Thanks, loril54!
It seems to me that what happens more than once (though I can't cite episode numbers for you) is that somebody drives into town from Collinwood and gets a lift back from somebody else, leaving the original car stranded.
Do you mean up to this point?, cuz this is how I'd track the trips back and forth so far:
#1 - Vicki rode in Burke's limo to the Inn and took a cab to Collinwood
#2 - Joe and Carolyn are at the Blue Whale together and he drives her home
#3 - Roger drove into town, Joe drives back to the bar alone, and Malloy is in town
#4 - Roger has driven back home
#5 - Sam is on the Collinwood grounds
#6 - Sam is back home, Carolyn tells Vicki about the bus into town
#7 - Roger and Vicki got into town separately
#8 - Joe drives to Collinwood, Vicki returns with Carolyn's keys
#9 - Malloy leaves town and heads to Collinwood, and Carolyn asks to ride along with him on his trip back to town
#10 - Burke drives Carolyn home
#12 - Roger is back home
#13 - Burke leaves Collinwood alone
#14 - Burke and Joe are in the Blue Whale, Joe heads to Collinwood to pick Carolyn up and they end up at the Blue Whale
#15 - Roger crashes on the way to town
#16 - Bill and Roger are at the M.D.'s office, Joe leaves the bar and Burke follows after him with Carolyn in tow
#17 - Bill drives to the crash site and then back to the office to bring Roger home, Bill drives back to town
#18 - Roger and Vicki leave for town together
#19 - Malloy checks around town for Carolyn, Joe brings her home
#20 - Roger pulls up at the Inn with Vicki, and they return to Collinwood together