There is a perception that cyclists tend to slow down other vehicles, mainly motorized, along roads. Again, such can be the experience of some that have been generalized and accepted as fact in most cases. However, if we look closely at the evidence, the perception may not be true for most cases after all. This article comes out of Portland State University:
Schaefer, J., Figliozzi, M. and Unnikrishnan, A. (2020) “Do bicycles slow down cars on low speed, low traffic roads? Latest research says ‘no’,” EurekAlert!, https://eurekalert.org/pub_releases/2020-07/psu-dbs072320.php [Last accessed: 8/1/2020]
Check out the wealth of information through the links found throughout the article that includes references to published material in reputable journals. EurekAlert! is from the American Association for the Advancement of Science (AAAS).
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Caught (up) in traffic 
Hi. I live in Portland so I agree somewhat with the research finding, although personally I tend to slow down whenever there is a cyclist on the road just for safety and courtesy. Our city’s bike lanes are ever expanding to cover more and more streets and neighborhoods. Thank you.