The nightmare commute scenario that many feared after Sunday's East Bay freeway inferno still had not materialized by Wednesday, with many motorists opting to take public transit rather than drive.

Traffic congestion was down Monday and Tuesday. The amount of time drivers were stuck in traffic moving slower than 60 mph was down 8 percent around the entire Bay Area, according to Caltrans data. Congestion on Oakland freeways, meanwhile, was down by more than 50 percent, the data showed.

Traffic on the Bay Bridge was down between 18 and 14.5 percent early this week. Some commuters may have taken other bridges -- on Monday, for example, the San Mateo Bridge saw an 8.6 percent jump in traffic. Yet by Tuesday, only very slight traffic increases -- less than 2 percent -- were seen on the San Mateo, Dumbarton and Benicia bridges.

BART ridership, meanwhile, spiked dramatically, hitting an all-time record on Tuesday. The number of BART commuters was up 10.4 percent Tuesday and 5.2 percent Wednesday morning; no figure was available for Monday, when fares were waived.

"I can only assume that people are using a variety of different ways to get where they are going, and apparently very efficiently,'' said Bob Pryor, a producer at the broadcast traffic reporting service Metro Traffic.

"I thought there would be huge backups on the Bay Bridge,'' Pryor said. "We've still got our fingers crossed. This is early in the process."

There were fewer cars on the road, and those that were there seemed to be traveling earlier, according to data collected by Berkeley Transportation Systems, a small company that analyzes freeway-flow data for Caltrans.

"It doesn't seem like travel times were getting worse; in fact, in some cases, they actually seemed to be getting better," said Karl Petty, an engineer who heads the company.

Petty said a small percentage of drivers staying off the roads can make a huge difference in lowering traffic congestion -- not just at the freeway collapse site, but around the region. This week's changes by a few drivers along key routes seemed to make a big difference, according Caltrans data from thousands of buried freeway sensors.

On Monday and Tuesday, the number of miles traveled by Bay Area drivers dropped very little -- about 1.7 percent, according to state traffic data. But along the affected routes the decreases were much higher.

Usually on weekday mornings, about 30,000 cars pass along the section of Interstate 580 going toward the MacArthur Maze. That westbound stretch is unaffected by the freeway collapse. On Monday morning, nearly 7,000 fewer cars passed through that stretch -- a drop of 22 percent. The volumes dropped by 15 percent on Tuesday and 11 percent on Wednesday, according to data from Caltrans' Freeway Performance Management System.

"Getting rid of 10 percent of the traffic can totally eliminate the congestion," Petty said.

On Monday and Tuesday, traffic on seven of the region's bridges fell roughly 6.8 percent compared with the four week average, with about 21,000 fewer vehicles passing through toll gates than the previous week, according to the Metropolitan Transportation Commission. Data on the Golden Gate Bridge, which is operated by a separate agency, were not available, although officials said there was no noticeable change in traffic.

Traffic across the Bay Bridge dropped most sharply, down Monday by 18 percent and Tuesday 14.5 percent, with 22,601 and nearly 17,000 fewer vehicles, respectively, versus the week before, said MTC spokesman John Goodwin. He did not have data from Wednesday. Usually around 130,000 cars pass through the toll plaza each day.

Traffic was noticeably heavier on the East Bay surface streets that have served as detours around the two damaged eastbound ramps in the maze. That congestion is particularly apparent in the evening, but local police said it was not severe. City officials estimated this week that an extra 5,000 cars an hour were streaming onto local roads during the evening commute.

Oakland retimed some intersection signals to protect pedestrians, and has asked Caltrans to arrange for crossing guards near several schools.

BART carried a record 375,200 riders on Tuesday, up from an average weekday of 340,000 riders. AC Transit did not show a similar spike.

BART's ridership fell back a bit Wednesday morning, with 7,300 more riders than average, for a total of about 140,000 riders who boarded from the start of service to 11 a.m. During roughly the same period on Tuesday -- the start of service until noon -- 158,000 people boarded BART -- an extra 13,000 riders, 9 percent more than usual.

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