It could be either or! Yes, there is a program that allows people to "ride along" with police officers. The individual has to sign a waiver of non liability for the police department so you can probably call the main patrol office and ask who was the ride along for so&so on such&such night (and probably should have done this before confronting your boyfriend). He would be incredibly stupid to drive around with a woman just for kicks (or sex!), it's all too easy to get caught doing such a stupid thing. On the other hand, cops have the highest separation/divorce rate of all occupations because they egos the size of mansions. He may very well believe no one would ever catch him doing that. So if you want to find out for sure, call the police department and ask about the ride along. If he was lying, say so long with no regrets. But if it was legit, you've already damaged your relationship by following him while he was on duty and accusing him in public.  He may say so long with no regrets. Either way, I'd say you've lost.

You behaved badly and you owe him an apology.

Is it possible he's cheating on you? Sure. Anything's possible.

Is it possible he's telling the truth? Absolutely.

In either case, you have now proven yourself to be a crazy stalker nutcase type of a girlfriend - following him when he is at work and refusing to listen to a rational explanation.

If I were he, I'd dump you faster than I could turn around.

In my area, police are forbidden to have people riding in their squads unless it's for an official reason ( official ride-alongs;they are under arrest). We have no way of knowing if he was cheating, but neither did you. He could very well have been telling the truth.  Following him and accusing him were uncalled for and you come across as being  a jealous b****h I don't think calling the police department will accomplish anything: privacy matters would,I'm sure,  preclude them from giving you any information.    So, in answer to your question, I think your actions were crazy and you have no choice but to move on.

What do you not understand about the answers you've received? Is that why you acted like a crazy jealous nut and kept following your (now former) boyfriend while he was working?

You were out of line. Period.

Your boyfriend is a police officer. He was in his official vehicle during his work shift. As such, it is perfectly normal for him to focus on his JOB - not you.

Police officers lay their lives on the line every day. For you to expect him to immediately acknowledge you just because you happened to be where he was is ridiculous. What did you expect him to do, drive along next to you blowing you kisses? He was at work and in the presence of a (potential) co-worker.

Are you that insecure that you need his constant attention and adulation?

The woman with him was also absolutely correct in maintaining her composure instead of interacting with you. One of the first things you learn is NOT to make eye contact with someone who's acting off balance - as doing so may incite them to even worse behavior.

You were following your boyfriend and demanding answers from him for something that was not an urgent matter and could have been addressed during personal time - not at work.

You lost it and therefore you've lost him. Deservedly so. 

It could be because 1) he was on duty; 2) even though he appeared to be looking at you, he might have had other things on his mind and didn't even notice you; or 3)  he could have known how you would react. He might have had many other reasons that only he would know of; unfortunately, you probably are now in the position that you won't find out.

Confused & Tormented ,  After reading your second post I have a question for you , why do you even care ?  Why on earth were you with this man to begin with .  Read back to yourself the list of lies ,disrespect and deceit that your so called relationship was laced with .  You have no trust or faith in this man given his past history and his treatment of you .  You deserve better and you should be jumping for joy to have this man out of your life .  Let it go , move on , find an honest man you can build a life with filled with love , fidelity , respect ,honesty ,  the right man will only make you crazy about him and that's a good thing .