The CTA is having trouble with large gaps in its bus service, according to performance metrics released this week.
From April through November, the agency did not meet its monthly target for the amount of time between two buses on a route, according to a November performance report. A CTA spokeswoman blamed the shortfall on the five-month southern Red Line overhaul that required multiple shuttle buses to ferry riders to the Green Line and other stops.
"You get one traffic jam and it causes a ripple effect," CTA spokeswoman Tammy Chase said. "That project's impact [is] gone and hopefully that number will be closer to normal."
The formula for calculating the CTA's monthly bus interval target is counting the number of bus intervals that are double the scheduled interval or longer than 15 minutes and dividing that number by the total number of weekday bus intervals traveled during the month.
The CTA's monthly target is 4 percent. From May through October, the time of the Red Line South project, that number exceeded 5 percent. In November, weeks after the Red Line project was complete, that number was 4.8 percent.
The CTA blamed the November shortfall on the Hot Chocolate 15K/5K road race downtown, the Magnificent Mile Lights Festival and the Thanksgiving Day Parade, events that all required bus reroutes.
The CTA has not been meeting other monthly bus targets. From August through November, the agency exceeded its target on bus bunching, when two buses arrive at a stop in rapid succession.
Also in November, the agency had 16.4 percent of its bus fleet unavailable for service, exceeding its 12.6 percent monthly target. The CTA said in November it began a new inspection process that affected how and when it took vehicles out of service.