When the power went out in a broad swath of the Upper East Side and the Bronx on Wednesday, a record number of commuters turned to the Internet to learn if their subway lines or commuter trains were running. But the Metropolitan Transportation Authority's Web site provided no help.

The site became inaccessible shortly after the electricity went out at 3:41 p.m. and was down for about an hour, a little longer than the 49-minute power failure.

"Because the incident occurred right before people were getting ready to leave the office, we had a huge surge of traffic at one time, unlike anything we'd had before," Jeremy Soffin, a spokesman for the transportation authority, said yesterday.

The failure cut power to signals on several subway lines. Service was disrupted, with delays extending well into the evening, making the trip home for many commuters even more uncomfortable on a hot and muggy day. Service on the Metro-North Railroad was also briefly interrupted.