Like all really great plans, allowing bicycles on the Metro system began as wishful thinking.

Now that it's heading into reality, let's all just grab our 10-speeds, roll down to the nearest subway stop and hop on, right?

Not so fast, bike enthusiasts.

Even a harmless, health-promoting machine like a two-wheeler can be a dangerous piece of equipment in the hustle and bustle of Metro traffic.

Who, after all, would appreciate getting mowed down on the escalator, or having his (or her) briefcase caught in somebody's spokes?

That's why Metro Planning wants to make sure that those who take part in the program, planned to last from June 6 to November 29, do so with safety and consideration.

To this end, those who wish to carry their bicycles on the subway are required to have a permit to do so, obtained only after attending a safety training session. Interested participants should call Metro Planning (at 637-1116) and make an appointment.

Most of the regulations, of course, involve common sense:

Bike-carrying passengers will be allowed to use only elevators, not escalators, and there'll definitely be no riding up and down the platforms to pass the time between trains.

In addition, Aikens says, bikers will be allowed to use only the last car of any train, and then only the two end sections of that car, with two people at each end. In other words, only four people per train will be allowed to carry bicycles.

Furthermore, bike-carriers must wait for trains at the rest of the platforms, so that pedestrian traffic will have a fighting chance of getting aboard trains without danger of getting a handlebar in the gullet.

Metro Planning wants this program to run as smoothly as did the demonstration it held six months ago, says Aikens, adding that "You can really hurt someone with a bicycle if you're not carefully following the rules, and we certainly don't want that to happen.