Barring massive loss of infrastructure, taxis, buses, and privately owned vehicles are still viable. Paper bus schedules and taxi listings, cash on hand, good shoes, and a comfortable pack will handle most situations. The snag will be that with an unexpected large area event (i.e. 2011 Southwest Blackout), everybody will be scrambling for the same limited resources at the same time. Since these events commonly involve loss of power, you will not be able rent a car, get cash from an atm, or use a credit card.

That is where bikes, scooters, etc. will come into play. With your office space constraint (I'm assuming you're cubical rat like me), a folding bike or scooter stored under your desk may be a good solution. The downside is that these are not cheap (~$300), and the increased speed translates to increased risk of injury.