New York City ? The forecast is ominous: A small explosive sneaked onto a commuter train punches a 50-square-foot hole in a tunnel under the Hudson River. More than a million gallons of water a minute surges in. Flooding engulfs parts of the system within hours.

That worst-case scenario was included in a draft analysis of the PATH rail system linking New Jersey and Manhattan, obtained by The New York Times and reported in Friday’s editions. The analysis suggests the system’s tunnels, which serve 230,000 riders each weekday, are more vulnerable to terrorist attack than originally thought, and raised questions about whether officials have taken enough precautions.

Gov. George Pataki said he had received the analysis and called it part of an ongoing effort to look at security on regional transit systems.