I'm a serving officer.
The physical tests are not that hard if you're reasonably fit. You need to be strong though because most of the people the police deal with tend to want to fight back.
Can you stand dead bodies too? Trust me, they're not pretty and they reek most of the time. You'll have to search them, strip the clothing at the mortuary etc.
As for traffic, you'll need a blues permit first and you won't get that for at least 2 years if you're in a town or city. Once you've then got that, you'll need to prove yourself with that permit and show competence at handling traffic matters. So bank on a MINIMUM of four years before realistically being able to apply for traffic.
Dog Handlers?

That is a dead mans boots job. You need to be vastly experienced in all areas and have the ability to stay in post for the life of the dog. So you may as well scratch that one from the list for years!
As for joining, your call. You'll suffer frustration due to the kind of people you'll deal with, frustration with the public. It's physically and mentally demanding, more that the public care to realise.....but, I wouldn't change my job for the world. I enjoy what I do.
Good luck