FOPA applies in this case. Make sure the firearmis unloaded, locked and nott within reach from the driver or anyone. Ammo must be stored seperated and also must not be within reach. If you are driving in a car the best place is your trunk. When I drive through NY, I stop before I enter and lock everything up then drive through the state then stop after I get out and load everything back up.
One of the law's provisions was that persons traveling from one place to another cannot be incarcerated for a firearms offense in a state that has strict gun control laws if the traveler is just passing through (short stops for food and gas) and the firearms and ammunition are not immediately accessible, unloaded and, in the case of a vehicle without a compartment separate from the driver’s compartment, in a locked container.[7]
Go to the state website and print out their rules, keep them in the car to show an officer if it becomes an issue.
No one's said it yet but under no circumstance do you volunteer that you have any weapons in the vehicle
Transport Your Firearm Legally - IL State Police Pamphlet
http://www.isp.state.il.us/docs/1-154.pdf