ST. LOUIS • Heading east downtown, Bruce and Sara walk side by side, looking straight ahead. A block away, also headed east, Julian and Kiera stroll in tandem. In the real world, the four LED figures have not moved an inch from where they were installed 2½ years ago in Citygarden downtown.

But in an imaginary world, two of the figures have walked more than halfway around the world, and the other two are getting close to that point. Together, the four have logged more than 100 million steps since becoming art installations.

This exercise in imagination came with the cooperation of London-based artist Julian Opie, who created the two pieces, formally known as "This is Kiera and Julian Walking" and "This is Bruce and Sara Walking."

At the Post-Dispatch's request, Opie's studio staff calculated the number of steps each figure walks per minute and each of their strides.

Combining those numbers, walker Julian breaks away from the other figures. So much so that he will return to the Citygarden seven months ahead of Kiera, 14 months ahead of Sara and 20 months ahead of Bruce in the simulated journey.

The four-year trek around the world for Julian demonstrates just how leisurely a pace the figures are walking. The average person walks about 3.5 miles an hour; Julian is averaging just over half a mile an hour.

But LED figures have no needs for bathroom stops or food breaks. And in this globetrotting trip, we are presuming the Earth is flat and the figures are walking at sea level. That wipes mountain ranges, oceans and other topographical challenges off the map.

WALKING DUE EAST

On this expedition, all the figures are walking due east from downtown St. Louis, always staying between the 38th and 39th parallel (the latitude of 38.627 North, to be exact).

Along this path, the Gateway Arch became the Gateway to the East as the walkers began their journey across the Mississippi River into Illinois and through parts of Indiana, Kentucky, West Virginia, Virginia and Maryland.

Once across the Atlantic Ocean, the walkers passed through southern Portugal, the Sierra Morena mountains in Spain, Sicily and the foot of the boot of Italy. They continued through Greece and parts of the Middle East including the northern tip of Iran and the Caspian Sea.

It's just past Turkmenistan that we catch up with Bruce, who is in eastern Tajikistan, a tiny mountain country. It sits just north of Afghanistan and Pakistan.

JULIAN IS QUICKER

Nearly 700 miles ahead of Bruce, Sara is making her way through the Taklimaken Desert in northwest China. Ahead of her by not quite 1,200 miles is Kiera, who is just east of Yinchaun, China, a city of about 2 million. Julian, meanwhile, has already crossed the Yellow Sea, through North Korea and South Korea, and is about 100 miles off the western coast of Japan — and 3,500 miles ahead of Bruce.

At first glance, the four figures at Citygarden appear to be walking at about the same pace. But a closer look shows that Julian walks at 24.2 steps per minute while his walking mate, Kiera, logs 22 steps per minute. Over the course of an hour, Kiera would fall 132 steps behind Julian. In the other art piece, Sara is walking at a faster clip, at 21.4 steps per minute, compared to 19.2 for Bruce. Like Kiera, Bruce would fall 132 steps behind his walking mate over the course of an hour. That's why, 2½ years later, there is such a great distance between them on their global walk.

Opie, the creator of the popular works, does not typically do interviews. Like many artists, he'd rather let his art speak for itself. But he and his London studio staff were intrigued by the inquiry and calculated how many steps each of the figures have taken based on their pace. Opie said by phone that he had not considered the simulated distance of the walkers.

But he studies movement of people in making his art, often standing on street corners and watching the faceless crowds moving at different paces toward directions unknown. Wondering how far his figures would stroll over various periods of time makes sense, he said.

Opie has not been to St. Louis to see the installations, but he says both the stillness and motion that the pieces represent fit nicely into a place where people come to stroll, or just watch the art do it.

A SUBLIMINAL HINT

A former arts critic for the Post-Dispatch said the positioning of "This is Bruce and Sara Walking" at a main garden entrance on 10th Street provides a subliminal hint to visitors: Come on in and enjoy yourself.

The pieces are among 24 sculptures in Citygarden, all owned by Gateway Foundation, the entity that created the popular downtown spot. The foundation was asked to join Opie in playing along with the simulated journey. Foundation Director Christy Fox declined.

But art experts were more than happy to join in.

"What I love is the relatability of his work to the public," said Tricia Paik, assistant curator of modern and contemporary art at St. Louis Art Museum. Opie has taken traditional sculpture, often done in bronze or marble, and "made a flat interpretation, making it of our time using electronic media."

Marilu Knode, director of Laumeier Sculpture Park, said the joy of art is "finding a different way to understand it." A simulated walk around the world can symbolize "human life and the struggle for moving forward in your world when there are so many things that prevent us from moving forward."

Opie said the 'slightly fiery" glow of the amber LED gives off an authoritarian tone. LED lights of similar color are often used in highway light boards or pedestrian crossings, instructing us to stop, buckle up, slow down, detour.

In this imaginary journey, there will be no detours or signs offering caution. The walkers will trudge along at their own perpetual paces. As of Sunday the foursome has completed 949 days of walking.

At their current stride and steps per minute, expect to see Julian return to the Citygarden on Aug. 6, 2013 — four years, one month and five days after departing.

Maybe there will be a simulated welcome-home party.