Hundreds of bicyclists, walkers and gawkers reveled a bit Sunday on the unopened stretch of Highway 40 in what was literally the calm before the storm.

Local residents were granted access to the brand-new stretch of the roadway from Ballas Road to Interstate 170 that was set to open at 5 a.m. this morning, some 11 months after it was closed for the first phase of the massive reconstruction.

Residents and officials celebrated partial completion of one of the largest infrastructure projects in St. Louis history — and something of a return to normalcy for drivers in the western suburbs. They brought bicycles, running shoes and canine companions out for a brief chance to enjoy the new pavement sans car. A 5K run, bike race, elite cycling time trial and marching band performance all marked the day.

But a wintry storm rolling in Sunday night brought the potential to snarl today's official unveiling of the new section of highway. The weather also promised to complicate the Monday morning commute for drivers affected by the closure Saturday of Highway 40 from Interstate 170 to Kingshighway for the next phase of the reconstruction.

The National Weather Service predicted as much as an inch of sleet and freezing rain by midday today, with snow possible through Tuesday. Given the forecast, salt trucks appeared likely to be the very first vehicles to drive the highway once officially opened.

State and local officials hailed the road's completion as a smooth success. The first phase of construction ended two weeks early and under budget.

"We're showing the rest of the country how to do big projects," said Missouri Department of Transportation Director Pete Rahn. "You do them right, get them done and get them done earlier than scheduled."

The novelty of walking, riding or say getting one's picture taken on an empty interstate seemed to be the most common reason to attend Sunday's shindig. Sharon Brahan of Rock Hill took a stroll from McKnight Road down to Brentwood for breakfast this morning because, "How often do you get to do something like this?"

"I wanted to be able to show a picture to my grandchildren of us," said Debbie Bunten, who came out with a friend from her house in Chesterfield. "I don't have them (grandchildren) yet, but years from now when they're on the highway and it's packed with cars, they'll think it's crazy."

Crazy is what Joe Wiss' kids called him for wanting to walk the interstate. The 73-year-old retired trucker enthusiastically hauled his wife and friends from the Dogtown neighborhood to join him for a constitutional.

"This is the first and the only time we'll get to do this," Wiss said.

Wiss reminisced about the days when that stretch of highway was little more than a hodge-podge of roads. He was a youngster in the 1950s, when the official Highway 40 would be closed at times near Hampton Avenue for soapbox derby races.

"It seems weird just standing here in the middle of the highway talking," said Wiss' buddy Rick Brine, a retired construction worker. (The kids, by the way, preferred to stay in.)

The roughly five-mile stretch of highway was an eerie sight early in the morning when only a few dozen people were out: long stretches of pristine, nearly white pavement interrupted only by the lone runner.

As the morning wore on, more and more people began to show up, some by shuttle bus, others by simply walking the on- and off-ramps. A midday temperature in the 50s with a strong breeze gave the day a decidedly un-December-like feel.

For Kevin Bailey of Brentwood, the highway provided a convenient if unique place to run his two yellow labradors. He otherwise would have found himself in Forest Park jogging, particularly with the good weather.

He joked that he and the dogs like the highway "better as a park" but then quickly said that he really can't wait for it to reopen. He expects his 40-minute commute from Brentwood to Chesterfield, where he sells medical equipment, to drop to just eight minutes.

Most everyone shared Bailey's enthusiasm at the thought of an easier commute. In a skintight biking outfit, Zack Stein, 17, sat atop his $12,000 bike waiting for the U.S.A. Cycling Time Trial to begin. He mused about not having to take a circuitous route from his home in St. Charles to St. Louis University High School every day.

Then again, the closure of the next stretch of interstate will alter his commute in a different way.

"Come to think about it, I have no idea how I'm getting to school Monday," he said. "I'm praying for a snow day."

ajadhav@post-dispatch.com | 314-809-9423

Michele Munz and Doug Moore of the Post-Dispatch contributed to this report.