I've noticed that in and around London pedestrians, joggers and cyclists don't always respect the minimum 2 metres' distance of social distancing recommended to limit the spread of Coronavirus.
The Guardian, helpfully, points out another anti-social behaviour in the streets which is more dangerous now: spitting.
But new research has uncovered that the 2 metres' distance deemed sufficient for people standing still, for example when queueing outside a shop, is not enough in times of COVID-19 when someone is exercising.
These are the conclusion of a Belgian-Dutch study.
There is some confusion among the public on this question, in view of the widespread notion, supported by the WHO (World Health Organisation), that the new virus is not spread via the air but by contact with people or surfaces. This is because the aerosols - minuscule particles floating in the air - containing the virus don't remain in the atmosphere long enough to cause a risk.
However, in a situation in which a person is walking, running or cycling after another, the droplets may still be in the air before they settle down on a surface.
Civil Engineering and Sports Aerodynamics researchers at Belgium's University of Leuven and the Netherlands' University of Eindhoven created simulations to investigate these risks.
Professor Bert Blocken, Study Coordinator of the white paper just published, in an interview to The Brussels Times explained why the measures for people standing still are "ineffective" for those walking, running or cycling:
When people speak, exhale, cough or sneeze they generate droplets, and while the largest droplets tend to fall to the ground first, the smaller ones can remain in the air a bit longer, so it is important that a person who is behind another does not walk into this cloud of droplets.The Urban Physics, Wind Engineering, Sports Aerodynamics expert has extensively studied the aerodynamic advantages of slipstreaming in cycling, which is the act of a cyclist riding behind a team-mate or rival to save energy and thus gain a benefit: in sport terminology this is usually called "drafting".
But in the Coronavirus pandemic the disadvantages and dangers of this behaviour are remarkable.
The simulations show that the respiratory droplets of someone potentially infected with the virus could come into contact with anyone located behind him by travelling through a slipstream or wake, the area that a person in movement creates behind him.
From Blocken's simulations it appears that social distancing requirement may be smaller for two people running or walking beside each other, as the droplets land behind them. When they are positioned diagonally behind each other the risk to catch the droplets of the lead runner is also smaller. The risk of contamination is the biggest when people are just behind each other, in each other’s slipstream.
The researcher compared slipstreams to a vacuum or drag effect which occurs when the regular airflow is disturbed by someone who is in motion.
Luckily, although slipstreams can even be as long as 10-15 metres, Blocken observed that they remained quite narrow and that respiratory droplets tended to evaporate quite quickly.
Based on this study's results, the scientist advises greater social distances for people on the move:
- those who walk in the same direction in one line should maintain a distance of at least 4–5 metres
- for running and slow cycling the distance should be 10 metres
- for hard, fast cycling it should be at least 20 metres
- for overtaking, cyclists should be in a different lane at a considerable distance, e.g. 20 metres.
PHOTO CREDIT
Image by Maciej Cieslak from Pixabay
