Some private van services, hired by local employers, take people to and from train stations, but you can't use those services unless you work for the companies that hired them. And think of malls as big parking lots for the railroad. Lots of rail stations are within a few minute's drive of a mall. Get the malls to agree to run shuttles between the malls and the rail stations. The malls get better transportation for their workers.
Residents get a place to park when they want to take the train.
And pitch to the malls that those people are more likely to shop at the mall on the way home from work if they are already there to pick up their cars than if they are getting off the expressway. Far too many people don't know that existing transit can actually meet their needs. You can get their by transit. Remember that the competition is a very convenient automobile, which I probably already own and whose cost I am thus probably not considering. Too often the idea is to provide transportation for people who can't afford cars.