Informal discovery requests sometimes work. If not you have use subpoena duces tecum and serve on police agency. You must also file the same with court. Make sure you have proof of service to present to court. This can be complicated. Get an attorney .
ANDREW ROBERTS CRIMINAL AND TRAFFIC TICKET DEFENSE ATTORNEY
First, there really isn't much discovery in a traffic case. Most officers don't even write a report, as the citation itself is generally the only written evidence. That being said, when applicable, you can request MVARS (dash-cam) videos, radar calibration logs, etc. But there is no magic treatise on this, that's why we spend 3-4 years in law school. If you have a genuine issue to fight here, you'd be most wise to consult with a good, local criminal defense lawyer and get some sound, experienced legal advice on your case. Most of us on avvo offer free consultations. Good luck.
The learning curve for you is going to take hours if not days, then you still have to go to trial and put on your case. More time, days, learning, cramming, grappling with speed, distance, obstructions, clear view doctrine, calibration of radar. Do you really want to take this on ? One phone call to a good lawyer and its done for you.