedestrian the motorist is deemed automatically at fault. That goes a long way to reducing collisions.


    Based on this post one could be forgiven for thinking the Dutch are laggards in controlling their pollutants compared to the rest of the EU. The figure of 50 kg hectare compared to the EU average of 15 sure makes them look bad, doesn’t it? Only the population density in the Netherlands is 416 per sq. km whereas the EU average is 111. If you exclude the massive 20% of the Netherlands that is water the figure is 520 per sq.km. But even using the lower figure the Netherlands produces less nitrogen compounds per capita than the EU average.

  2. Well if we’re talking sustainability and roads, let’s talk about the long line of idling cars I encountered on Denman Street yesterday. The reason: the much-hyped Beach Ave. Bikeway forces all cars heading SW on Denman to turn up Davie, therefore vehicles were stuck trying to make left turns 3-4 per light cycle, in the face of a steady stream of oncoming traffic.

    1. I love it when motorists spewing their filth blame cyclists for their pollution.

      1. Are you interested in reducing GHG emissions -removed as per editorial policy=
        Editor’s Comment~BE KIND.

        1. Are you interested in reducing GHG emission or are you merely interested in blaming others for your emissions?

        2. providing more space for cars increases the number of people who will drive and increases pollution from driving. Reducing the space available for cars does the opposite. So, yes, if you want a yes or no, then the answer is yes.

          1. Increasing road space only induces more cars when population also increases. Want to slow the use of cars, then slow the population growth. You naively seem to think the cars just disappear in the face of things like Beach Avenue, they don’t. Like water, the flow goes elesewhere, likely slower and creating more emissions.

            If you really wanted to drop emissions you’d petition for the government to replace every motorized vehicle with an electric one. There seems to be plenty of money to go around lately. Let’s make that bold step for the climate!

          2. Motor vehicle volumes have been in decline in Vancouver – and especially downtown – for decades, even as the population and jobs have grown substantially. That’s a bolder step for the climate than EVs can possibly be.

            This is also not a Vancouver phenomenon although it’s still fairly rare in North America. That decline in Vehicle Kilometres Traveled is happening throughout advanced economies as the world globalizes and private cars become an increasing liability.

    2. I guess you have never been on Denman before by that comment. Denman is in general traffic jammed on weekends and in the early morning / afternoon. Why? Because to this day the city still allows on street parking and many people try to cut through there instead of going down the main arterial routes (e.g. Georgia).

      But yes, it’s the bikes that cause all these cars to block each other.

  3. Georgia is also jammed at times- —–C O V discourages using alberni——— Yaletown & cambie bridge bound traffic should have direct alberni access from stanley park courseway

    1. Or fewer people should drive. That would have so many benefits including reduced GHGs.

      Alberni comes to grinding halt at Burrard anyway. It wouldn’t solve the problem. Not that more roads ever does.

    2. Editor’s Note: Deleted as per editorial policy. Off Topic. Please review our policy.

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