South County commuters who want to try the rail service at Wickford Junction in North Kingstown can do so for free on Wednesdays this winter. The state Department of Transportation and Governor Lincoln Chafee announced a program Thursday to encourage people to try the service. Service started in April and has so far drawn daily ridership of about 150. The program will run six Wednesdays, from Jan. 23 until Feb. 27. Commuters will get free parking at Wickford Station and a round-trip ticket to Providence. The offer is valid until 3 p.m. and riders must download a registration form at wickfordjunction.com to participate.