Well, instead you might incentiveise it through having car pool car parks that are closer to campus, or at least next to a well lit and preferably sheltered area. Then you could publicise the car pool scheme. You could even have a forum for finding other car poopers, and/or an app. Maybe allow people, with their consent, to be matched by approx origin/destination for easier finding.
If you had a computer science or math department then I'm sure they would have people who could solve the ride matching problem.
Given that there often is a bus or even many buses, the question then might turn to "Why do people prefer their cars to a bus?". And now we're back at the beginning.
The disconnectedness of suburbia is at the heart of this, but essentially insoluble in the short term.