Getting to downtown Chicago from Fermilab should nominally take you about 45 minutes to an hour by car, but that estimate can be complicated by the sometimes severe traffic in the Chicago area (do not go downtown during rush hours if you can help it). Once you get downtown, it may still take you a while to reach your final destination, so plan accordingly. The following sections give you some tips about getting downtown.
The City of Chicago is quite spread out, which combined with urban traffic can make getting around troublesome for the unfamiliar. You can listen to the radio for traffic reports - but note that they will refer to all the highways by their names rather than their numbers. A map of Illinois would have a name/number translation. Downtown Chicago, in the area referred to as the Loop (because the Elevated trains run in a loop around it), can also be very congested, and the many small one-way streets can be confusing to a visitor.
In Chicago, as in any large city, you should exercise appropriate caution, especially in unfamiliar areas and especially after dark. Many guidebooks recommend driving with car doors and windows locked; driving to a lighted gas station to ask directions or to look at a map; not walking in unfamiliar areas; and not riding subways at night except with a group.