The travel time on BART from Powell to Coliseum stations is 23 minutes. BART usually runs right on schedule. The travel time on AirBART from Coliseum Station to OAK is approximately 12 minutes. The travel time on AC Transit Route 73, which also runs between Coliseum Station and OAK, also takes 12 minutes.
AirBART picks up directly in front of the Coliseum Station, on the west side of the exit area. AC Transit Route 73 picks up across the street from the west side of the exit area. The immediate station is fine; the neighborhood directly east of the station (other direction from the bus loading area) should be avoided.
BART and AirBART information is available here: www.bart.gov/guide/airport/inbound_oak.aspx
AC Transit Route 73 information is available here: http://www.actransit.org