It's the season of increased deer/vehicle accidents.
There are many factors involved in the increased deer movement. DNR Deputy Director Rachel Torbert says the open of the archery deer season coincides with rut and with the crops coming out of the ground, deer are in their most active season.
Keep the distractions to a minimum and watch the sides of the road for the reflection of headlights in the eyes of deer. Torbert also stresses if you encounter a deer, don't veer, slow down, and hit the deer. She says this may sound illogical but swerving to avoid a deer can be more dangerous than just hitting the deer head-on.
While many may think deer/vehicle accidents are a rural issue but it can happen anywhere as there are often urban deer populations that are also becoming very active right now. She also reminds that if you see a deer on the side of the road, there are likely more around.
dnr.illinois.gov has all the regulations about keeping a deer that you might have hit if you do not have a deer tag.