Right to Life of Michigan in the past sponsored buses from venues around the state, but when it ran short of funds, "the initiative was thrown back on the local affiliates," Thomas said. That's when he learned of the many challenges involved in getting even a single busload of marchers.

"The vendors with whom you contract need payment, or firm commitment, by a certain date. But that date is usually well before the trip itself, sometimes as much as six weeks. We're finding out that a good number of people don't even think about registering for a bus until after Christmas," Thomas explained.

So if the sponsoring organization is counting on registration fees, "they won't have enough in time, and will have to cancel, just before people start calling to ask, 'Are you still sending a bus?'"

For this year's march, St. Clair County Right to Life raised enough money to fund the full trip in advance and do not have to worry about canceling the trip unless the weather conditions are too severe -- like last January, when a snowstorm stranded dozens of buses on the Pennsylvania Turnpike on the return journey.

The Venango County chapter of Pennsylvanians for Human Life, based in Oil City, faces a similar struggle.

"We have been taking a bus from the Oil City area for 36 years," said Judy Anderton, who heads the chapter. "We used to fill two buses, which included students from Venango Catholic High School. We are down to one bus and it is getting harder to fill."

The cost of the bus, she noted, "has gone from under $1,000 to about $2,600 this year, and it is getting harder to cover the cost with low passenger numbers. This may have to be our last bus."

Many bus trips from Midwestern states are nonstop drives of nearly 24 hours, but that usually depends on the average age of the group, Thomas said. "Because we're trying to accommodate an older base of registrants, we're doing a double-overnight stay, driving down the day before, spending the night, participating in the march on Friday, spending the night again, and driving back the day afterward. Ours is a very sparse trip -- no sightseeing tours, no extra time for shopping," he said.

The University of Mary group is making a nonstop trek. And they will be proud to do so, because march organizers selected them to hold the banner and lead the parade in their orange and blue knit caps.

"I think they noted the faithfulness of the University of Mary pro-life movement and our effort to support that," said Anne Dziak, a Chicago native and recent graduate of the university who now works as an admissions counselor at the school.

Last year, the university sent 100 marchers. This year, the number swelled with additions of pro-life groups from Bismarck-area high schools and groups from Fargo and Minnesota. It will take 14 buses to hold them all.

This will be Dziak's 12th march and the seventh time the university, which has an enrollment of about 3,100, has sent a group.

"We have a lot of practice staying warm," she said. The caravan will leave the morning of Jan. 25 and ride through the night to arrive in Washington at 3 p.m. the following day, giving them just one overnight stay.

She concedes that nonstop trips aren't for everyone, but said there are benefits.

"It's a good opportunity to allow the students to grow to know each other and make it more of a pilgrimage for us," Dziak said. She advised students "to take it all in. Some of the best conversations I've had are on the bus at 2 or 3 a.m."

March organizers do not announce attendance estimates, preferring to give the number only as in the tens of thousands.