When one powerful man comes to visit another powerful man, there's certain to be a lot of irritation among people with less power, as many in downtown Washington have discovered this week when they have gotten caught up in what's known as a Movement.

A Movement is that vulnerable time when people such as Soviet President Mikail Gorbachev are going from one place to another. From a security standpoint, they are the most dangerous moments. Logistically, they're a nightmare.

"In, out, in, out. Open it up, close it down," one police official said in describing what a Movement is all about. And anyone who was on the streets downtown yesterday or Thursday most certainly was affected by the many Movements of the Soviet leader.

Signs of a Movement appear at least 30 minutes in advance. Without warning people who were walking or driving are forced to put their lives on hold.

The corner of 17th Street and Pennsylvania Avenue NW is a particularly likely Movement vortex as Gorbachev travels from the Soviet Embassy at 16th and L streets to the White House.

First the sidewalks close. Yellow police tape is strung. People caught in this Phase I of the Movement tend to blame themselves when they realize their paths are blocked. But some sort of momentum carries them forward to confront the police.

They explain their personal circumstance, claim emergencies. Then they show some sort of identification; everybody in Washington has one.

"Everybody's important," the police official said. "It's enough to drive you crazy."

During one Movement Thursday, CBS correspondent Lesley Stahl flashed credentials that allow her onto the hallowed grounds of the White House. Not good enough, police said. Not during a Movement.

Steve Jewel, a lifelong Washingtonian, got caught up in a Movement. Forced to backtrack, Jewel's irritation turned to amusement. "I don't enjoy walking four blocks out of my way, but that's the nature of living here," he said. "It's kind of neat when you think about it."

However, most people don't find it entertaining, especially when Phase II goes into effect, as much as 15 minutes before the Movement. A police sergeant orders the streets cleared, and no one is immune.

"You got to get out of the way," one police officer told the driver of a patrol car that had pulled over at 17th and Pennsylvania.

When the Movement begins, when the motorcycle engines are throbbing, when the motorcade zooms by for those three seconds, the Movement no longer is an inconvenience. It's exciting.

People so eager seconds earlier to get on with their business suddenly lose composure and start yelling: "Hey, Gorby, over here!"

"We saw him and he waved," said Pat Nealy, caught up in one Movement. "That man thinks {Gorbachev} waved at him, but he waved at us."