There are a few distinct advantages to using a bicycle as a bug out vehicle.
They are infinitely more portable and lightweight than a car or truck. Thus, you can store them in a basement or storage locker without much effort.
You can find them very cheap, even free, if you look around. Rummage sales, Craigslist, Freecycle, even friends or neighbors are great sources for cheap or free bikes. Many police departments sell off bikes they recover but go unclaimed. You can easily get enough bikes for a family of five for less than say thirty bucks. Clean them up, spend a few bucks on new tubes, and you’re good to go.
A bike is much more maneuverable than a car or truck, able to fit through the smallest gaps on the roads as well as going down trails barely wide enough to walk on.
Bikes are free to operate, requiring no gas, electrics, or oil (beyond lubing the chain and such periodically). Thus, the bike is pretty much EMP proof.
However, this brings us to one of the big downsides–YOU are the engine. While most of us learned to ride a bike when we were young, if you’ve not been on one in many years, be prepared for a rude awakening. It takes some time to get conditioned to riding a bike again. Just like any other form of exercise, you need to condition yourself.
Bikes can carry a surprising amount of “stuff” in bags of various configurations. But, since you’ll be the one moving all that stuff using pedal power, every ounce is felt.
You might consider as well using a bike just as a means of transporting your gear–loading it up and pushing it instead of riding it. You can carry a lot more weight that way, but obviously you’ll be walking instead of riding, thus moving slower.
Give some thought to picking up a cheap bike as transportation insurance against EMP if nothing else. Don’t worry, you’ll quickly remember how to ride it. After all, it is like riding a bike, right?