Traffic

Tacoma’s Sprague Avenue-SR 16 interchange to open Sunday morning

Tacoma’s much-maligned Sprague Avenue interchange on state Route 16 will open to traffic Sunday morning, giving drivers a chance to judge the unusual structure for themselves.

Will it drive as bad as it looks?

Or, as representatives of the state Department of Transportation have been saying all along, will the unusual T-shaped design at last make sense now that all the pieces are in place?

For more than four years, the elevated intersection at the end of Sprague Avenue, which requires drivers exiting eastbound SR 16 to slow to 15 miles per hour to make a 90-degree left turn, has incited criticism of the Transportation Department.

Drivers who failed to negotiate the sharp turn left a graphic record of fender scrapings and skid marks on the concrete barriers that kept them from sailing 75 feet to the ground, a la Thelma and Louise.

Now there are ramps attached to the overpass behind those barriers, one of which connects Sprague to northbound Interstate 5, the other to southbound I-5.

The pieces are in place, and on Sunday, for the first time since the massive Nalley Valley construction project started five years ago, drivers in Central Tacoma will have close access to both directions of I-5, rather than having to detour across town.

But when the interchange opens, it will still have some idiosyncrasies.

The two new I-5 ramps are separated by just 120 feet, and each will have its own traffic signal.

The lights will be synchronized so drivers exiting SR 16 won’t have to stop twice for vehicles making left turns, but drivers will have to get used to waiting in line on the ramp.

The Transportation Department estimates that during peak morning travel times, about 18 cars will back up at a time, all of which should be cleared by one cycle of the lights.

LAST MAJOR STEP

The ramp openings are the last major step of a $500 million project intended to streamline the complex intersection of I-5 and SR 16, the busiest interchange in Pierce County.

The first phase of the project, a $184 million job that realigned the westbound half of the interchange, took 2½ years and was completed in June 2011. That phase included building 10 bridges, pouring 48,000 cubic yards of concrete, and sinking 77 supporting piers as much as 70 feet deep.

The eastbound portion of the project included moving the eastbound mainline of SR 16 and building seven bridges, including the Sprague ramps.

Public criticism of the Sprague Avenue connection began in 2010 when it was revealed that the Transportation Department made a $1 million engineering error on the eastbound SR 16 off-ramp design.

The mistake wasn’t caught until the ramp was 90 percent finished. Seven hundred feet of roadway had to be torn out, and state engineers redesigned the ramp, lowering its approach by 12 feet.

The larger Sprague design, with its unusual, elevated T shape, was a cost-saving measure originally conceived by Al Tebaldi, a traffic engineer who worked for the City of Tacoma and now works for a private engineering firm.

Tebaldi was part of a “value engineering” team created in 1999 to help come up with ideas for the interchange.

His less-expensive plan replaced a state concept that featured sweeping, multilevel flyover ramps with no stoplights.

Tebaldi said Friday that he’s not exactly feeling vindicated now that the project is finished, but said he does think people will be pleased with the I-5 access ramps.

“I think people will start to see what the initial intent was, and I think they’ll be pretty happy with the fact that they don’t have to weave or merge to get on I-5,” he said.

From a traffic engineer’s perspective, Tebaldi said, making drivers stop at the top of the eastbound SR 16 off-ramp has an advantage over a nonstop, flyover design.

“Back when I was with the city, we always had issues with traffic coming off that ramp at 50 miles an hour and then maintaining that speed on Sprague,” he said. “This will get people down to where they’re at city speeds.”

NOT WITHOUT CRITICISM

Aside from the T intersection, other aspects of the interchange have received criticism.

As drivers heading from Sprague merge left onto westbound SR 16, they immediately encounter drivers merging right to exit at Union Avenue. The high-speed weave can be treacherous at rush hour.

On the opposite side of the interchange, drivers from southbound I-5 who exit at Sprague complain that they don’t have enough room to merge safely with faster traffic coming from northbound I-5 and eastbound SR 16.

Also, the new interchange included narrowing eastbound SR 16 to two lanes at Union Avenue, forcing a merge that routinely becomes a bottleneck at high-traffic periods.

After a chorus of complaints about that earlier this year, the Transportation Department agreed to restripe SR 16, returning the highway to three lanes and requiring drivers entering at Union to yield.

The department initially planned to have that restriping finished by Sunday when the Sprague ramps open, but that’s been delayed.

The agency now says the restriping should be finished by the end of the month.

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