It's best from a fortification point of view. If you're traversing massive spaces you're going to need rest and sleep or a home base if you're not going anywhere. There's wood panels and cinderblock everywhere. Cement is also in healthy supply as are powertools and axes for various purposes. You could outfit a truck with some easy armor without need of a mechanic. The most important thing, however, would be the peace of mind in sleep. You can actually be rested to make a run the next day to the next checkpoint.
If a virus outbreak of some kind were to occur (even if you're traveling by yourself) you'd need to pace yourself. Also, if the military napalms the city, you're surrounded by concrete. I'm sure there's some area somewhere with concrete walls that'd let you live the firestorm. Otherwise, you have building blocks, something could probably be figured out. The city is your oyster and Lowes or Home Depot are like fortresses. You can even use one of their many ladders to get to the roof to scope out the surroundings and the building can house many, many people without people who shouldn't be together causing trouble.
I always thought it'd be an interesting idea to create a travel network of them for survivors. An Underground Railroad for survivors, if you will. They're relatively safe compared to other structures. Zombies or infected aren't as much of an issue when three feet of wood and cinderblock are between you and them -that's assuming they even know you're there. The hard part would be the initial clearout of the said Lowes or Home Depot. Once cleared, you have a safe place to hang out after foraging. If they're not zombies, you could just outlive them 'cause they'd all starve -most likely. The behavior of infected would be a factor in how to make your play seeing as real-life infected may not act like the ones in movies or games so things could be more complicated, but you'd at least have a place where you could brainstorm without getting eaten. Time to think is priceless and invaluable to your life in a situation where your life (and possibly others) depends on your actions.
That, and if you really think about it... infected plague really isn't that ludicrous an idea. It's entirely plausible someone is trying to make a weapon like that. Literally, you could concievably decimate an entire country's population with a plague. Plague is the one thing that kills more people than years of warfare and we have NO adequate defense against it or WARNING. It happens quickly, it spreads quickly. Population dies off and other countries move in if there aren't enough survivors to defend themselves from attack. Something like that would be the ideal weapon against America. No one's dumb enough to attack us on our own soil in full force. The only reason terrorists get away with it is because they're not centralized in a way that we can attack. Vietnam on the other hand... they wouldn't even get close. They fire missiles, we shoot said missiles out of the sky and nail them so hard they don't get back up. They send ships, we sink them. Our geographic isolation makes us near impossible to fight not to mention we're a powerful militant country to begin with. A plague feeds on that isolation though. With an airline lock on the Americas, the virus would have little chance of making it to the country that released it. Terrorists could easily do the same. It's actually quite genius if you think about it, it could SO easily backfire though. The backlash of something like that would not be repairable and whomever uses it or creates it would have to keep that in mind.