Excess of police and security in D.C.?

I've been in D.C. for only a few days now, and I'm puzzled by what seems to be an inappropriate excess of idle security guards and police patrolling the streets, more than anywhere else I can recall. My hunch, without any numeric data at all, and with a libertarian bias, is that this is an inefficient allocation of resources. I suspect that there are far more security guards and police officers supplied than what might be a market demand for them. I can imagine some bureaucrats making the decision to hire more and more police and security guards as a way of curbing unemployment in the city, because this is the capital, and they have the funds from the taxpayers. I don't know whether local services such as police are funded purely though local taxes, but I would guess that security guards for federal buildings are paid with federal dollars. I can understand why local police might be federally funded.

Just minutes ago I was bewildered as a police officer sat down in his car, then immediately, within seconds, turned his lights on and pulled over a car that was passing by. Maybe I didn't notice if this car ran a red light or was missing some easily noticeable required sticker, but if it were neither of those, the officer's decision to pull this person over was too fast to have checked the speed or run the plates.