CARTA carried more than 4 million riders in 2008, an increase of about 20 percent over 2007 and one of the bus system's busiest years ever.
Each month in 2008 there were more passenger trips than during the corresponding month in 2007, according to the Charleston Area Regional Transportation Authority.
The popular and largely employer-subsidized Express Bus routes accounted for a significant part of the increased ridership in 2008. High gas prices last year also drove more commuters to public transportation.
"Ridership of this magnitude reinforces that CARTA continues to grow and improve," said Howard Chapman, executive director of CARTA. "The implementation of the commuter Express Service in January 2007 has contributed greatly to the ridership increases CARTA has been experiencing."
The College of Charleston and the Medical University of South Carolina provide free bus passes to students and staff, and the institutions, in turn, pay a lump sum to CARTA. In September, MUSC said it had 1,400 regular Express Bus riders in June, compared with just 150 in February 2007.
The bus system hadn't seen last year's level of ridership since 2001, which was the only year CARTA carried more passengers.
Like most mass transit systems, CARTA counts everyone who boards a bus as one rider, so one person commuting to work five days a week, 50 weeks a year, would be counted as 500 riders for that year.
The strong ridership numbers for 2008 are seen as a sign that CARTA has largely recovered from 2004, when bus service was cut by 75 percent and fares were raised after the state Supreme Court upheld a challenge to the 2002 half-cent sales tax referendum in Charleston County. That year, ridership plunged to 890,417, from nearly 3.2 million in 2003.
Voters came to CARTA's rescue in November 2004, approving a revised half-cent sales tax that funds highway projects, green space purchases and a portion of CARTA service.