Your bike weighs <10lbs their car weighs >2 tons...YOU are ALLWAYS IN DANGER when riding on the streets. AND they are MORONS to boot.
That being said....
If you have to, load up and drive to a place where you can ride a measured distance over and over where the traffic is less stressful.
I 've trained at a "loop" There's an island nearby that has a loop that's about a mile and 1/2 circle and I can just go round and round as fast as I can go (up to the 25mph speed limit) I try to pass the cars if any show up there.
It's funny, some people get offended when you pass them on a bike. But I can't keep it up for long.
Try local city parks, national parks, nature preserves, wilderness areas etc... they usually have bike paths along the roads, usually have good roads, and low traffic.
Try to join a Bike Club...USUALLY they are open to teaching you the ropes of bike race edicate, drafting, etc... and will give advice on what to eat and what to wear.
As far as training I don't recommend adding more than 10% distance or speed each week. Break up long distance rides with several shorter faster rides (10% faster that regular pace) throughout the week. (I.E. have several 7 to 10 miles rides then one 20 to 30 mile Next week add 10% to the miles NOT the speed)
Make sure you REST a day or two after long rides. Remember, you are building up your strength for the long haul. If you don't rest and re-build, you'll burn out FAST.
For me, "GOO" works well as a supplement during and after the ride.(Lots of CARBS) I keep three taped to my center tube so all I have to do is rip one off and suck it down. I keep a few more in my back pocket of my jersey.
DRINK WATER. If there is an aid station with water I STOP AT EVERY ONE. I am NOT riding the tour de france and my name is not Lance... So, Stop long enough to sip a little water, and slurp down a "GOO" if it's time. I save the water bottle on my bike until I NEED it.