It's a fair question, but it's also very broad. I think if we steered you towards specific models, we might give you information that's too narrow for the time being.

There are so many different classes of bikes now. I got into cycling heavily in 1975, and there were not as many classes of bikes then. I think a lot of the distinctions are unimportant, but so many people are led to believe that they are important. Clearly, I disagree. You can look at mountain bikes, so-called hybrid bikes, road bikes, etc, and some will claim that one of these classes is ideal for commuting. The truth is that pretty much any bike will do very well.

Generally, wider tires are more comfortable than narrower tires, and they protect the rims from damage, especially if you're not meticulous about maintaining your tire pressure. If you're not riding off road, you don't need heavy tread on your tire. Heavy tread, such as with knobs, slows you down unnecessarily. When I ride with my wife, who is not nearly as fast a rider as I am, we ride mountain bikes, but both of our bikes have narrow, slick tires, for riding on the road. A mountain bike equipped with these tires is a wonderful general purpose bike.

For commuting in heavy traffic and for short trips and stops and starts, I much prefer upright handlebars to drop (racing) bars. Upright bars make it easy to look behind you, and they generally give you quicker access to your brakes. Handlebars can be changed on any model bike, though this is a much more expensive modification than a change of tires, so your are probably best off buying a bike with the type of handlebar you like.

You can buy new or used. Old bikes work just as well as new bikes. I'm very active in the "Classic & Vintage" section of this board, as I'm a collector and amateur mechanic. Most of my bikes are 20 to 35 years old. Bikes don't go obsolete as quickly as cars do.

If you buy new, I suggest you budget at least $370 for a bike. This way, you can get a decent bike at a bike shop. I used to say bikes at department stores are complete junk. That's not always true any more, but bikes are still assembled incompetently there, so you still don't make out so well, in my view. Someone like me, with lots of experience working on bikes can do well there, because I could buy a bike and take it apart and put it back together right.

craigslist is a good source of used bikes, though you have to know what you're looking at. Most used bikes need work after you buy them, but if you're patient, it's well worthwhile. Some bikes on craigslist are terribly overpriced. Some of them are devilishly underpriced, only because the seller is unaware of what he has. Some of us here on bikeforums have hobbies of "flipping" bikes which involves buying underpriced bikes, fixing them up, and selling them. I've gotten into it lately. It's fun and rewarding, though there isn't much money in it, to be truthful.

I think there is a lot of advice on accessories you will want to have, here in this thread. Take a look backwards. Some pop to mind:

- fenders (aka mudguards)
- rack
- lock
- tools
- toe clips or other form of foot retention
- bell
- pump
- water bottle
- clothing for cycling

I highly advise you not to cycle far with your luggage on your back. Attach it to your bike. A backpack is uncomfortable while cycling, and it limits your maneuverability, too.