I think it depends heavily on the city and the way the roads have been planned. There are places where cyclists most definitely do slow down traffic, and that c

I think it depends heavily on the city and the way the roads have been planned. There are places where cyclists most definitely do slow down traffic, and that can be pretty unsafe for the cars. Houston, where I live, is an example. I don't dislike cyclists at all, but when a long string of cars encounters a single cyclist going at half the speed, at most, it really does cause problems. There are no bike lanes here and it's illegal to bike on sidewalks, so cyclists have no choice but to ride in the middle of the lane. What happens is, if there's enough traffic, a single cyclist can cause a mini traffic jam, because every car will try to switch lanes so they can pass, but there are too many cars for everybody to safely switch lanes. So one lane basically comes to a stop behind the cyclist and the other doesn't go much faster because of people trying to merge into it (which isn't safe due to the volume of cars). This is far from the worst situation that can happen on the road, but this is what happens with probably 90% of the cyclists I encounter in Houston while driving. In a city like Houston where everything is spread out, it is truly not practical to reduce all car speeds down to bike speeds.