So what if someone decides to go more than 10, 15, 20, hell even 40 over. Where do you think it starts to get ridiculous? The engineers that design the roads use science and statistics to come up with the number, then err on the side of caution a little. It's not arbitrary. I think the question is whether or not the law is needed, but what the limit should be. I agree that sometimes a few miles over is okay, but there needs to be a point where the line gets drawn. The fine is supposed to deter you from doing it, with a byproduct of funding the cities needs, and yes, some pockets. On a sunny day, speed can still pose a danger. And you yourself may be a very safe driver, but can you confidently say that there aren't drivers that may not be as able?
As for taxes, without them, funding for many crucial departments would all fall short of functioning budget. I agree that distribution and tracking need reform. But we cannot take the good without the bad. Thats why we vote. Tax sucks, but it's a necessity. I have never heard of a realistic way to fit the bill if taxes are cancelled. If you can enlighten me, I'm on your side, because I dont like taxes either. But like I said, I feel it's a necessity...
I've been to Germany a few times, my brother was stationed there way back. Even the Autobahn has a speed limit in some parts... but I have severely digressed. And now.... 
On speed limits;
I live on the big island
I used to drive the old saddle road at up to 80 MPH.
the speed limit was 25 MPH.
I'm an average driver skill level.
One mistake on that old road is generally a totaled vehicle.
I easily did 120 MPH on I-5 and I-90 on my Goldwing motorcycle.
No harm, if a mistake was made I'd be the one to suffer.
In my local town the speed limit is 25MPH,
I do 20 MPH because of all the Jaywalkers.
Last thing in the world I want to do is talk to a cop,
after the EMT took a Jaywalker to the hospital.
Taxes I'll re-emphasize, I'm willing to pay taxes for the public
good, but not for some political agenda.
Most taxes here in Hawaii are political
agenda driven.
I've been to the Philippines and Okinawa.
Didn't drive off base in either place.
But from what I saw traffic laws are
pretty much useless.
One of my favorite songs is "I can't drive 55".
Be well friend.