Coming SE --> NW through Chicagoland, you start off with 80/90. Then 80 leaves 90 and joins 94. Then 94 leaves 80 and heads into the city where it joins 90, and at the same spot where 94 leaves 80, 294 joins 80 for a few miles, then they split. 90 and 94 also split apart north of downtown.
This is of course why the locals all call roads by names instead of numbers, but it can get confusing for people passing through or new to the area.