A flash flood in the eastbound lanes of I-394 during Tuesday's morning rush hour brought traffic to a halt and prompted the Minnesota Department of Transportation to make an unusual move. The agency opened the carpool lane to all drivers, not just vehicles carrying two or more people, buses, motorcycles and solo motorists who agree to pay a fee to use the special lane.

Flood waters collected under the Penn Avenue overpass after heavy rains fell between 7 and 8 am. The standing water forced MnDOT to close two of 394s three lanes during the peak of rush.

Gridlock ensued and traffic stacked up through three suburbs back to near Ridgedale Center and I-494 in Minnetonka. At the request of the State Patrol, MnDOT waived fees for all drivers and opened the high occupancy toll (HOT) lanes in an effort to get traffic moving.

But drivers apparently didn't get the message, even through the overhead signs told drivers to use the HOT lane. Signs above the HOT lanes marked with a diamond displayed the word "open," the term MnDOT uses to let drivers know the lanes are open to all drivers and can legally be used for free.

"They don't know what open means," said Bobbie Dahlke, a spokesman for MnDOT.

In Tuesday's case, those who knew what "open" meant and took advantage sailed into downtown and saved upwards of 30 minutes while those who didn't sat nearly motionless on the gridlocked freeway.

There was no immediate word if MnDOT might consider using another term such as "free" to indicate when fees are not being collected. "No toll," however is not an option, Dahlke said.

"We don't like the word toll because that conjures up the image of throwing coins in a bucket." she said.

For the record, the HOT lanes on I-394 west of Hwy. 100 are restricted to carpools, buses and motorcycles and toll-paying drivers from 6 to 10 a.m. and 2 to 7 p.m. on weekdays.They are open to general traffic outside the tolled hours, such as on weeknights and weekends.

The reversible HOT lanes east of Hwy. 100 to downtown Minneapolis are tolled 24 hours.