If you're used to cycling you'll know that the worst enemies of the cyclist are the wind and rain. Sometimes a jacket is just too much to just protect us from the wind or rain. Here's where the cycle vests have a very practical function when trying to protect ourselves from a light wind or rain, as at the same time they ventilate as the arms are uncovered. Which is why the vest is one of the most practical cycling garments, as it protects the trunk area, being the part of the body that receives most wind.
And the best of all is that it hardly takes up any space for carrying, so it's easy to store inside your back pack or directly in the pockets of the jersey. Also, you don't need to worry about whether the vest covers your jersey or jacket, as there are transparent ones that proved a correct visibility even if you are wearing a number.
Another practical function of cycle vests is to improve visibility, which make them very recommendable for city cyclists, as their reflectors and fluorescent colours help other cyclists or drivers to quickly identify us. Either way, if you normally cycle in traffic, it would not be overkill to incorporate some kind of light on your bicycle, gear or helmet and thus avoid greater harm.
Are you from United States? 
