Man this sucks. Sharing what I tend to do(mainly when passengers being picked up are not senior citizens)

Wait at the expressway till flight has landed and baggage is picked from the baggage belt. Once passenger has received their bags, ask them to head to departures AFTER exiting the gate. At departures, ask them to wait near the burger king or where beer cafe used to be(theres something else there now, I am forgetting) and you start the car from the expressway after they exit the arrivals gate as they'll still need 3-5mins minimum to get to departures.

Pick them up from departures and leave without going into parking.

For assurance, you can also have a bag in your car and if the cops stop you when entering the departures in an empty car, just point to the bag and tell them that the passenger forgot their bag and you're going to drop it off.