At about 3:30 p.m. the tourmobile "Martha" ran into a car parked beside Dianna's Caribbean Cooking Mobile, but the thousands who crowded around the stage on the Ellipse didn't miss a beat.

The sixth annual Caribbean Festival was cooking. Aficionados of reggae, salsa, steel bands and African drums pulsed to a stew of rhythm dished out by such groups as the Trinidad and Tobago Steel Orchestra of Baltimore, the Asafo Dancers and Drummers, Premier, Choc and Los Hijos De Adolfo Sax.

Emcee John Blake, who was on hand to broadcast the festivities on WHURFM, spiced the afternoon's proceedings with exhortations to the crowd. The response was deafening.

With the exception of the two dozen tourists, sitting with chins on hands in the marooned "Martha," most of the crowd was dancing . . . or at least tapping their feet.

"I dance because it feels good," Adisa Akil of Washington confessed during a rare moment when he wasn't in and all around the air to the right of the stage. "I dance whenever I can."

His leaps off the ground quaking with rhythm were infectious. Soon a bearded fellow in a saffron robe was leaping right beside him. Then Penny Richards, Margo George, Richard Brown and the "Mysterious Lady" folded the parasol that wasn't much protection from the hot-hazy heat, leapt up from their blanket and cooled the hot air with their movements. Next to them Karrem Jackson took time out from his fourth birthday party to shake a leg.

To the left of the stage, away from Akil, the action was more subdued.

"When it gets cooler we will dance, definitely," Mark and Susan Wisniewski, who came down from Adelphi for the Festival, promised as they slouched next to their cooler. "We're here with our friend from Trinidad."

Trinidad was much in evidence. As the steel orchestra from Baltimore played their orange drums, the Trinidad Steel Band of Washington arranged their red drums in front of the stage.

Behind the packed grandstands where many were executing the sitting reggae, Dianna's mobile restaurant was serving a bit of that island's cuisine.

"I used to eat this a lot in Brooklyn. It's roti, curried goat in unleavened bread," Harvey Miller explained. "I had to stand in line a long time to get it. But it was worth it."

One would have liked to know how lau, yams and cabbage, all West Indian style, Dianna's might have served, but they were too busy dishing it up to talk about it. After first feasting the many performers who were donating their services for free, Dianna's had to deal with long lines all afternoon. Their waiters didn't even have time to dance.

Neither did the two park policemen who came to the scene to get the stranded tourmobile on the road back to the Smithsonian. They were none too soon. A touring fireman from Delaware glumly said that he didn't enmuch shrimp, beef, chicken, goat, pejoy the 45-minute wait behind Dianna's and the Caribbean experience at all.

His was a minority report.

"Last year we had the festival at Malcolm X Park, and it was very successful," Roland Barnes, one of the organizers and also a performer in the Carifolk Singers group, said. "But here at the Ellipse people have greater access to us and to the culture we want to share. We hope to be here every year. Say, why aren't you dancing?" CAPTION: Picture, Caribbean dancers on the Ellipse; by James A. Parcell - The Washington Post