I’m not yet sure how related this is to Wei_Dai’s answer, but found a medium article exploring “how far away to be from others who are walking in front of you”. It references a couple other non-english articles, and one english… translation (I think?) on urbanphysics.
Some researchers ran computer modeling of what happens to saliva
The researchers came to this conclusion by simulating the occurrence of saliva particles of persons during movement (walking and running) and this from different positions (next to each other, diagonally behind each other and directly behind each other). Normally this type of modelling is used to improve the performance level of athletes as staying in each other air-stream is very effective. But when looking at COVID-19 the recommendation is to stay out of the slipstream according to the research.
The results of the test are made visible in a number of animations and visuals. The cloud of droplets left behind by a person is clearly visible. “People who sneeze or cough spread droplets with a bigger force, but also people who just breathe will leave particles behind”. The red dots on the image represent the biggest particles. These create the highest chance of contamination but also fall down faster. “But when running through that cloud they still can land on your clothing” according to Professor Bert Blocken.
Out of the simulations, it appears that social distancing plays less of a role for 2 people in a low wind environment when running/walking next to each other. The droplets land behind the duo. When you are positioned diagonally behind each other the risk is also smaller to catch the droplets of the lead runner. The risk of contamination is the biggest when people are just behind each other, in each other’s slipstream.
On the basis of these results the scientist advises that for walking the distance of people moving in the same direction in 1 line should be at least 4–5 meter, for running and slow biking it should be 10 meters and for hard biking at least 20 meters. Also, when passing someone it is advised to already be in different lane at a considerable distance e.g. 20 meters for biking.
This suggests to me that we don’t just want to consider distance. Time and speed are both elements here too. I think that is actually something people can understand intuitively if they get some basic information. Most people are not challenged with knowing where they need to be to catch the fly ball. Here they just need to have a reasonable sense of where not to be.
So the message really isn’t X distance but several factors that can include a distance metric.
However, the other aspect here is not safe (pick you metric) versus not safe. It’s about level or risk and what that implies about actions to take. This could be anything from what types of PPE one uses to thinks like everyone adopting inside versus outside clothing (a bit like biohazard suits in those labs but probably more like a mechanic’s overalls) and increased use of “mud rooms” in housing.
I’m not yet sure how related this is to Wei_Dai’s answer, but found a medium article exploring “how far away to be from others who are walking in front of you”. It references a couple other non-english articles, and one english… translation (I think?) on urbanphysics.
Some researchers ran computer modeling of what happens to saliva
There is a critique of this here. I haven’t yet read it thoroughly.
This suggests to me that we don’t just want to consider distance. Time and speed are both elements here too. I think that is actually something people can understand intuitively if they get some basic information. Most people are not challenged with knowing where they need to be to catch the fly ball. Here they just need to have a reasonable sense of where not to be.
So the message really isn’t X distance but several factors that can include a distance metric.
However, the other aspect here is not safe (pick you metric) versus not safe. It’s about level or risk and what that implies about actions to take. This could be anything from what types of PPE one uses to thinks like everyone adopting inside versus outside clothing (a bit like biohazard suits in those labs but probably more like a mechanic’s overalls) and increased use of “mud rooms” in housing.