Check to see if you need to /can schedule the shuttle. As mentioned it usually coordinates with the airport run (if close enough) or runs to local businesses who tend to have frequent guests. So sometimes the morning and evening rush hour is busy with trips to local business parks. Dinner and shopping trips are common. Tipping especially appreciated when you ask the driver to wait if you are picking up take away, need help loading shopping bags, or tie them up during rush hour traffic.