Start attending public traffic planning meetings. I can't say what they are called where you are, but they exist. Call your local government and ask. Pay attention to the notices in your local paper (in Columbus, they tend to appear in neighborhood newspapers). They may be ad hoc committees looking at specific areas, but if you regularly show up at meetings (and stay polite) you can have a lot of influence.
Once you learn where to go, show up and bring constructive solutions. Realize that you will likely be in for a multi-year struggle for anything worth doing.