“SouthWest Transit is definitely forward thinking, and this is where things are headed when it comes to mobility,” said Darnell Grisby, director of Policy Development and Research for the Washington, D.C.-based American Public Transportation Association. “Now the transit user can be as spontaneous as the auto user has been in the past.”

Studies have shown that people are less likely to use public transportation if they are more than a mile from the nearest transit station or bus stop. SouthWest Transit launched Prime in July 2015 with the idea of helping passengers complete the “last mile commute.”

Over time, Southwest has expanded its fleet of 12-passenger vans from three to 11 as the service has caught on. In August more than 5,300 riders used the service and since then monthly ridership has continued to top 4,200 people — students, seniors and those who don’t own a car or choose to leave the one they own in park. They’ve used the service to get from their front door to work, doctor’s appointments, shopping and social engagements, paying just $3 a ride with cash or a credit card.

“It has just exploded,” said SouthWest Transit CEO Len Simich. “The general public has really taken to it.”